AISI 440C Steel Substrates Research Articles

The effect of temperature on water desorption and oxide formation in MoS2 coatings and its impact on tribological properties

Molybdenum disulfide (MoS2) is used extensively in aerospace applications, where liquid lubricants are not suitable. MoS2 has excellent tribological properties in vacuum, however, further research is required to fully understand the mechanisms taking place when exposed to varying temperatures in ambient atmosphere due to storage and on-ground testing. MoS2 coatings were deposited on AISI 440C steel substrates, friction and wear tests were conducted at increasing temperatures, up to 75 °C, determining the effect of temperature on wear mechanisms in air. It was found that the detected surface oxides do not impact tribological properties in MoS2 at temperatures around 75 °C. The water molecules at room temperature hinder the alignment of MoS2 layers leaving some active edge sites exposed to contacting surfaces, leading to high friction and wear. Desorption of water molecules promote parallel alignment of layers, reducing shear strength, friction and wear.

Influence of deposition temperature and pressure on microstructure and tribological properties of arc ion plated Ag films

The films deposited at low temperature (LT-films) have increasingly attracted theoretical and technical interests since such films exhibit obvious difference in structure and performances compared to those deposited at room temperature. Studies on the tribological properties of LT-films are rarely reported in available literatures. In this paper, the structure, morphology and tribological properties of Ag films, deposited at LT (166 K) under various Ar pressures on AISI 440C steel substrates by arc ion plating (AIP), are studied by X-ray diffraction (XRD), atomic force microscopy (AFM) and a vacuum ball-on-disk tribometer, and compared with the Ag films deposited at RT (300 K). XRD results show that (200) preferred orientation of the films is promoted at LT and low Ar pressure. The Crystallite sizes are 70 nm–80 nm for LT-Ag films deposited at 0.2 Pa and 0.8 Pa and larger than 100 nm for LT-Ag films deposited at 0.4 Pa and 0.6 Pa, while they are 55 nm–60 nm for RT-Ag films deposited at 0.2 Pa–0.6 Pa and 37 nm for RT-Ag films deposited at 0.8 Pa. The surfaces of LT-Ag films are fibre-like at 0.6 Pa and 0.8 Pa, terrace-like at 0.4 Pa, and sphere-like at 0.2 Pa, while the surfaces of RT-Ag films are composed of sphere-like grains separated by voids. Wear tests reveal that, due to the compact microstructure LT-Ag films have better wear resistances than RT-Ag film. These results indicate that the microstructure and wear resistance of Ag films deposited by AIP can be improved by low temperature deposition.

Comparative study of microstructure and tribological behavior of TiC/a‐C:H and a‐C:H coatings in a sand‐dust environment

AbstractTiC/a‐C:H and a‐C:H nanocomposite coatings were prepared on AISI 440C steel substrates using magnetron sputtering process. A comparative study was made on their composition and microstructure by Raman spectroscopy and high‐resolution transmission electron microscopy (HRTEM). The tribological properties of two types of carbon‐based coatings were investigated by pin‐on‐disc tribometer under the sand‐dust conditions concerning the influence of applied load, amount of sand and sand particle sizes. The results show that these carbon‐based coatings exhibited high tribological performance with low friction coefficient and wear rate under the sand‐dust environments. However, the TiC/a‐C:H coatings exhibit relatively higher fluctuant friction coefficient as well as higher wear rate in comparison with the a‐C:H coatings under sand‐dust environments. The formation of nanocrystalline hard TiC phase distributed in amorphous carbon matrix decreased the residual stress but significantly increased the hardness and Young's modulus of TiC/a‐C:H coatings, and consequently caused a relatively higher abrasive and fatigue wear loss under the sand‐dust conditions. Copyright © 2010 John Wiley & Sons, Ltd.

Ultra-High Tribological Performance of Magnetron Sputtered a-C:H Films in Sand-Dust Environment

The hydrogenated amorphous carbon (a-C:H) films were prepared on AISI 440C steel substrates using a RF magnetron sputtering graphite target in the CH4 and Ar mixture atmosphere. The friction and wear behavior of a-C:H films were comparatively investigated by pin-on-disc tester under dry sliding and simulated sand-dust wear conditions. In addition, the effects of applied load, amount of sand and sand particle sizes on the tribological performance of a-C:H films were systemically studied. Results show that a-C:H films exhibited ultra-high tribological performance with low friction coefficient and ultra-low wear rate under sand-dust environments. It is very interesting to observe that the friction coefficient of a-C:H film under sand-dust conditions was relatively lower when compared with dry sliding condition, and the wear rate under sand-dust conditions kept at the same order of magnitude (×10−19 m3/N m) with the increase of applied load and particle size as a comparison with the dry sliding condition. Based on the formation of “ridge” layer (composite transfer layer), a transfer layer-hardening composite model was established to explain the anti-wear mechanisms and friction-reducing capacity of a-C:H solid lubrication films under sand-dust conditions.

Structural, morphological, wettability and thermal resistance properties of hydro-oleophobic thin films prepared by a wet chemical process

The structural properties of fluorine containing polymer compounds make them highly attractive materials for hydro-oleophobic applications. However, most of these exhibit low surface energy and poor adhesion on the substrates. In the present investigation, crack free, smooth and uniform thin films of poly[4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole]-co-tetrafluoroethylene (TFD-co-TFE) with good adhesion have been deposited by wet chemical spin-coating technique on polished AISI 440C steel substrates. The as-deposited films (xerogel films) have been subjected to annealing for 1h at different temperatures ranging from 100 to 500°C in an argon atmosphere. The size growth of the nano-hemispheres increased from 8nm for xerogel film to 28nm for film annealed at 400°C. It was found that as the annealing temperature increased from 100 to 400°C, nano-hemisphere-like structures were formed, which in turn have shown increase in the water contact angle from 122° to 147° and oil (peanut) contact angle from 85° to 96°. No change in the water contact angle (122°) has been observed when the films deposited at room temperature were heated in air from 30 to 80°C as well as exposed to steam for 8 days for 8h/day indicating thermal stability of the film.

The effect of deposition parameters and Ti content on structural and wear properties of MoS 2[sbnd]Ti coatings

MoS 2 Ti composite films were deposited on silicon wafers and AISI 440C steel substrates with different target currents and working pressures by closed field unbalanced magnetron sputtering (CFUBMS). The composition of MoS 2 Ti films was determined by EDS. Crystallographic properties of MoS 2 Ti composite films produced were investigated by XRD and the friction and wear properties were determined by means of pin-on-disk tribotester. The effect of deposition parameters and Ti content on crystallographic orientation and friction coefficient and wear rate was examined.

Structure and high-temperature tribological behavior of Ti–Si–C nanocomposite thin films

Multiphase, thin Ti–Si–C films have been deposited from elemental targets (Ti, Si) by pulsed, double source, reactive magnetron sputtering in argon–acetylene atmosphere on steel substrates. Optical emission plasma spectroscopy was used to control deposition conditions. The composition of the coatings was determined by electron microprobe working in energy/wave dispersive spectroscopy mode, based on reference samples analyzed by Rutherford Backscattering Spectroscopy. X-ray diffraction indicates the coexistence of TiCx and traces of Ti5Si3Cx, TiSi2 and SiC phases in dependence on nominal composition of the coatings. Low-temperature (400 °C) deposits transform from nanocrystalline to amorphous with increasing silicon content. Microhardness of 2-μm-thick films on AISI 440C steel substrates have been tested by means of Vickers indentation and ranges from 7.5 to 16 GPa. Tribological behavior during dry friction in air of normal humidity was studied in the wide temperature range (20 to 450 °C) using ball-on-disc configuration. The lowest, room temperature friction (μ<0.3) was observed for samples containing less than 15 at.% of silicon. These films, consisting of TiCx nanocrystallites, encapsulated in amorphous SiC/aC:H matrix, show also the best high-temperature properties. Results are discussed in terms of chemical and phase composition of studied films.

Study of tribological performance of ECR–CVD diamond-like carbon coatings on steel substrates: Part 2. The analysis of wear mechanism

This paper describes the tribological performance of diamond-like carbon (DLC) coatings deposited on AISI 440C steel substrates by electron cyclotron resonance chemical vapor deposition (ECR–CVD) process. A variety of analytic techniques were used to characterize the coatings, such as Raman spectroscopy, atomic force microscopy (AFM) and nano-indentation. The sliding wear and friction experiments were carried out by the conventional ball-on-disk tribometry against 100Cr6 steel counterbody at various normal loads (1–10 N) and sliding speeds (2–15 cm/s). All the wear tests were conducted under dry sliding condition in ambient air for a total rotation cycle of 1 × 10 5 (sliding distance ∼2.2 km). Surfaces of the coatings and the steel balls were examined before and after the sliding wear tests. The DLC coatings that had been tested all showed relatively low values of friction coefficient, in the range of 0.1–0.2 at a steady-state stage, and low specific wear rates (on the order of 10 −8 mm 3/Nm). It was found that higher normal loads or sliding speeds reduced the wear rates of the coatings. Plastic deformation became more evident on the coating surface during the sliding wear test at higher contact stresses. The friction-induced transformation of the coating surface into a graphite-like phase was revealed by micro-Raman analysis, and the flash temperature of the contact asperities was estimated. It was suggested that the structural transformation taking place within the wear tracks was mainly due to the formation of compact wear debris layer rather than the frictional heating effect. On the other hand, an adherent transfer layer (tribolayer) was formed on the counterface, which was closely related to the steady-state friction during sliding and the wear mechanisms. Fundamental knowledge combined with the present tribological study led to the conclusion that adhesive wear along with abrasion was probably the dominant wear mechanism for the DLC/steel sliding systems. Additionally, fatigue processes might also be involved in the wear of the coatings.

Study of tribological performance of ECR–CVD diamond-like carbon coatings on steel substrates: Part 1. The effect of processing parameters and operating conditions

Diamond-like carbon (DLC) coatings were prepared on AISI 440C steel substrates at room temperature by electron cyclotron resonance chemical vapor deposition (ECR–CVD) process in C 2H 2/Ar plasma. Using the designed Ti/TiN/TiCN/TiC interfacial transition layers, relatively thick DLC coatings (1–2 μm) were successfully prepared on the steel substrates. The friction and wear performance of the DLC coatings was evaluated by ball-on-disk tribometry using a steel counterbody at various normal loads (1–10 N) and sliding speeds (2–15 cm/s). By optimizing the deposition parameters such as negative bias voltage, DLC coatings with hardness up to 30 GPa and friction coefficients lower than 0.15 against the 100Cr6 steel ball could be obtained. The friction coefficient was maintained for 100,000 cycles (∼2.2 km) of dry sliding in ambient environments. In addition, the specific wear rates of the coatings were found to be extremely low (∼10 −8 mm 3/Nm); at the same time, the ball wear rates were one order of magnitude lower. The influences of the processing parameters and the sliding conditions were determined, and the frictional behavior of the coatings was discussed. It has been found that higher normal loads or sliding speeds reduced the wear rates of the coatings. Therefore, it is feasible to prepare hard and highly adherent DLC coatings with low friction coefficient and low wear rate on engineering steel substrates by the ECR–CVD process. The excellent tribological performance of DLC coatings enables their industrial applications as wear-resistant solid lubricants on sliding parts.

Mechanical and tribological properties of amorphous carbon films deposited on implanted steel substrates

Hydrogen-free amorphous carbon (a-C) films were deposited using unbalanced magnetron sputtering technique from graphite targets on AISI 440C steel substrates implanted with (1) carbon (C), (2) titanium (Ti), and (3) titanium followed by carbon (Ti+C), respectively. After deposition, the adhesion strength of the films was examined by scratch test and Rockwell-C indentation test. The tribological performance of the films was evaluated by a typical ball-on-disk tribometer and a reciprocating wear tester. A dynamic impact tester was also carried out to study the fatigue strength of the films. In order to study the effect of the pre-treatment of steel substrates by means of ion implantation on the actual performance of a-C films, the implanted substrates were investigated by using X-ray photoelectron spectroscopy and nano-indentation, from which the composition depth profile as well as the hardness ( H) and elastic modulus ( E) depth profiles could be accurately obtained. As a result, due to higher contents of carbide bonds appeared at the outmost surface of the C and Ti+C implanted substrates, a critical load over 65 N was obtained, indicating good scratch resistance of the films. The combination of high interfacial strength and high plastic deformation resistance ( H 3/ E 2) of the Ti+C implanted substrates led to a higher load-carrying capacity and longer duration lifetime in the sliding wear test. In the dynamic impact test, the good adhesion strength and high toughness of C and Ti+C implanted substrates improved the impact resistance of the films.

Structural, Mechanical and Tribological Properties of TiN and CrN Films Deposited by Reactive Pulsed Laser Deposition

ABSTRACTNitride thin films have potential applications in different areas of silicon device technology, namely as diffusion barrier in metallization schemes, rectifying and ohmic contacts, and gate electrodes in field effect transistors. In the present investigation, TiN and CrN films have been deposited by reactive pulsed laser deposition technique using Ti and Cr targets at 10mTorr background pressure of N2. Si (100) and AISI 440C steel substrates were used for the present study. Films were deposited at different temperatures in the range of 200°C to 600°C. The deposited films exhibited densely packed grain, with smooth and uniform structures. X-ray Photoelectron Spectroscopy (XPS) analysis of the films showed and 50% Ti and 40% of N in TiN films, 45% of Cr and 45% of N in CrN films deposited on Si (111), with the balance mostly oxygen, indicating near stoichiometric composition of the deposited nitride thin films. Hardness of the films changed from 22 GPa at 200°C to 30 GPa at 600°C for TiN, whereas for CrN we obtained 26 GPa at 200°C to 31 GPa at 600°C. The residual stress in the films showed a change from compressive stress at 200°C to tensile stress at 600°C in both the cases. Friction coefficient of the films were measured by pin-on-disk technique for all films, up to the tested limit of 10, 000 cycles at 1 N load and found to be very high (≥ 1) in both cases.

Optimisation of carbon implantation pre-treatments on the adhesion strength of amorphous carbon coatings on AISI 440C steel substrates

The effect of carbon ion implantation pre-treatment conditions (implantation energy and substrate etched depth) on the adhesion strength of amorphous carbon coatings deposited onto hardened AISI 440C steel substrates was investigated. Based on the scratch test and the X-ray photoelectron spectroscopy analysis, the most influential factor on the adhesion strength was found to be the carbon concentration on the outmost surface of the implanted steel substrates. A carbon concentration of 20–30 at.% led to the highest carbide concentration and thus the highest adhesion strength between the coatings and the substrates. By optimising the implantation energy and the etched depth to expose the highest carbide bonds on the steel substrates, well-adherent carbon coatings of different thickness (0.5–2.0 μm) could be obtained. The carbon coatings possessed a high scratch resistance with a critical load over 70 N even at a coating thickness of 2.3 μm. In addition, the coatings also exhibited a good tribological performance in the ball-on-disk wear test with friction coefficients below 0.1, which was maintained constantly over 1×10 6 rotation cycles (a sliding distance of 18.8 km) of unlubricated sliding against a WC–6%Co ball.

Investigation of Structural and Mechanical Properties of UV and Microwave-Irradiated Al2O3 / ZrO2 Multilayers by Sol-Gel Coating

ABSTRACTThin film multilayers of Al2O3 / ZrO2 have been deposited on quartz and AISI 440C steel substrates at room temperature by sol-gel dip coating technique followed by annealing at different temperatures ranging from 200°C to 800°C for 5h. Prior to annealing the deposited films have been exposed 10 min to ultraviolet radiation (248 nm wavelength) and microwave (2.45 MHz at 800 W power) respectively. Unlike conventional annealing methods, microwave heating is generally quite faster, simpler, and very energy efficient. The lower temperature and shorter time with microwave irradiation might be ascribed to the activating and facilitating effect of microwave on solid phase diffusion. X-ray diffraction (XRD) and scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analyser techniques have been employed to characterize structural, morphological and elemental composition of the thin films. Adhesion strength failure measurements on films have shown critical loads up to 35 N. Nanohardness indentation tests of the films exposed to microwave have shown hardness of 10 GPa with elastic modulus of 85 GPa compared to the annealed films hardness of 4.5 GPa with elastic modulus 57 GPa.

Mechanical and tribological properties of diamond-like carbon films prepared on steel by ECR-CVD process

Diamond-like carbon (DLC) films were prepared on AISI 440C steel substrates at room temperature by the electron cyclotron resonance chemical vapor deposition (ECR-CVD) process in C 2H 2/Ar plasma under different conditions. In order to prevent the inter-diffusion of carbon and improve the adhesion strength of DLC films, functionally gradient Ti/TiN/TiCN/TiC supporting underlayers were deposited on the steel substrates in advance. Using the designed interfacial transition layers, relatively thick DLC films (1–2 μm) were successfully prepared on the steel substrates without delamination. By optimizing the deposition parameters, DLC films with hardness up to 28 GPa and friction coefficients lower than 0.15 against the 100Cr6 steel ball were obtained. In addition, the specific wear rates of the films were found to be extremely low (∼10 −17 m 3/Nm). The friction-induced graphitization mechanism of DLC was confirmed by micro-Raman analysis.

Friction and wear performance of ion-beam-deposited diamond-like carbon films on steel substrates

In this study, we investigated the friction and wear performance of ion-beam-deposited diamond-like carbon (DLC) films (1.5 μm thick) on AISI 440C steel substrates. Furthermore, we performed a series of long-duration wear tests under 5, 10 and 20 N loads to assess the load-bearing capacity and durability limits of these films under each load. Tests were performed on a ball-on-disk machine in open air at room temperature, about 22 ± 1 °C, and humidity, about 30% ± 5%. For the test conditions explored, we found that (1) the steady state friction coefficients of pairs without a DLC film were in the range 0.7–0.9 and the average wear rates of 440C balls (9.55 mm in diameter) sliding against uncoated 440C disks were on the order of 10 −5 mm 3 N −1 m −1, depending on contact load; (2) DLC films reduced the steady state friction coefficients of test pairs by factors of 6–8, and the wear rates of pins by factors of 500–2000; (3) the wear of disks coated with a DLC film was virtually unmeasurable whereas the wear of uncoated disks was quite substantial; (4) the DLC films were able to endure the range of loads, 5–20 N, without delamination, and to last over 1 000 000 cycles before wearing out. During long-duration wear tests, the friction coefficients were initially on the order of 0.15, but decreased to some low values of 0.05–0.07 after sliding for 15–25 km, depending on the load, and remained low until wearing out. This low friction regime was correlated with the formation of a carbon-rich transfer film on the wear scar of 440C balls. Microlaser Raman spectroscopy and scanning electron microscopy were used to examine the structure and chemistry of worn surfaces and to elucidate the wear- and friction-reducing mechanisms of the DLC film.