Renewable Cr2O3 Nanolayer on Cr(W)N Surface for Seizure

Subscriber access provided by TUFTS UNIV

Surfaces, Interfaces, and Applications

Renewable Cr2O3 Nanolayer on Cr(W)N Surface for Seizure Prevention at Elevated Temperatures Chen Zhao, Xueyuan Nie, and Jimi Tjong ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b07938 • Publication Date (Web): 09 Jul 2018 Downloaded from http://pubs.acs.org on July 16, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Renewable Cr2O3 Nanolayer on Cr(W)N Surface for Seizure Prevention at Elevated Temperatures Chen Zhao†, Xueyuan Nie*, †, Jimi Tjong‡ †

Department of Mechanical, Automotive & Materials Engineering, University of Windsor,

Windsor, Ontario N9B 3P4, Canada ‡

Powertrain Engineering Research & Development Center, Ford Motor of Canada, Windsor,

Ontario N9A 6X3, Canada KEYWORDS: Cr2O3 nanolayer; Cr(W)N coating; XPS; Adhesive wear; Seizure

ACS Paragon Plus Environment

1

ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 28

ABSTRACT: Chromium nitride coating is now the norm for improving the wear resistance of high-performance mechanical components. Even so, to prevent the seizure issue between the contacting interfaces, the prerequisites are oil or solid lubricants which would however lose the lubricating functionality at elevated temperatures due to breakdown or degradation. In this research, we utilize Cr2O3 nanolayer formed on modified Cr(W)N coating to prevent the adhesive seizure for steel-based components. X-ray photoelectron spectroscopy (XPS) analyses show that the chromium oxide can be generated at 200-400°C. At 400°C, the Cr2O3 nanolayer is in-situ formed and maintains a consistent thickness of 2.2 nm due to the oxide renewal during the heating-sliding operation. The in-situ, renewable oxide nanolayer provides a novel approach to technically unsolved seizure problem occurring on high-performance machine operated at the elevated temperatures.

1. INTRODUCTION Wear in mechanical components, together with corrosion, can cause degradation of the surfaces, eventually leading to the loss of functionality and failure of materials. The wear issue has large economic relevance, which was outlined in the Jost Report1 and addressed by Holmberg and Erdemir.2 Since wear and corrosion are surface phenomena, a coating can effectively maximize the performance with minimized costs. TiAlN-based and CrAlN-based coating systems are used for protection of cutting tools and alloy-based components;3, 4 and the alloying of Si or transition metal atoms (e.g., Ti, V, Mo, and W) could enhance the coatings’ performance further through nanocomposite structures.3-5 For the massive industrial applications, a CrN coating has been widely used for surface protection of steel-based components like gears, bearings, piston rings and stamping dies due to its low costs but still high hardness, superior wear resistance, and


2

Page 3 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


excellent corrosion resistance.6-8 However, when sliding against steels, the CrN coating will likely suffer from seizure (i.e., severe adhesive wear) under highly-stressed sliding conditions.9 Aghababaei et al., 10, 11 Steele et al.,12 and Tangpatjaroen et al.,13 have investigated the adhesive wear and other wear mechanisms. Oil lubricants and solid lubricants such as Diamond-like Carbon (DLC)6, 14 are effective in preventing seizure or adhesive wear at ambient temperatures. However, the lubricants likely degrade at elevated temperatures; and as a result, high-performance mechanical components (piston rings and hot-stamping dies at up to 400°C, for instance) may seize. Transition metal sulfides (e.g., MoS2 and WS2)15, 16 or soft metals (e.g., Ag)4 can function as solid lubricants and withstand high temperatures (e.g., 400-500°C),4 but their hardness is low so that they can be worn off easily under high sliding forces. Alternatively, oxidation films are generally able to suppress the adhesive wear issue,17 which seemingly provides an effective method to reduce the materials transfer-induced seizure (i.e., severe adhesive wear caused by material transfer and counterface adhesion).17 Although pristine Cr can form a thin surface layer of oxide, the relatively low hardness of the metallic chromium would limit its applications under high load conditions. One solution may be to deposit an oxide layer with a thickness of a few microns on top of nitride; however, the oxide layer having a micro-scaled thickness is usually brittle. Only when its thickness is a few nanometers, an oxide would show a ductile behavior.18 However, such an oxide nanolayer is obviously too thin for the durability concern under highly stressed sliding contact conditions. Therefore, renewability of the layer is critical to keep the function of adhesion prevention alive. It has been reported that the oxidation of CrN can occur between 650 and 750°C,19-22 which is unfortunately much higher than the working temperatures of hardened steel-based components.


3


Page 4 of 28

Therefore, it is desirable to design a modified CrN coating with a relatively low oxidation temperature at which the hardened steel would not be softened. It was reported that the alloying of a second transition metal with a large atomic radius, such as Mo (r=0.190nm) or W (r=0.192nm) vs. Cr (r=0.166nm), could lead to distortion of CrN crystalline lattice.23-25 It is revealed that the lattice constant of CrN increased more for the W doping than the Mo doping on the one hand.23-25 On the other hand, possible formation of W oxides can start as early as room temperature.26 Can this lattice distortion and W oxides be used as “catalysts” to promote superficial conversion of CrN to Cr2O3 for adhesion prevention? This work was to address the above concern. A Cr(W)N coating was thus prepared by cathodic arc deposition5 and its oxidation behaviors were investigated at room temperature and elevated temperatures (i.e., 200°C and 400°C) by XPS analyses.27 The influence of oxide films on seizure was investigated using a self-developed high temperature inclined sliding wear tester (Figure S1). If this experiment could verify the above concern, the adhesive wear prevention (Figure 1) can be extended to the elevated temperatures of around 400°C. Otherwise, it is still an unsolved technique problem for a typical steel-based component.

Figure 1. Seizure prevention extended to elevated temperatures by Cr2O3 nanolayer on Cr(W)N surface.


4

Page 5 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2. RESULTS AND DISCUSSION Crystalline structure analysis The XRD pattern (Figure 2) of the Cr(W)N coating shows four peaks at 37.2˚, 43.3˚, 75.5˚ and 79.6˚, which are coincident with the (111), (200), (311) and (222) planes of face-center cubic CrN (JCPDS 11-0065),28 respectively. Only one single phase could be identified; no segregation of W could be found (Figure S2). Compared with peaks of the pristine CrN,28 these peaks slightly shift to the lower angles (by 0.2-0.3˚), which indicates that the incorporation of W indeed caused the expansion of the CrN lattice. The calculated lattice constant was 0.418nm. The EPMA and XPS survey scan (Figure S3) showed that the W content was ~1.5 at.%. These values are considered in good agreement with a previous report.23 The report also found that the lattice constant increased quickly with W contents up to 5 at.%, and then the lattice constant barely increased.23 The XRD pattern also shows a slightly broadening, which could be explained by the reduced grain size5, 23 and residual stresses in the lattice5 due to the W doping.

Figure 2. XRD pattern of the Cr(W)N coating. Oxidation behaviors of W


5


Page 6 of 28

Surface oxidation of the Cr(W)N coating was carried out by high-frequency induction heating: samples 1 (2s@400°C), 2 (2h@400°C), 3 (2s@200°C), 4 (2h@200°C), 5 (no heating), and 6 (2000 cycles of heating-sliding@400°C). The samples were analyzed with XPS. The ratios of peak areas for the W 4f7/2 (WO3/WO2) and Cr 2p3/2 (Cr2O3/CrN) are summarized in Table 1. As shown in Figure 3, the W 4f spectra of samples 1, 3 and 5 did not reveal any significant difference. For all the samples four similar peaks could be found at locations of 32.7±0.2 eV, 34.6±0.2 eV, 34.9±0.2 eV and 36.8±0.2 eV, which are related to the W 4f7/2 in WO2, W 4f7/2 in WO3, W 4f5/2 in WO2 and W 4f5/2 in WO3.29, 30 No peak of metallic tungsten was found. As the temperature increased, the peak of WO3 became higher, suggesting a higher content of WO3. The heating time had an insignificant effect, as indicated by the similar peak area ratios for the samples heated for 2s and 2h. This phenomenon reveals that there might be a self-limitation in the oxidation of W below the surface due to low oxygen diffusion; and the content of WO3 would be higher in the top layer of the surface. It is noticed that sample 6 went through 2000 cycles of heating-sliding wear test which was terminated by the last cycle of sliding. The top surface (rich in WO3) was thus worn away, which explains the smaller peak area ratio of WO3/WO2 for sample 6 compared to samples 1 and 2 (Table 1).

Figure 3. W 4f spectra of (a) sample 1 (heated 2s@400°C), (b) sample 3 (heated 2s@200°C), and (c) sample 5 (no heating).


6

Page 7 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 1. Peak area ratios of samples 1 (heated 2s@400°C), 2 (heated 2h@400°C), 3 (heated 2s@200°C), 4 (heated 2h@200°C), 5 (no heating), and 6 (heating-sliding 2000 cycles@400°C). Sample 1

Sample 2

Sample 3

Sample 4

Sample 5

Sample 6

I(Cr2O3)/I(CrN)

1.72

1.76

0.026

0.027

0

0.82

I(WO3)/I(WO2)

0.551

0.587

0.482

0.485

0.326

0.462

Thickness of Cr2O3 (Å)

22.3

22.6

-

-

-

14.0

Oxidation behaviors of CrN The Cr 2p3/2 spectra of samples 1, 3, 5 and 6 are presented in Figure 4. All spectra have one similar peak located at 574.7±0.2 eV, which is consistent to Cr 2p3/2 in CrN.31,

32

However,

different from the case of unheated sample 5, the spectra of samples 1, 3 and 6 have extra five peaks located at 575.5±0.2 eV, 576.5±0.2 eV, 577.3±0.2 eV, 578.3±0.2 eV and 579.1±0.2 eV as shown in Figures 4a, 4b and 4d, which are corresponding to the splitting peaks of Cr 2p3/2 in Cr2O3.33 It is noted that the peak area of Cr2O3 was very small for the 200°C cases (i.e., samples 3 and 4), which means the validation of the peak fitting process in these cases need further clarification. On the other hand, the same peak fitting process works well for the 400°C cases, as shown in Figures 4a and 4d for samples 1 and 6. The very small Cr2O3 peaks of sample 3 however demonstrated that the oxidation of CrN barely occurred at 200°C.


7


Page 8 of 28

Figure 4. Cr 2p3/2 spectra of (a) sample 1 (heated 2s@400°C), (b) sample 3 (heated 2s@200°C), (c) sample 5 (no heating), and (d) sample 6 (heating-sliding 2000 cycles@400°C). It is also noticed that sample 6 has a smaller ratio of peak areas (Cr2O3/CrN) compared with sample 1. As mentioned before, sample 6 went through 2000 cycles of heating-sliding wear test which was terminated by the last cycle of sliding. The top surface was thus worn away, which leads to a smaller ratio of peak areas. Since oxidation is an inward diffusion process initiated at the surface, it is reasonable to assume that a single, uniform Cr2O3 nanolayer overlaid on the surface of CrN (Figure 1). Thus, we could use the overlayer mode34 to calculate its thickness:


8

Page 9 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


ࡺࡺ ࣅࡺ ࡵࡻ × + ૚൰ ࢊ = ࣅࡻ ‫ ࢔࢒ × ࣂ ܖܑܛ‬൬ ࡺࡻ ࣅࡻ ࡵࡺ where d is the thickness of the oxide film; λO and λN the photoelectron inelastic mean free paths in the Cr2O3 and CrN, respectively; θ the electron take-off angle (with respect to the sample surface, 90° in the present study); NO and NN the volume density of metal atoms in the Cr2O3 and CrN, respectively; IO and IN the areas of the Cr2O3 and CrN photoelectron peaks, respectively. λO and λN are 18Å and 17.2Å when the kinetic energy of photoelectron is 913eV (in the present work).35 Estimated densities for Cr2O3 and CrN yield a NN/NO ratio of 1.5.36 As summarized in Table 1, the ratios of peak areas IO/IN are 1.72 and 1.76 respectively for samples 1 and 2. The calculated thicknesses of the oxide on surfaces of samples 1 and 2 were 22.3Å and 22.6Å, respectively. Thus, the oxidation of CrN can occur very fast at 400°C, and an approximately 2 nm thick Cr2O3 nanolayer could be established within 2s. The thickness was barely increased after a longer time of the heating, which suggests the Cr2O3 nanolayer is thermodynamically stable at 400°C. When taking the ratios of peak areas IO/IN as 0.026 and 0.027 for samples 3 and 4, the calculated thicknesses were about 0.6Å, which is smaller than the radius of Cr (1.66 Å), and thus there is no monolayer even formed. Since the precondition of the equation is a single, uniform oxide overlayer above the CrN,34,

37

the calculations are invalid for samples 3 and 4. These

invalid calculations however suggest that although a trace amount of CrN was seemingly oxidized at 200°C, it cannot form a continuous Cr2O3 overlayer on the CrN. Milošev et al., investigated the oxidation behavior of pristine CrN by using XPS analyses and reported that the formation of a nanoscaled Cr2O3 film (with a thickness of 15Å) only occurred at 450°C and beyond.32 In this work, the thicker Cr2O3 layer formed at the reduced temperature (22Å at 400°C) indicates that the W-doping might prompt the oxidation of CrN. This synergistic


9


Page 10 of 28

effect may be due to the expansion of the CrN lattice and the existence of W oxides locally in the lattice structure which provides the path for oxygen diffusion and promotes its reaction with Cr. Influence of oxide films on materials transfer To investigate the significance of the self-renewable behavior of the Cr2O3 nanolayer on the materials transfer prevention, Sample 6 was subjected to an in-situ cyclic heating-sliding test at 400°C. Sample 1 (after heated 2s@400°C) was tested with sliding movements at room temperature for comparison. It turns out that sample 1 could barely withstand 100 cycles of the sliding, as indicated by the adhesive failure and severe materials transfer in Figure 5a. At the center of the contact area, the maximum wear track depth was larger than 5µm (Figure 5b), which means the coating was peeled off. This is due to the highest stress at the center area of the wear track. At the edge, the dark-red spots represent the materials transfer from the steel counterface, which was subsequently confirmed by the SEM image (Figure 5c) and EDX point analysis. Although the W could be oxidized at room temperature, its content (1.5 at. %) was too little to form a continuous tungsten oxide film on the surface for prevention of the materials transferring. The CrN cannot oxidize at room temperature, and thus a pre-prepared thin Cr2O3 layer could not be repaired at room temperature. As soon as the Cr2O3 nanoscaled layer was removed after a few sliding cycles, the fresh CrN, which usually has higher affinity to steel, was exposed and severe steel materials transfer occurred subsequently (Figure 6a). In other words, lubricants are still needed for room temperature applications as done in the common practices.


10

Page 11 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5. (a, d) Surface morphologies of samples 1 and 6; (b, e) 2D-profiles of samples 1 and 6, at locations marked by the red arrows; (c, f) SEM images of the selected areas of samples 1 and 6, marked by the black squares. Nevertheless, XPS analyses confirmed that the W-doping could promote the oxidation process of CrN. As a result, the formation of a Cr2O3 nanolayer at a moderate elevated temperature (i.e., 400°C) was possible. Moreover, such a nanolayer can be renewed at 400°C after it was worn off in each of the sliding cycle (Figure 6b). Accordingly, it appears that sample 6 always showed an “inert” oxide surface and ultimately an excellent resistance to materials transfer even after 2000 cycles of highly stressed sliding condition (with maximum Hertz contact stress 3.5 GPa). As illustrated in Figure 5d, the wear track of sample 6 was smoother and shallower than that of sample 1. Materials transfer and adhesive wear were greatly suppressed (Figure 5f). The maximum depth of the wear track was smaller than 2µm (Figure 5e). All these indicate that sample 6 was benefited from the heating cycles at the elevated temperature. It should be noted that the test was an accelerated test and the loading condition was so severe that the wear mode


11


Page 12 of 28

was changed to the fatigue cracking after 2000 cycles (still almost no materials transfer). In other words, there would be no adhesive seizure problem for a long-term usage of Cr(W)N at the elevated temperature; only after surface fatigue cracks start to appear, the materials transfer then occurs and generates wear debris which would subsequently lead to adhesive wear.10,11

Figure 6. Schematic illustration of (a) seizure issue occurred on fresh CrN surface, and (b) seizure prevented by the self-renewable Cr2O3 nanolayer on Cr(W)N. As mentioned previously, the experiment for sample 6 was terminated after the 2000th cycle of sliding without induction heating afterward. Therefore, the chromium oxide film was not recovered after the last cycle of sliding, which explains the divergence of sample 6 from samples 1 and 2 (Table 1). Using the overlayer mode and taking the ratio of peak areas IO/IN as 0.82, the calculated thicknesses of the Cr2O3 nanolayer was 14.0Å. Thus, the thickness-loss of the Cr2O3 nanolayer during the last (also each) sliding cycle could be estimated as 8.3Å. Thus, 2000 cycles of the heating-sliding would cause a wear track to have a depth of 1.7µm, which is well consistent with the measured depth of the wear track shown in the surface profile (Figure 5e). In summary, the CrN coating is widely used for protecting mechanical components from seizure under lubricating conditions at relatively low temperatures. To extend its application to a higher temperature region, a “convenient” strategy used in this work was to modify the CrN coating by adding large atoms into its lattice structure. At elevated temperatures around 400°C, as the highest operational temperature for a steel-based component, the added atoms activated


12

Page 13 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


the surface oxidation of CrN, and a nanoscaled continuous oxide overlayer was thus in-situ formed and renewed after each of sliding cycles. Therefore, the seizure problem can be prevented. 3. CONCLUSIONS A Cr(W)N coating with a trace amount of tungsten doping was deposited on hardened H13 steel. Only a small quantity of tungsten oxides was found in the coating which cannot prevent materials transfer-induced seizure problems. However, tungsten/tungsten oxides can stimulate the oxidation of CrN at a moderate elevated temperature. Thus, a Cr2O3 nanolayer with a thickness of 2.2 nm, which would not impair the loading bearing capacity of the coating, can be formed and keep renewed at 400°C. This renewable Cr2O3 nanolayer could effectively suppress the materials transfer and adhesive seizure when it is sliding against steels. While oils and DLC coatings have been applied on the surfaces of mechanical components to avoid the seizure issues at working temperatures lower than 300°C, this research provides a promising method of the seizure prevention that can extend the utilization of hardened steels for high-performance mechanical components to the elevated temperatures up to 400 °C. 4. Experimental section A Cr(W)N coating was deposited on hardened H13 steel using a cathodic arc deposition technique. The deposition process started from pumping the vacuum chamber down to 1.5×10-3 Pa, followed by inletting Ar and N2 as plasma and reactive gas sources, respectively. The working pressure after the gas input was controlled at 3.5×10-1 Pa. 7 disc-shaped Cr targets and 2 disc-shaped W targets were used in the vacuum chamber. The substrate bias voltage was set as 150V. The substrate temperature was maintained at 350°C during the deposition process. The thickness, hardness and reduced modulus of the coating were determined to be 5µm (Figure


13


Page 14 of 28

S2a), 22GPa, and 200GPa (Figure S2b), respectively. The content of W in the coating was ~1.5 at.%, as detected by electron probe micro analyzer (EPMA), and confirmed with the XPS survey scan (Figure S3). The structure of the Cr(W)N coating was determined by X-ray diffraction (XRD, PROTO AXRD). X-ray photoelectron spectroscopy (XPS) analyses were performed by a Kratos AXIS Nova Spectrometer using a monochromatic Al Kα source (15 mA, 14 kV). Before tests, the instrument work function was calibrated with a standard metallic gold reference sample to give binding energy (BE) of 83.95 eV for metallic Au 4f7/2. The dispersion of the spectrometer was adjusted with a standard copper reference sample to give binding energy of 932.63 eV for metallic Cu 2p3/2. The Kratos charge neutralizer system was used for all analyses with charge neutralization. XPS survey scan analyses with a pass energy of 160eV were carried out on selected areas of 300µm×700µm, and then high-resolution analyses were carried out with a pass energy of 20eV, which is corresponding to Ag 3d5/2 FWHM of 0.55 eV. Spectra were analyzed with CasaXPS software (version 2.3.14).38 Gaussian (Y%)-Lorentzian (X%), which is defined as GL (X) in CasaXPS, line shapes were used for peak fitting of the spectra. For the satellite structure of transition metal oxides, i.e., WO2, WO3 and Cr2O3 in present work, GL (30) line shapes are used for each individual component, which gives the best fitting effect. Reasonable results of the peak areas are obtained as long as the Gaussian-Lorentzian mix is in a reasonable range and applied consistently.33 For CrN core lines, asymmetry was defined in the form of LA (α, β, m), where α and β define the spread of the tail on either side of the Lorentzian component. The parameter m specifies the width of the Gaussian used to convolute the Lorentzian curve. In present work, LA (3.4, 25, 17) line shapes were used for fitting the CrN component. A standard Shirley background is used for all reference sample spectra. A Shirley type baseline with varying


14

Page 15 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


amounts of offset at the high binding energy end was used for fitting the spectra. The above processes have an associated error of ±0.1-0.2eV.33 In the present work, we adopt the uncertainty as ±0.2eV. The renewable behavior of the Cr2O3 nanolayer and its influence on material transfer were studied by cyclic heating-sliding tests. The process of the cyclic heating-sliding is illustrated in Figure 7, where in each cycle the sample was induction heated for 2s followed by the sliding wear test against a steel ball (SAE 52100, HRC 58-60, 9.5mm in diameter) with an increased load from 50N to 250N (i.e., the maximum Hertz contact stresses from 1.9 GPa to 3.4 GPa). An optical pyrometer was used to control the sample surface temperature. After the tests, the samples were unmounted and ultrasonically cleaned to remove the loose wear debris. An optical profilometer (ZeGage Plus) and scanning electron microscopy (SEM, FEI Quanta 200 FEG) were used to observe the sliding contact areas. Energy dispersive X-ray (EDX) analysis was carried out to characterize the materials transferring.

Figure 7. Schematic of cyclic heating-sliding tests.


15


Page 16 of 28

SUPPORTING INFORMATION XPS survey scan and scheme of the high-temperature inclined sliding wear tester are given in supporting information. Corresponding Author * [email protected] (X. Nie) Author Contributions The manuscript was written through contributions of all authors. All authors have approved the final version of the manuscript. ACKNOWLEDGEMENTS This research was supported by Natural Sciences and Engineering Research Council of Canada (NSERC); Auto/Steel Partnership, USA; and Ford Motor of Canada. Thanks to Dr. Mark Biesinger in Western University for XPS analyses. REFERENCES (1) Jost, H. P. Lubrication (tribology): Education and research, a report on the present position and industry's needs. Department of Education and Science, London, 1966. (2) Holmberg, K.; Erdemir, A. Influence of Tribology on Global Energy Consumption, Costs and Emissions. Friction 2017, 5, 263-284. (3) Franz, R.; Mitterer, C. Vanadium Containing Self-Adaptive Low-friction Hard Coatings for High-temperature Applications: A review. Surf. Coat. Technol. 2013, 228, 1-13. (4) Aouadi, S. M.; Gao, H.; Martini, A.; Scharf, T. W.; Muratore, C. Lubricious Oxide Coatings for Extreme Temperature Applications: A review. Surf. Coat. Technol. 2014, 257, 266-277.


16

Page 17 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(5) Chen, W. L.; Lin, Y.; Zheng, J.; Zhang, S. H.; Lin, S. Y.; Kwon, S. C. Preparation and Characterization of CrAlN/TiAlSiN Nano-multilayers by Cathodic Vacuum Arc. Surf. Coat. Technol. 2015, 265, 205-211. (6) Nie, X.; Zhang, P.; Weiner, A. M.; Cheng, Y. T. Nanoscale Wear and Machining Behavior of Nanolayer Interfaces. Nano Lett. 2005, 5, 1992-1996. (7) Wang, L.; Northwood, D. O.; Nie, X. Corrosion Properties and Contact Resistance of TiN, TiAlN, and CrN Coatings in Simulated Proton Exchange Membrane Fuel Cell Environments. J. Power Sources 2010, 195, 3814-3821. (8) Liu, C.; Bi, Q.; Matthews, A. EIS Comparison on Corrosion Performance of PVD TiN and CrN Coated Mild Steel in 0.5 N NaCl Aqueous Solution. Corros. Sci. 2001, 43, 1953-1961. (9) Su, J. F. Investigation of Metallurgical Coatings for Automotive Applications. Ph.D Thesis, University of Windsor, Windsor, Canada, 2014. (10) Aghababaei, R.; Warner, D. H.; Molinari, J. F. Critical Length Scale Controls Adhesive Wear Mechanisms. Nat. Commun. 2016, 7, 11816. (11) Aghababaei, R.; Warner, D. H.; Molinari, J. F. On the Debris-level Origins of Adhesive Wear. PNAS 2017, 114, 7935-7940. (12) Steele, A.; Davis, A.; Kim, J.; Loth, E.; Bayer, I. S. Wear Independent Similarity. ACS Appl. Mater. Interfaces 2015, 7, 12695-12701. (13) Tangpatjaroen, C.; Grierson, D.; Shannon, S.; Jakes, J. E.; Szlufarska, I. Size Dependence of Nanoscale Wear of Silicon Carbide. ACS Appl. Mater. Interfaces 2017, 9, 1929-1940. (14) Vanhulsel, A.; Velasco, F.; Jacobs, R.; Eersels, L.; Havermans, D.; Roberts, E. W.; Sherrington, I.; Anderson, M. J.; Gaillard, L. DLC Solid Lubricant Coatings on Ball Bearings for Space Applications. Tribol. Int. 2007, 40, 1186-1194.


17


Page 18 of 28

(15) Berman, D.; Narayanan, B.; Cherukara, M. J.; Sankaranarayanan, S. K. R. S.; Erdemir, A.; Zinovev, A.; Sumant, A. V. Operando Tribochemical Formation of Onion-like-carbon Leads to Macroscale Superlubricity. Nat. Commun. 2018, 9, 1164. (16) Hao, R.; Tedstone, A. A.; Lewis, D. J.; Warrens, C. P.; West, K. R.; Howard, P.; Gaemers, S.; Dillon, S. J.; O’Brien, P. Property Self-Optimization during Wear of MoS2. ACS Appl. Mater. Interfaces 2017, 9, 1953-1958. (17) Stachowiak, G. W.; Batchelor, A. W. Engineering Tribology, 3rd ed; Elsevier ButterworthHeinemann: Oxford, 2005. (18) Yang, Y.; Kushima, A.; Han, W. Z.; Xin, H. L.; Li, J. Liquid-Like, Self-Healing Aluminum Oxide during Deformation at Room Temperature. Nano Lett. 2018, 18, 2492-2497. (19) Tu, J. N.; Duh, J. G.; Tsai, S. Y. Morphology, Mechanical Properties, and Oxidation Behavior of Reactively Sputtered Cr-N films. Surf. Coat. Technol. 2000, 133-134, 181-185. (20) Mitterer, C.; Mayrhofer, P. H.; Musil, J. Thermal Stability of PVD Hard coatings. Vacuum 2003, 71, 279-284. (21) Mayrhofer, P. H.; Willmann, H.; Mitterer, C. Oxidation Kinetics of Sputtered Cr-N Hard Coatings. Surf. Coat. Technol. 2001, 146-147, 222-228. (22) Lu, F. H.; Chen, H. Y.; Hung, C. H. Degradation of CrN Films at High Temperature under Controlled Atmosphere. J. Vac. Sci. Technol. A 2003, 21, 671-675. (23) Yau, B. S.; Chu, C. W., Lin, D.; Lee, W.; Duh, J. G.; Lin, C. H. Tungsten Doped Chromium Nitride Coatings. Thin Solid Films 2008, 516, 1877-1882. (24) Kim, K. H.; Choi, E. Y.; Hong, S. G.; Park, B. G.; Yoon, J. H.; Yong, J. H. Syntheses and Mechanical Properties of Cr-Mo-N Coatings by a Hybrid Coating System. Surf. Coat. Technol. 2006, 201, 4068-4072.


18

Page 19 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(25) Zhou, L. C.; Klimashin, F. F.; Holec, D.; Mayrhofer, P. H. Structural and Mechanical Properties of Nitrogen-deficient Cubic Cr-Mo-N and Cr-W-N systems. Scripta Materialia 2016, 123, 34-37. (26) Warren, A.; Nylund, A.; Olefjord, I. Oxidation of Tungsten and Tungsten Carbide in Dry and Humid Atmospheres. Int. J. Refract. Met. Hard Mater. 1996, 14, 345-353. (27) Li, T.; Nie, X. One-Step Fast-Synthesized Foamlike Amorphous Co(OH)2 Flexible Film on Ti Foil by Plasma-Assisted Electrolytic Deposition as a Binder-Free Anode of a High-Capacity Lithium-Ion Battery. ACS Appl. Mater. Interfaces 2018, 10, 16943-16946. (28) Powder Diffraction File Card 11-0065, Joint Committee on Powder Diffraction Standards, ASTM: Philadelphia, 1996. (29) Colton, R. J.; Rabalais, J. W. Electronic Structure to Tungsten and some of its Borides, Carbides, Nitrides, and Oxides by X-ray Electron Spectroscopy. Inorg. Chem. 1976, 15, 236-238. (30) Shi, J.; Allara, D. L. Characterization of High-Temperature Reactions at the BaO/W Interface. Langmuir 1996, 12, 5099-5108. (31) Milošev, I.; Strehblow, H. H.; Navinšek, B. XPS in the Study of High-temperature Oxidation of CrN and TiN Hard Coatings. Surf. Coat. Technol. 1995, 74-75, 897-902. (32) Milošev, I.; Abels, J. M.; Strehblow, H. H.; Navinšek, B.; Metikoš-Hukovič, M. High Temperature Oxidation of Thin CrN Coatings Deposited on Steel. J. Vac. Sci. Technol. A 1996, 14, 2527-2534. (33) Biesinger, M. C.; Payne, B. P.; Grosvenor, A. P.; Lau, L. W. M.; Gerson, A. R.; Smart, R. St. C. Resolving Surface Chemical States in XPS Analysis of First Row Transition Metals, Oxides and Hydroxides: Cr, Mn, Fe, Co and Ni. Appl. Surf. Sci. 2011, 257, 2717-2730.


19


Page 20 of 28

(34) Strohmeier, B. R. An ESCA Method for Determining the Oxide Thickness on Aluminum Alloys. Surf. Interface Anal. 1990, 15, 51-56. (35) Johnson, S. G. NIST Electron Inelastic-Mean-Free-Path Database, NIST: Gaithersburg, 2010. (36) Hodgman, C. D. Handbook of chemistry and physics, Lippincott Williams & Wilkins: Philadelphia, 1951. (37) Carlson, T. A. Basic assumptions and recent developments in quantitative XPS. Surf. Interface Anal. 1982, 4, 125-134. (38) Fairley, N. http://www.casaxps.com, ©Casa software Ltd, 2005.


20

Page 21 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


TOC


21



Page 22 of 28

Page 23 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60





Page 24 of 28

Page 25 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60





Page 26 of 28

Page 27 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60





Page 28 of 28

Renewable Cr2O3 Nanolayer on Cr(W)N Surface for Seizure

Recommend Documents