1228
INDUSTRIAL AND ENGINEERING CHEMISTRY
(68) Kahn, F., and Phelps, H. S., Natl. .Issoc. Corrosion Engrs., paper presented Apr. 1947. (59) Lekbera. C. H.. I n d . Gas. 25. 11. 27-9 11947). (60) Lewis, W.R., T i n and Its Gaes (Inteinatl. Tin Research Coun-
cil), KO.16, 5-7 (Sept. 1945). (61) Logan, K. H., "Underground Corrosion," Govt. Printing Office, C'irc. C450 (Nov. 27, 1945). (62) Lueck, R. H., and Brighton, K. IT., I s n . ESG.CHEY.,36,532-40 (1944). (63) Mantius, Ernest, Steel, 106, KO. 10, 69-70, 82 (1940). (64) Maxon, S. E., X e t a l Finishing, 43,148-9 (1945). (65) Miller, M. C., Elec. Light and Power, 22, Xo. 5,46-51: S o . 6, 92-4,96,99, 102 (1944). (66) AMiller. M. C., P d r o l e u m E n g r . , 17, No. 8, 55-8 (1946).
Vol. 33, No. 10
(67) ,Morral, F. R., Products Finishing, 40-2 (Jan. 1916). (68) Porter, R. TV., Chem. & Met. Eng., 53,No.4,94-8 (1946). arid Fatherly, R. L., Corrosion, 3,No. 7, 348(69) Robinson, H. 9.,
57 (1947). (70) Silnian, H., Sheet MetalInds., 21, 1031-36 (1945). (71) Timby, T. G., Iron Stcel Engr., 22,40-48 (1945). (72) Wernick, S., J . Electrodepositors Tech. Soc., 20, 47-60 (19441. Metal Inds.. 67.235-6 (1946). (73) Wernick, S., sheet Metal'lnds.: 21,443-6, 626-9 (1945). (74) Whetzrl. J. C., Metals, 15, 12-14 (1944). (75) White, J. C., Power, W.R., McMurtrie. R. L., and Pierce, Et T., Electro-Chem. Soc., Preprint, 91-2 (,4pr. 1947). (76) Wilkinson, E. R., Corrosion, 3,No. 5,252-62 (1947). (77) Wormsrr, F. E., Metal Progress. 43,223, 262, 268 (1943)
Nickel and HighNickel Alloys -
____
W. Z. FRIEND, The International Mckel Co., tnc., ,Yew Y o r k , N . I-.
L
ARGELY because of accelerated reseaxch during the war pe-
riod, new developments in nickel and nickel alloys have been more numerous during the last three or four years than in some preceding periods of similar duration. The field of nickel alloys in general is a very large one, and this summary is limited to a consideration of nickel and high-nickel or nirkel-base alloys containing more than about 50% nickel. Some of the more common high-nickel alloys now in commercial production, with their nominal chemical compositions, are listed in Table I. Mechanical and physical properties, as well as some data on the corrosion resisting properties of these materials, are given in the references shown in the table. Most of the lower nickel alloys will be covered by other authors dealing with the stainless steels and iron-base alloys, or with copper-base alloys. Considerable work has been done with high-cobalt alloys, or materials containing both cobalt and nickel which are not iron-base alloys. Since these materials possibly may not fit into other categorics, some attention is given to them in this summary. The subject matter falls naturally into three general classifications: development of new alloys or improvement in the composition of older alloys; developments in the fabrication of these alloys; and new or especially enlarged fields of application, particularly as applied to the chemical and process industries. N E W OR IMPROVED ALLOYS
HIGH TEiUPERATCRE . ~ L L O Y S . The greatest amount Of experimental work wit,h new or improved nickel alloys undoubtedly was done in the search for materials having maximum physical and mechanical properties, and oxidation resistance a t high temperatures in connection with jet engine, gas turbine, and supercharger developments (8, 15, 16, 18, 23, 31, 33,4.5, 47, 60. ?5, 88, 89, 92, 97, 99). In American developments in this field the outstanding higher nickel alloys were Hastelloy B, Inconel, Inconel B, and Inconel X. These materials were used in some models of jet engines, Hast,elloy B and Inconel S for turbine buckets or blades, and Inconel, Inconel B, and Inconel X for combustion chamber linings. I n the case of Hastelloy B and Inconel, use was made of alloys which had been in large scale production for a number of years as corrosion and heat resistant materials. Hastelloy B is an age-hardenable material, and principal improve-
ments w r e in the heat treatment of this alloy to give masiniuna physical properties a t high temperature. INCOSEL5. Inconel X is an age-hardenable nickel-chromium alloy developed particularly for jet engine and gas turbine work. and now being applied to a variety of uses a t high temperaturei. Precipita.tion hardening characteristics are obtained by additions of titanium and aluminum. For gas turbine blades it has beel! used chiefly as forgings but is available in other wrought forms such as sheet, strip, wire, seamless tubing, hot rolled rod and flats. and forged billets. .kiter suitable heat treatment, Inconel X ha.* high strength at, all operating temperatures up to 1500" F. Its merit at, temperatures higher than 1500" F. has not been explored fully as yet, but its inherent hot-hardness probably will make it useful in some forms, as in sheets, up t,o 1700' or 1800" F., or perhaps higher. Its resistnnce to oxidation is of a high order. Incone1 X shows low creep rates a t 1200°, 1350°, and 1500" F. X three-stage heat treatment is recommended for development oE maximum mechanical properties (54). INCOSEL B. Another alloy developed primarily for use in thc heat-resisting field is Inconel B, a nickel-chromium alloy now available in a variety of wrought forms. This is a modification of the older alloy Inconel, in which the chromium content is increased from 12-14% up to 16-180& Inconel B is not agehardenable but has the high level of mechanical properties whict would be expected from its chromium content. It was developed to provide increased oxidation resistance in such applications a? exhaust manifolds and heaters of heavy duty aircraft, and as combustion chamber linings of jet engines where operating temperatures continually are being pushed to higher and higher levels. It also has shown good test performance in some elevated temperature corrosion-resisting applications, such as the continuous h>drolysis of fats and distillation of fatty acids. Further investigation doubtless viill reveal other suitable applicat,ions in the hen1 resisting and corrosion resisting fields. KIMOSICALLOYS. In England considerable use was m d i . 01 the Simonic alloys in jet engine work (1, 2, 5 ) . These allo eosentia,lly of the 80 nickel-20 chromium composition, n.ith certain alloy additions to make them age-hardenable. Sirnonic 8 1 has been the standard material for blades of all Britis!i-huiIt gw turbine engines, Ximonic 75 has been used for combus:ioii ch:inibers and nozzle guide vanes.
October 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY TABLE I.
Alarm la1 \ nickel L niche1 2 nickel Z nickel 1'3 pr B 51one1 K >Ionel R RIonel K R Monel H Alone1 9 AIonel Inconel Inconel B Inconel X
Ni, %;c 99.4 99.5 93.5 98 67 66 67 66 63 63 78.5 72 min 73 d3 60 51 85 60 63 60 80 60
Cu, % 0.10 0.02
...
30 29 30 29 31 30 0.20 0.50 mas. 0.20 mas.
... 3 3
sO.\IISAL COMPOSITIONS O F Fe, % 0.15
Cr, % '
hlo, 5%
.. ..
0.05
... ...
. 1
..
1.4
0.90
1.7 0.90
..
..
2 2
6.5 9 . 5 max 7
14
22
6 ti
1';
8 3 max. 3 max.
21
...
Eaiance
..
18-18 15
18
20
15
COBALT-SICKEL-CHROJ.IIUM ALLOYS. TKO of the principal requirements for alloys to be used for high temperature gas turbine blades are load-bearing strength, or resistance to rupture, and dimensional stability, or creep resistance. Among the mattlrials showing maximum high temperature strength were alloys containing considerable amounts of cobalt as well as nickel and chromium in major proportions. A large variety of such alloys was produced and their high temperature properties thoroughly studied. . I number of these alloys which contained cobalt plus nickel in excess of about 407, are listed in Table I1 (60). The alloy most commonly used for turbine blades on jet engines and turbo-superchargers in this country was Vitallium or Stellite 21. I n the course of the investigations of these alloys a wealth of data has been obtained on such properties as tensile and yield strengths, expansion coefficients, and stress-rupture strength a t temperatures in some cases up to 2000' F. I t is to be expected that this information will be of great value to the chemical and process industlies not only from the standpoint of poir er generation but also in the design and fabrication of corrosion-resisting process equipment to operate at high temperatures and presoures. ELECTRICAL RESISTAWEALLOYS. Marked improvement was made several years ago in the life of electrical-resistance heating elements such as the 80 nickel-20 chromium and 60 nickel-15 chromium iron alloys by addition to the alloys of small amounts of such elements as calcium and zirconium, as described in patents issued to Lohr (64). Increased life of tenfold and more was reported. Somewhat similar although less spectacular effects are claimed in the patents issued to Pfeil (77) by the application of coatings containing salts of calcium, zirconium, thorium, and rare earth elements to the outside surface of these heating alloys. Z SICKEL ALLOYS. An age-hardenable high nickel alloy known as Z nickel has been regularly used for a number of years, where a material was required having the corrosion resistance of commercially pure nickel, and the very high level of strength and m e chanical properties obtainable by precipitation hardening. In order to provide a wider selection of material, two such alloys arr now being produced, one known as Z nickel, and the other as Z nickel Type B. Somewhat different heat treatments are required in age-hardening the two alloys, but the mechanical properties developed are essentially the same (53). The Type €3 material has significantly higher electrical conductivity and thwmal conductivity and a higher magnetic transformation temperature than the other alloy. L KICKEL. A low carbon variety of commercially pure nickel called L nickel now is available in all n rought forms, including L nickel-clad steel. Its carbon content is under 0.027,. I t is used in a number of high temperature corrosion-resisting applications in the temperature range of 600" to 900" F. and higher, such as molten salt heat-treating baths, fused caustic alkali production
22 32 19
..
5 32 18
1229
HIGH-NICKEL A4LLOYS
Si, 5% 0.05 0.15
LIn, R 0.20 0.20
0 . io
1 0.85 I.1
...
0.50 0.05 0.50 3 4 0.25 0.50 max. 0.40 1
1
1 1I) 1 1 1 .,.
..
0,85
0.75 0.75 0.25 1 mas. 0.50
C. 4; 0.1 0.02 mas. , .
u . is
0 15 0.10 0.30
0 .i n 0.10 0.08 0.15 0.04
04
Otllrr
.
Rtferencev
.
.. ..
41 2 . 7 5
.....
9 1 2.75
41 CJ.7d: ' i'h 1; Ti2.5
..... (54)
.....
2 1
1 1 1 1
1
..
\T I
.
3 A1 1 1
w
0 , 15 mas. 0.07 mas.
and U Y ~ and , other applications in this temperature range where regular -4nickel sometimes is subject to intergranular attack and embiittlement. Because of its relative softness, L nickel also is applied to severe stamping, drawing, and forming operations and i t 3 tubing which must undergo considerable cold bendlng, as in carhonated water and beer cooling coils, L nickel toroidal joints are used in the high pressure combustion chamber inlet of a gas turbine (31). CHLORIXET ALLOYS. Fontana (36)has described the development of two high strength cast alloys, knoivri as Chlorimet 2 and Chlorimet 3, for use under a number of extrclmely corrosive conditions. Chlorimet 2 is a nickel-molybdenum alloy containing approximately 63% nickel and 32% molvbdenum. I t has good resistance to hydrochloric acid of all Concentrations and temperatures. I t is recommended for use with all concentrations of SUIiuric arid up to about 176" F. and for concentrations up to about 6 0 7 at boiling temperatures. Chlorimet 3 is a nickel-molybdenum-chromium alloy containing approximately 60% nickel, molybdenum, and 18% chromium. I t IS particularly u d u l for handling wet chlorine and hypochlorites and for certam other oxidizing conditions. I t is resistant to sulfuric acid solutions up to 35% in concentration a t temperatures up to about 176" F. and to a variety of acid chloride salts (321. The Chlorimet alloys so far are available urily in cast form, and are applied chiefly as pumps and valves. Best corrosion resistanc'e and machinability are obtained with these alloys by heat treatment a t 2050' F. followed by water quenching. Chlorimet 2 can be age-hardened at 1290' F. to a hardness of about 500 Brinell. SICKELIRON ALLOYS. .1 recent advancvment described by Nudge and Talbot ('72) in the field of controlled expansion alloys is the development of age-hardenable iron-nickel-titanium alloys the Invar and Elinvar types, which can be fabricated readily, m d , with cold working of the order of 35 to 50% followed by aging, can be produced to have desirable expansion and thermoelastic characteristics with increased strength and hardness. The materials are k n o r n commercially as Si-Span alloys. Chemical compositions are given in Table 111. Xi-Span Lo alloys are used in applications requiring a low COefficient of thermal expansion and high strength. A common application is as one of the elements of bimetal strip used in thermostats. They are also used in instruments and other equipment ansion components are essential, such as measuring springs, instrument frames, glass-to-metal seals, and machine parts. Xi-Span Hi, a high thermal expansion alloy, is used primarily for thermostatic controls, usually as one element of a bimetal. I t is used also in combination with other high-expansion alloys where similar expansion rates are required, The advantage of the pre-
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
1230 TABLE 11. Alloy Designation
r\'OiVINAt
Vol. 39, No. 10
CHEMICAL COMPOSITIONS OF SOJIE COBALT-NICKEL ALLOYS FOR HIGHTEMPERATURE SERVICE
Ni, % 20 20 20 42 37 2 33 20-30 15Li6.5 10-12
Co, 70 20 20 44 22 22 64 33 20-30
Cr, % 20
Bal.
28 26-28 25-28
49.5-51.0 54-55
20
20 18 18 27 26 25-35
Mo, 70 3 4 4
.. 3 5 5
.. .. 6 ..
cipitation-hardening alloys in this application are added strength, resistance to thermal and mechanical shock, and improved properties a t elevated temperatures. Xi-Span C, a constant modulus alloy, is used primarily in instruments and machines for parts which must have no change or a controlled change in elastic characteristics with changes in temperatures. Specific uses include springs for accurate scales, tuning forb, Bourdon tubes, diaphragms for altimeters, strain gages, and proving rings. A variety of nickel-iron alloys containing from 48 to 80% nickel are used in electrical and communications equipment where a high degree of magnetic permeability is required, as in transformer cores. Recently a new alloy of this type was announced by Boothby and Bozorth (20)which has been named Supermalloy. It contains 79% nickel, 15% iron, and 5% molybdenum and is wid to have an initial magnetic permeability of 100,000and maximum permeability of 800,000. It has found useful application in the form of 0.001-inch and O.OO4inch tape, insulated and formed into transformer cores. FABRICATION
WELDING. There have been continued improvements in the techniques of welding the high-nickel alloys, and most of these materials can be welded satisfactorily by all of the common welding processes. Chisholm (28) reported the results of an investigation of Hastelloy welding by Union Carbide and Carbon Research Laboratories. With Hastelloys B and C, heat treatment after welding usually is not required to maintain full corrosion resistance except under the most corrosive conditions, as in handling boiling 20% hydrochloric acid with Hastelloy B or wet chlorine gas with Hastelloy C. Under these conditions heat treatment is desirable. With Hastelloy A it is preferable to anneal after welding to avoid accelerated attack in the heat-affected zones adjacent to welds. Alloys A and B are annealed at a temperature of 2100" to 2150' F. followed by rapid cooling; alloy C is annealed a t 2200" to 2250" F. and cooled rapidly. Cracking in the welding of these alloys can be prevented by avoiding excessive stresses on these materials in the temperature range from 1200' to 1800' F. where their ductility is lowest. Gallaher (41), Chenicek, Iverson, Sutherland, and Weinert (27),and JIenaugh (69) described experiences with the lining of steel vessels with Hastelloy alloys A and B for use as isomerization reactors in petroleum refineries. More that forty such vessels were Hastelloylined, both plug and strip welding being used. These included vessels as large as 7 feet in diameter and 90 feet high operating under 250 pounds per square inch gage pressure. Hastelloy A linings are subject to intergranular deterioration a t steel stressrelieving temperatures, so that Hastelloy B linings are preferred. Welded linings of this alloy also are applied to valves, pipe, and fittings. Considerable use has been made of metallizing or spray coating processes in the lining and repair of valves used in corrosive environments. This is particularly so in the petroleum industry, where applications described by Looney (66) include: steel plug valves coated with Monel and with Stellite 6 for hydrofluoric acid
Fe, % Bal. Bal, 4 13 Bal. 2 1
...
...
1 0.60
Si. % 0.50
0.50-0. G5 0.50-0.65 0.40 0.65 0.25 0.25
%In,% 1 0.75-1.60 0.50-0.75 0.70 0.70 0.30 0.30
, .
..
0:i;
0 :30
c, % 0.15 0.40-0.45 0.40 0.05 0.03 0.30 0.40
..
0.40-0.50 0.40-0.50 0.40-0.60
Other, % W 2 ; Cb 1 W 4 ; Cb 4 W 4 ; Cb 4
Ti 2 T i 3 ; A10.30
....... ........
W 15-25; B0.25-1 0
........ ........
IF. 7-7.5
service; steel plug valves coated with Hastelloy B for hydroch!oric acid service; and steel valves coated with Hastelloy alloy for use with 65y0sulfuric acid a t 300' F. Tests are being made with metallized pipe fittings with alloy coatings thick enough to take pipe threads. A newly developed powder weld process, in which the alloy is fed to the spray equipment in the form of a fine powder, was used in the application of a hard-surfacing material, Colmonoy No. 6, having high nickel content with chromium boride crystals (65). The novelty claimed for the process lies in the fusion bonding of the sprayed coating a t temperatures between 1850' and 2050' F. to secure tight adhesion and freedom from porosity. Sprayed metallic coatings have so far not been applied very generally to corrosion resisting equipment of large area where the costing material is cathodic to the base material, because of a tendency to porosity They have worked satisfactorily in the surfacing of flange faces, valve parts, and other relatively small parts which can be heat treated a t high enough tempcratures to fuse or homogenize the coating after application. A newly developed powder-cutting process, utilizing a flame of finely divided iron-rich powder and oxygen, is being applied to the cutting and scarfing of nickel, Monel, Inconel, Hastelloy, and stainless steel plate (35). A newly developed fluorine-hydrogen torch can be used for welding Monel, nickel, and copper (83) An improved electrode of high-nickel alloy is used widely for making strong machineable welds in cast iron (6). PRECISIOS CASTINGS. Practically all of the high-nickel alloys are now produced as precision castings. A notable achievement in this field was the mass production of several million such castings of Vitallium and other Stellite and Hastelloy alloys for turbine blades and other parts of jet engines (9). The methods and equipment used by Haynes Stellite Company in this work was described by Geschelin (43). Sweeny (90) gave design data for these materials, dealing with such factors as weight and dimensional limitations on sizes of precision cast parts, tolerances, and types generally suited for manufacture by this technique. A particulsr advantage of this method is the production of small precision parts of materials such as Stellite alloys and 9 Monel, which are difficult to machine because of their hardness. SINTERED NICKEL. Some advances have been made in the powder metallurgy of nickel and high-nickel alloys, as with a number of other metallic materials. Price (81) presented a review of the literature on the powder metallurgy of nickel and some of its alloys under the headings: preparation and nature of powder, effect of pressure, effect of sintering conditons, mechanical and physical properties, and industrial applications. Sintered nickel is used in high vacuum tube work because of its exceptional purity. In this case it is used in the form of fine wire, sheet, or tubes. Schlecht and Tregeser (85) described the production of sintered billets of carbonyl nickel weighingover 1ton for subsequent rolling into large sheets for cladding steel. Among the most interesting applications have been the uses of pcrous sintered nickel for filters and diffusion diaphragms. A small sintered nickel cupshaped filter formed a vital part of a proximity fuse where the performance of the delayed action mechanism was governed by the time taken for mercury to seep through the cup (14). Density of the cups varied less than 1% over a production run of millions.
INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1947
In Germany sintered nickel filters \\ere used for the purification of concentrated cuustic soda solutions (86). The degree of po-
rosity was accurately controlled, and filter plates 150 mm. in diameter and 1 mm. thick have been preparcd from sintered nickel. Such filters are capable of filtering 2 toils of hot 50% sodium hydroxide in 6 to 8 hours. The filters can be cleaned by rinsing R ith water and blowing air through them in the reveise direction. When greater strength is required the filters are prepared by sintering the poFvder over mesh reinforcements. Additiona! applications for porous metal filters and diaphragms were suggested by Lennox (63). CLADSTEELS. Increased use is being made of steel plate clad on one or both sides with nickel or one of the high nickel alloys, for corrosion resisting equipment, especially where the total plate thickness required for structural reasons is such that a saving can be effected over the solid nickel or alloy. Cladding is done by several means including hot rolling, spot u elding, and weldedoverlay. Rlonel-, nickel-, L nickel-, and Inconel-clad steels are produced regularly by hot rolling, and some experimental work has been done on Hastelloy B cladding by this method. These and other rolled nickel alloys can be applied as cladding by the welding methods. Descriptions of the hot-rolling methods for cladding steel were given by Wick (95) and by Gosnell (44). The latter author also provided a comprehensive review of applications of nickel-, Monel-, and Inconel-clad steels in the chemical and process industries. A large nickel-clad steel petroleum refinery vessel was built of 3 3 / ~ i n c hplate with 10% nickel cladding. Of particular interest is the use of clad steels for tube sheets of evaporators and heat exchangers with both rolled and welded tubes. Sickel-clad steel tube sheets and side sheets are being used in locomotive boilers, in some cases in conjunction with Monel stay bolts (51) A recent development is the production of thin nickel and Monel-clad steel strip with cladding on one or both sides ( 7 ) . In the cold-rolled condition it is available in thicknesses between 0.01 and 0.125 inch. Hot-rolled, it is available in thicknesses between 0.095 and 0.25 inch. Standard thickness of cladding is 10?&
NICKELPLATING. Heavy nickel plated coatings are now used frequently for corrosion resistance in process equipment. Such coatings, when properly applied and of sufficient thickness, have the same degree of corrosion resistance as solid nickel. Normal plating thicknesses of 0.003 to 0.010 inch are employed, depending upon the nature of the application. X range of hardnesses from about 140 to 400 Vickers and of tensile strengths from 50,000 to 155,000 pounds per square inch can be obtained for the as-plated nickel deposit, depending upon the type of plating solution used (84). Blum (19) referred to two outstanding applications of nickel plating in the Manhattan project: development of methods for applying thick impervious coatings of nickel to the inside of pipes and other process equipment and production of nickel screens by electrodeposition. Other examples are the use of vacuum tomato cooking pans with inside surfaces nickel-plated 0.010 inch thick, and the use of paper and plastic sheet-finishirig rolls with plated nickel surfaces as much as 0.030 inch thick Internally nickel-plated tank cars have been used for transportation of caustic soda. Internally nickel-plated pipe and fittings now are regularly available in sizes from 2 inches upward. To combine the light features of plastic and impregnated n m d wnstruction with the properties of metalhc surfaces, nickel phi -
1231
ing of plastics presents several new opportunities for the creative mind. The nonconducting materials are rendered conductive by chemical reduction of a metal on the surface, or by adding powdered metal or graphite to a lacquer applied to the surface. After plating, the deposit provides a metallic covering which nidv be soldered, polished, or made an electrical conductor in addition to riiaking the plastic more rigid and eliminating moisture absorption and tendency to warp. Nickel-plated wood airplane propellers are produced by applying, to a preformed wood blade core, an electroplate of controlled thickness ( 3 ) . In some cases parts are fabricated complett4y by electroforming (as). The process results in the formation of the entire unit by electroplating upon a removable mold of low melting alloy or sensitized wax. High unit strengths and close tolerancrs are obtained. Recently a nickel structural unit weighing 70 pounds was electroformed to a thickness of l/z inch. This technique is being applied to the manufacture of nickel plastic dies, where a high finish and exact duplication are needed in a corrosion resistant material. Complex radar wave guides, exactly dimensioI1t.d searchlight reflectors, and Venturi tubes are other examples. Fine mesh screens are being produced on continuous machines Old established uses are electrotypes and phonograph record master and stamping plates. TUBING.Since the installation of a 4000-ton horizontal hydraulic press a t the Huntington, W. Va., works of The International Sickel Company, Monel, nickel, and Inconel have been available in this country in the form of extruded tubing and round rods. Tubing up to 8 inches diameter with wall thicknese up to ’ / a inch have been produced by this method. The extrusion equipment and its method of operation were describctl In Brown (22) and by Lorant (67). Use now is being made of “duplex” or bimetallic tubing, where n tube of one metal or alloy is drawn within or over a tube of another material t o provide resistance to different corrosives on opposite surfaces. Most applications have been to heat exchanger tubes. Most of the high-nickel alloys, available in the form ol tubing, can be adapted to this type of construction when requirccl Information on the heat transfer coefficients of duplex tubes of various combinations is being developed. APPLICATIONS
FLUORINE. The subject of fluorine chemistry has received tl great deal of attention, as indicated by number of papers dealing with the subject preEiented a t the Symposium on Fluorine Chemistry a t the Chicago meeting of AMERICAN CHEMICAL SOCIETYin September 1046 (91). In view of the extreme reactivity of fluorine and safety hazards involved, the selection of suitably resistant metals and alloys is an important consideration. Nickel and Monel are among the most resistant materials a t elevated temperatures. Corrosion tests reported by Landau and Rosen (62) show these materials to be resistant t o fluorine a t 930” F. and nickel probably is useful a t somewhat higher temperaBures if the protective nickel fluoride film is not removed continuously by abrasion or otherwise. If these metals are contaminated with grease or other organic materials in the presence of fluorine, firing may occur because of the heat of reaction of fluorine with the organic material. Sickel cylinders are used for the storage of fluorine at pressuree
TABLE 111. RANGEO F CHEMICAL CoMPOSITIOX O F Ni-SPAN ALLOYS Alloy Xi-Span Xi-Span Ki-Span Ni-Span Xi-Span
Lo 42 Lo 45 Lo 52 Hi
C
xi, % ’ 40.5-42.6 44.6-46.5 51.0-53.0 28.0-30.0 41.0-43.0
Ti, %
2.2-2.6’ 2.2-2.6 2.2-2.6 2.2-2.6 2.2-2.6
Cr, %
..... ..... .....
8.0-9.0
5.1-5.7
C (Max.), % 0.06 0.06 0.06 0.06 0.06
A h % 0.3-0.6 0.3-0.6 0.34.6 0.3-0.6 0.3-0.6
Si, % 0.3-0.8 0.3-0.8 0.3-0.8 0.3-0.8 0.3-0.8
AI, %
0.4-0.8 0.4-0.8 0.4-0.8 0.4-0.8 0.4-0.8
P (Max.), 8 (Max.), %
%
re, %
0.04
0.04 0.04 0.04 0.04 0.04
Bal. Bal. Bal. Bal. Bal.
0.04 0.04 0.04 0.04
1232
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
up to 400 pounds per squaie inch gage, Packless Monel valves of the diaphragm or bellows-sealed type are used for handling fluorine a t pressures up to 100 pounds, and Alone1 needle valve< packed with Teflon or its equivalent with pressures up to 400 pounds. Diaphragm pumps with Monel diaphragms and heads, nickel disk suction valves, and K Monel cone discharge valves were used for compressing fluorine to 50 pounds per square inch gage (74). Several cases of the use of Monel or nickel rcactors in carrying out organic fluorinations were cited in papers includd in the A.C.S. symposium. In the construction of electrolytic cells for generation of fluorine, illonel was used for diaphragms and in some cases for cathode and cell box (37). Nickel anodes were thoroughly tested but i l l general provpd less suitable than anodes of carbon or of carbon impregnated with copper for continuous operation (78). Sickel anodes have the advantages of operation with wider variation ut temperature and hydrogen fluoride concentration, and sturdier e rthe and more rugged construction, and the presence of ~ ~ a t in electrolyte does not interfere with operation. Howevcr, they have the disadvantages of low current efficiency (60 to 75c2) and the fact that they corrode gradually with loss of nickel and formation of a troublesome sludge in the electrolyte. In some case6 cells are started with nickel anodes to overcome the initial polarization encountered with carbon anodes and are then shifted over to the latter for continuous operation. In a description of electrolytic fluorine production in Germany, K'eumark (73) pointed out that nickel anodes had performed satisfactorily in fluoride crlk operating a t temperatures below 150' C. CHLORINEASD HYDROGEN CHLORIDE. Considerable ube ha5 been made of nickel and None1 equipment in organic chlorinations, and other processes involving the use and handling of chlorine or of hydrogen chloride under essentiallyanhydrous conditions. Such processes include the chlorination of benzol, phenol, aniline, and other aromatics; methane, ethane, acetylene, paraffin, and other aliphatics; and a variety of organic reactions, except those in which condensed water is present or is formed as a product of the reaction. The corrosion test data presented by Brown, DeLong, and Auld (21) and by Friend and Knapp (39) show that nickel and high-nickel alloys are among the materials most resistant to chlorine and hydrogen chloride a t high temperatures. Nickel, the most resistant of these materials, is useful for continuous service a t 1000" F. Use is made of sulfur-free carbon-lined nickel tubes for chlorination reactions a t 1500' F. In another case a water-jacketed nickel tube is used in handling chlorine gas a t an inlet temperature of 2000" F. (SO). HYDROCHLORIC ACID. In isomerization processes, such as the conversion of normal butane to isobutane, aluminum chloride plus hydrogen chloride is used as a catalyst. Where a significant amount of moisture is present in the charging stocks, corrosive conditions are likely to be severe in the contacting towers and separating equipment, where a liquid catalyst complex or tar is encountered. Such equipment has been lined with Hastelloy -\ or Hastelloy B, the latter alloy being preferred because of superior corrosion resistance (67). The results of corrosion tests in isomerization equipment were presented by Morton ( 7 I ) , and by Chenicek, Iverson, Sutherland, and Weinert (67). Somelvhat similar results have been experienced in the production of ethylbenzene using the same catalyst. Where sufficient dehydration of charging stocks can be accomplished, or where suitable corrosion inhibitors are added, nickel- and Monel-lined reaction equipment has proved satisfactory. In one refinery a large nickel-clad reactor for isomerization of naphtha was lined with reinforced Imnnite cement a t points where corrosive conditions proved too severe for nickel ( I S ) . The increasing salt content of some crudes has resulted in severe corrosion of steel equipment in crude topping towers in a number of refineries because of the dilute hydrochloric acid formed by hydrolysis of the brines. This problem has been overcome b.ithe installation of Monel linings and bubble caps and plates in
Vol. 39, No. 10
rop parts of such towers and for reflux condensers, accumulators, and run-down lines (71). Where sulfur is present the use of \Ionel is limited to locations where temperatures do not exceed about 500' F. The lower portions of crude distillation towers where temperatures exceed 500' F. usually are lined \+ith stainless steel. Nickel and high-nickel alloys in general are applied to a wide variety of hydrochloric acid condtions, Hastelloy alloys A and B and Chlorimet 2 alloys for strong hot solutions, and nickel and \lone1 for more dilute solutions. HYDROFLUORIC ID. The adaption of hydrofluoric acid alkylation processes for production of iso-octane has necessitated the handling and production of this acid in volumes much larger than ever handled previously. hfonel equipment mas used to a conYiderable extent for hydrofluoric acid regenerating and dehydrating equipment in alkylation plants as well as for heaters, valves, pumps, piping, bolts, gaskets, packing, and miscellaneous fittings where hot solutions of this acid were encountered. The applications and performance of RSonel in alkylation plant equipment n ere described by Holmberg and Prange (60), Prange and Findlay (80), and others (78). The results of laboratory corrosion tests of Alone1 and other high-nickel alloys in hydrofluoric acid solutiolis and the results of corrosion tests in hydrofluoric acid regeneration equipment of operating plants were presented by Friend and Teeple (40). S Monel, because of its resistance to galling or seizing, is used for nonlubricated plug valves and pump parts. The use of Monel valves and agitators in the productioii of hydrofluoric acid and fluorides, and of Monel rotary driers for zinc Qilicofluoride,is referred to by Callaham (26). None1 evaporator chest5 with Hastelloy C tubes are used in the concentration of ammonium, magnesium, and zinc silicofluorides. Highly jtressed Rlonel, such as cold drawn tubes or rod, may be subject to stress corrosion cracking in strong silicofluoride solutions and should be stress-relieved a t 1000' F. before exposure (58). SULFURICID. Corrosion by sulfuric acid has always been somewhat of a problem in petroleum refineries. In the customary acid-treating processes Monel is used for treaters and for acid sludge lines, pumps, and valves. R7iththe development of sulfuric acid processes for alkylation, polymerization of olefins, and production of alcohols from refinery gases, it has been necessary to handle sulfuric acid in the most corrosive concentrations of 40 to 60% at temperatures up to 275" F. and higher, and to install equipment for concentrating these solutions to 93 to 96% for reuse. Operating experience described by Wilkinson (96) indicates that Monel in some cases may be satisfactory for parts of valves and pumps handling 40 to 60y0 acid up to 240' F. but not for higher temperatures. Hastelloy D is used for handling hot solutions a t higher concentrations and particularly for heater tubcc in sulfuric acid concentrators (25). I t can be used with steam pressures up to 300 pounds per square inch. Recent experience has shown that Hastelloy D may suffer arcelerated attack in boiling sulfuric acid of 55V! concentration. Recent work by Wachter, Treseder, and Weber (93) showed that arsenic compounds are potent inhibitors of corrosion of steel in sulfuric acid solutions, and a few tests with Monel in 71y0sulfuric acid indicated that arsenic compounds also may act as possible inhibitors lor this alloy. Current developments in the production of various surfaceactive agents, including detergents, emulsifiers, wetting agents, and penetrants, by sulfation and sulfonation of a variety of organicmaterials, have required the use of high-nickel alloys for processing equipment. Monel in particular is used for sulfating, washing, and neutralization equipment where 93 to 9870 sulfuric acid is the sulfating or sulfonating agent, and where the acid may become diluted to concentrations too corrosive for the use of steel or cast iron. The use of Monel sulfonating equipment has so far been limited to reaction temperatures below about 240' F. Use is made of Monel and of nickel- and Inconel-clad 3teels in the storage arid handling of sodium alkyl aryl sulfonates and sodium
October 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
alkyl sulfates. Inconel-clad steel towers are used for spray drying the latter materials. CAUSTICSODA. An important application of nickel and nickelclad steel for years has been in the evaporation and handling of hot strong caustic soda and caustic potash solutions. Recently there has been interest on the part of caustic producers and some users in the extension of continuous processes to the evaporation of these alkalies to 90 to 98V0 concentration, at temperatures of 600" to 900" F. and higher, formerly done mostly by batch operation in cast iron pots. L nickel and L nickel-clad steel have so far shown good performance in these fused caustic applications, except where the chlorate content of electrolytic caustics is high or n here sulfur is added for shading. The lox carbon L nickel is preferred for this application because apparently it is not subject to embrittlement or cracking a t welds or other stressed areas, n hich sometimes may occur withunstress-relieved h nickel in fused caustic. A continuous L nickel-clad steel evaporator equipped with L nickel-clad steel heater tubes, gas-fired internally, has been in constant use for several years, evaporating low chlorate caustic soda from 72 to about 95% Concentration. Signifir.ant corrosion of L nickel has occurred only a t the firing end of heater tubes, and these tube sections have to be replaced a t iiitervals which are great enough to be entirely economical. Recent aervice tests indicated that properly heat treated Inconel heater tubes may be more resistant than L nickel, and this investigation is being continued. Nickel-lined tanks are used for holding molten sodium hydroxide containing 2% sodium hydride in this process for pickling stainless steels and other allovs (11). The bath temperature is 800' to 82.5' F. Monel and nickel liners and heater tube3 are used in equipnient tor the regeneration of caustic solutions used in treatment of petroleum products where steel equipment is subject to caustic rmbrittlement. Methods used in the application of such lininpP are described by Evans and Meyer (34) and by others (52). HEATRESISTANCE.In view of the work done with high temperature alloys it is nor surprising that increased applications of nickel and high-nickel alloys have occurred in the construction of rquipnient for heat resistance and heat treating. Inconel has Yhown particular usefulness in this field, where a sheet or tubular material is required, because of its resistance to oxidation and its yield and creep strength a t high temperatures. It is used for such equipment as exhaust manifolds of aircraft and heavy duty trucks, aircraft cabin and de-icing heaters and fire walls, covers of electrical resistance heating elements, and thermocouple protection tubes (10, 59). For heat treating equipment it is applied to a variety of uses a t temperatures up to 2100" F., including tubes and muffles of annealing, brazing, and sintering furnaces; retorts. baskets, and racks of carburizing and nitriding furnaces; enameling fixtures; and hearth rolls, rails, and roofs of heat treating furnaces. The other nickel-chromiurn alloys, such as the 80 nickel-20 chromium and 60 nickel-15 chromium alloys, also are used in qome of these applications. Under reducing and sulfurtree conditions and a t very high temperatures, for which resistance to scaling is more important than creep strength, nickel aometimes is preferred to Inconel because of its higher melting point; useful service has been obtained at 2300" F. A significanr contribution to the development of heat resisting alloys &-asthe electron diffraction study of oxide films formed on alloys of iron, cobalt, nickel, and chromium at temperatures from300' to 700' C. by Hiclunan and Gulbransen ( 4 9 ) . Among the high nickel alloys studied were Inconel, Nichrome V, Stellite 21, Hypernik (49 Fe, -19Xi, 2 >In), Kovar (54 Fe, 18 Co, 28 S i ) , and Refractalloy. Among the conclusions drawn from this work were (a) iron and chromium ions diffuse more readily to the surface than the other metal ions; (bj nickel oxide is never observed on the surface of its alloys even when present in large percentage, as in Inconel and Sichrome V; and (c) cobalt oxide, if observed, appears only a t low temperatures. The same authors also studied the oxide films formed on a number of pure metals including nickel (46).
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MISCELLANEOUS. Inconel-lined or clad reaction towers are used for the continuous countercurrent hydrolysis of fats a t temperatures of about 500" F. and pressures up to 750 pounds per square inch gage. Inconel also is used for distillation and heating equipment for the continuous vacuum distillation of fatty acidu and tall oil. In petroleum production equipment increasing use is being made of high-nickel alloys, particularly in production fields such a i \Irest Texas, where high sulfur crudes are encountered. Among the applications described by Morton (70) are: K Xonel and nichel-plated steel sucker rods, Monel polished rods, and K Monel balls, drops, and seats of oil well pumps; and Monel bellows diaphragms and K None1 seats and wires for gas-lift equipment. The use of nonmagnetic I< None1 drill collars on equipment for controlled drilling of wells was described by Kothny (61). Sickel and nickel-lined shipping containers have found increasing use for transportation of chemicals for which steel is not suitable. imong the chi,micals handled in nickel cylinders or drums are fluorine, nitrosyl chloride, phosphorus oxychloride, phosphorus trichloride, and benzyl chloride. Among the product. shipped in nickel-Lined or clad tank cars are phenol, gin, neutral spirits, 757, caustic soda, ethylene dibromitie, phosphorus o\y. chloride, phosphorus trichloride. tiitrosyl chloride, and othcr halogen compounds. considerable amount of nickel and high-nickel alloys wciii into special equipment used in the various atomic energy developments (121, most of which has not been described. The uw of piping of Hastelloy alloys B and C at the Oak Ridge plant is r e ;erred to by Schrader and DeHaan 187). Hastelloy B is used for solutions containing high concentrations of hydrochloric or hypochlorous acid and other chlorides, whereas Hastelloy C is used where oxidizing agents, such as nitric acid or ferric chloride, are present. Inconel is among the materials used in incinerating and calcining furnaces operating a t temperatures From 1300' to 1650' F. in oxidizing atmospheres containing nitrogen dioxide, sulfur dioxide, and small amounts of hydrogen chloride. Neutron absorption values of several conat rurtinn materials including nickel are given by Wheeler ( 9 4 ) . LITERA'IWKE CITEL,
-hiouyiilous, Aeroplane, pp. 279-82 (Sept. 6, 1946). Anonymous, Automotire and Al;htion Inds., 95, No. 5, 28-33, 70, 74 (1946).
-Inon>-mous,Aviation, 45,No. 5 , 123 ( M a y 1946). Anonymous, Elec. Mfg., 35,KO,3, 115-18, 196, 198, 200 (39451. -Inonynous, Flight, 49,336-40 (1946). Inonymous, I r o n Age, 156,No. 20, 122-3 (1945). Ibid., 159,No.4, 139 (1947). dnonymous, Machinery, 52, No. 11, 183-7 (1946). Anonymous, Materials & Methods, 23, 1016 (1946). Ibid., 25, No.4, 143 (1947). Anonymous, Metal Progress, 51, 949 (1947). Anonymous, Northern M i n e r , 31, 16 (Aug. 16, 1945,. -Inonymous, Petroleum Procewing, 1, No. 2, 140-4 (1946). .lnony-nious, Steel, 118, No. 16, 84-5, 132 (1946). Badger, F. S., Jr., Cross, H. C., Evans, C. T., Jr., Frankb, R., Johnson, H. B., iMochel, N. L., and Mohling, G . , Metal Progress, 50, No. 1, 97-122 (1946).
Badger, F. S., Jr., and Sweeney, W.O., JI,.; Cross, H. C., and Simmons, W. F.; Cross, H. C.; Freeman, J. W.,Reynolds. E. E., and White, A. E., "Symposium on Materials for Gas Turbines," Am. SOC.Testing Materials (1946). Betty, B. B., and Mudge, IT"' A., Mech. Eng., 67, 123-9 (F'eh. 1945).
Binder, W. O., I r o n Age, 158, No. 19, 46-52 (1946). Blum, IT., Metal Finishing, 45,No. 1, 66-8 (1947). Boothby, 0. L., and Bosorth, R. M.,B u l l . Am. Phys. SOC.,22. NO. 1, 18-19 (1947). Brown, M. H., DeLong, TT. B., and Aluld, J. R.. TND. ENG. CHEM.,39, 8 3 9 4 4 (1947). Brown, H. M.,Machinery, 51, No. 8 , 162--9 (1945). Browne, L. E., Steel, 118, S o . 21, 88-91, 132 (1946). Burgess-Parr Co., Bull. 105 and 105-A (1946). Burke, J. F., and Mantius, E.. C h m . En.0. Progress, 1, 237-46 11947).
INDUSTRIAL A N D ENGINEERING CHEMISTRY
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(26) Callaham, J. R., Chem. & Met. Eng., 52, No. 3 94-9 (1946). (27) Chenicek, J. A., Iverson, J. O., Sutherland, R R and Weinert. P. C., Chem. Eng. Progress 1, 210-18 (1947). (28) Chisholm, C. G., Welding J., 25, 1179-82 (1946). (29) Clauser, H. R., Materials & Methods, 24, 112-16 (1946). (30) Cromther, J. F., private communication, 1947. (31) Cunningham, J. F., Jr., Metal Progress. 48, 484-8, 526 (1945) (32) Duriron Co., Bull. 111 and M-4 (1946). (33) Evans, C. T., Jr., Metal ProgTess, 48, 1083-95 (1945). (34) Evans, D. E., and Meyer, W.B., Petroleum Refiner, 23 455-i (1944); Welding Engr., 31, No. 3, 38-40 (1946). (35) Fleming, D. H.. Materials & Methods, 25, No. 2, 73-6 (1947). (36) Fontana, R.I. G., Chem. Eng.,53, No. 10, 114-15 (1946). (37) Fowler, R. D., Burford, W. B., Anderson, H. C., Hamilton, J. &I., Jr., and Weber, C. E., IND. E m . CHEM.,39, 266-71 (1947). (38) Fraser, 0. B. J., “Symposium on Stress-Corrosion Cracking of Metals,” Am. SOC.for Testing Materials and Am. Inst. Mining Met. Engrs., p. 466 (1944). (39) Friend, W. Z., and Knapp, B. B., Trans. Am. Inst. Chem. Engrs., 39, 731-53 (1943). (40) Friend, W. Z., and Teeple, H. O., Oil Gas J . , 44,87-101 (March 16, 1946). (41) Gallaher, J. A,, Petroleum Refiner, 24, No. 4, 106-13 (1945). (42) Gardner, E. P. S., Welding, 14, 150-5 (April 1946). (43) Geschelin, J., Automotive Aviation Znds., 94, No. 8, 20-23, 108 (1946). (44) Gosnell, E. C., Corrosion, 2, 287-306 (1946). (45) Grant, N. J., I r o n Age, 157, No. 21, 42-8; No. 22, 50-6; No. 23, 77-80; NO. 25, 60-3 (1946). (46) Gulbransen, E. A., and Hickman, J. W., Metals Techno!., 13, 1-26 (Oct. 1946). (47) Halford, F., Aeroplane, 70, 544-5 (1946). (48) Haynes Stellite Co., “Hastelloy High-Strength Kickel-Base Alloys for Corrosion Resistance,” 6th ed., 1940. (49) Hickman, J. W., and Gulbransen, E. A,, Metals Technol., 13, 1-27 (Oct. 1946). (50) Holmberg, M. E., and Prange, F. A , , IND.ENG.CHEM.,37, 1030-3 (1945). (51) Huston, F. P., R y . Mach. Engr., 119, No. 2, 64-5 (1945j. (62) International Nickel Co.. Inc., Mech. Letter 8 (Dec. 1945). (53) International Nickel Co., Inc., “Engineering Properties and Heat Treatment of ‘Z’ Nickel,” Dec. 1946. (54) International Nickel Co., Inc., “Inconel ‘X,’ A High-Strength. High-Temperature Alloy,” data sheet (Jan. 1947). (55) International Nickel Co., Inc., Tech. Bull. T-5 (Oct. 1946). (56) Zbid., T-7 (Apr. 1946). (57) Ibid., T-9 (Aug. 1943). (58) Zbid., T-15 (Oct. 1946). (59) Kline, E. M., and Hall, A. M., Metals & Allozls, 21, 401-3 (19451. (60) Knight, H. A., Materials & Methods, 23, 1557-63 (1946). (61) Kothny, G. L., Oil Weekly. 30-3 (Jan. 20, 1947); 36-9 (Jan. 27. 1947) ,
a
Vol. 39, No. 10
(621 Landau, R., and Rosen, R., IND. EXG.CHEM,39, 281-6 (1947) (63) Lennox, J. W., I n d . Chemist, 20, 600-4, 615 (1944). (61) Lohr, J M., U. S. Patents2,019,686, 2 019,687, 2,019,688 ( S o l 5 1935). (ti5) Long, C. J., and Rich, T. E., Welding J., 25, 744-5 (1946) (66) Looney, J A., Petroleum Processing, 1, No. 4, 290 (1946). (67) Lorsnt H , Machinery, 53, No. 11, 170-1 (1947). (681 McCurdy, l? T , Trans. Am. Soc. Testing Materials, 39, 69h (1939). (60) Tienaugh, T. H , .Ifaterials &. Methods, 23, 1289-92 (1946) (701 Morton E R Corroszon, 3, 23-34 (1947). (71) J I o i t o n U B Tranq Am. Soc. Mech. Engrs., 68, 229-35 (1946 (72) M u d g t , 11’ A and Tal bot, A. M., Iron A g e , 157, No. 17 66 -7~1 (1946) (73) Neumark, H. R., “Electrolj tic Fluorine Production ,n Ger many,” Electrochem. Soc. (Toronto), Oct. 16-19 1946. (74) Osborne, S. G., and Brandegee, M. M., IXD.ENG.C H E X ,39 2 7 3 4 (1947). (75) Peteis, F. P , Sci. American, 174, KO. 4, 152-4 (1946). (76) Pfeil, L., U. S. Patent 2,412,058 (Dec. 3, 1946). (77) Pfeil, L. B., U. S. Patent 2,400,255 (May 14, 1946); h t Patent 574 088 (1946). (78) Phillips Petroleum Co., “Hydrofluoric Acid Alkylation,” Char 10, 267-83 (1946). (79) Pinkston, J. T., Jr., IND. ENG.CHEM.,39, 255-8 (1947). (80) Prange, F. A., and Findlay, R. -4., Petroleum Refiner, 25, No 3 97-100 (1946). (81) Price. G. H. S.,’Metal Treatment (Brit.), 13, 208-12 (1946). (82) Priest, H. F., and Grosse, A. V., IND.ENG.CHEM..39, 279-8(1 (1947). (83) Ibid., 39, 431-3 (1947). (84) Roehl, E. J., Netal Finishing, 45, 56-9, 71 (1947). (85) Schlect, L., and Tregeser, G., Metallm’rtschaft, 19, KO.4, 6ti (1940). (86) Schlect, L. and Treyeser, G., Chem. Fabrik., 12, No. 19-20, 243 (1939). (87) Schrader, R. J. and DeHaan, A., C h a . Eng.,53, No. 11. 9f1-lnl (1946). (88) Sisco, F. T., Mining & Metallurgy, 27, 276-7 (1946). (89) SOC.Automotive Engrs., Spec. Publieation SP-22 (19461. (90) Sweeny, W. O., Product Eng., 17, No. 9, 121-6 (1946). (91) Symposium on Fluorine Chemistry, ISD. Ex;. CIIEM., 39. 236434 (1947). (92) Taylor, T. A., Proc. Inst. 111rch. Engrs., 153 (War Emergency Issue 12), 508-12 (1945). (93) Wachter, A., Treseder, R. S., and Weber, M. K.. Corrosion. 3, 406-14 (1947). (94) Wheeler, J. A., Mech. Eng.,68, 401-5 (1946). (95) Wick, Machinery, 69, 586-9 (1946). (96) Wilkinson, E. R.. Corrosion, 3, 252-62 (1947). (97) Winkleback, R. K.. Automotive a.nd A v i a t i m Inds., 95, No. h. 40-4 (1946). (98) Woldman, N. E., Materials $. Methods, 24, 1475-90 (1946; (99) Wood, E., Metal I n d . (London). 67, 435-9 1945).
PLASTICS G . M. KLINE, National Bureau of Standards, Washington, D . C .
T
HE plastics industry has emerged from World War I1 with new materials and techniques pyramided upon the already imposing prewar array. Further additions to this list can be expected when production catches up with the demand for existing types of plastics. In fact, the outlook for materials development, in this field is limitless in view of the possibilities for synthesis of new organic compounds, and their copolymerization and polycondensation into an infinite array of synthetic resins. This review summarizes recent developments in the rapidly expanding field of plastics.
quantities of it had been made during the latter period of World War I1 for military applications. Polytetrafluoroethylene, marketed as Teflon, is inert t o all types of chemicals except molten alkali metals. It does not have a true melting point but does undergo a solid phase change at 620” F. with a corresponding sharp drop in strength. It gives off small amounts of fluorinecontaining gases above 420” F. Because of its high softening temperature it can be shaped only by special techniques. Suggested applications include coaxial cable spacers, valve packing?, gaskets, and plug cocks and tubing for chemical plant equipment
POLYTETRAFLUOROETHYLENE
Availability of the polymer made from the tetrafluorine derivative of ethylene, the most recent addition to the roster of plastics, was announced during 1946 (16, 48, B I ) , although appreciable
POLYETHYLENE
The parent substance of the foregoing tetrafluorine derivative
has been made in commercial quantit,ies in this country since
