Wen Yue

Understanding integrated effects of humidity and interfacial transfer film formation on tribological behaviors of sintered polycrystalline diamond

Polycrystalline diamond (PCD) used in down-hole tool applications is ideally suited for harsh environments such as drilling at circulation break and poor lubrication, in which the water molecules of physical and chemical adsorption can severely affect the tribochemistry effect across the cutting interface. Here, tribological behaviors of PCD are studied in a controlled humid atmosphere (5–50% RH). The friction coefficient is ∼0.04 under 5% RH conditions, which is significantly increased to ∼0.11 under 50% conditions. The run-in period and wear rate of PCD decrease with increasing RH levels during the tribotest. Such an ultra-low friction coefficient regime is explained to coincide with the formation of efficient carbonaceous transfer films in the run-in periods through ex situ, micro-laser Raman spectroscopy and Atomic Force Microscope (AFM) measurements.

Thermal stability of ultrahard polycrystalline diamond composite materials

Thermal stability of the ultrahard polycrystalline diamond (UHPCD) composite material developed by the reinforcement of the polycrystalline diamond (PCD) with chemical vapor deposition (CVD) diamond has been investigated in a flow of argon at 1200°C. The indentation, Raman spectra and wear test have been performed to compare hardness, C-C structure and wear resistance of untreated and thermal treated UHPCD. It has been shown that the hardness of CVD diamond in UHPCD attains 133 ± 7 GPa after high pressure and high temperature (HP-HT), while after thermal treatment the hardness decreases to 109 ± 3 GPa, and the wear resistance of the thermal treated UHPCD decreases from 0.17 to 0.6 mg/km. The narrowing of full width at half maximum (FWHM) and shift of Raman peak to lower frequencies of CVD diamond in thermal treated UHPCD imply a decrease of crystal structural defects and compressive stresses, which results in a drop of the hardness of CVD diamond in a thermal treated UHPCD. The higher wear rate of thermal treated UHPCD is due to the lower hardness.

Preparation and Characterization of Sulfurized Tungsten Doped Non-hydrogenated Diamond-Like Carbon Films

A tungsten doped non-hydrogenated diamond-like carbon (W-DLC) film was prepared by ion beam assisted deposition, and then W-DLC film was sulfurized by low temperature ion sulfurization. The structural analyses were performed on the scanning electron microscope, optical profilometer, Raman spectroscope and transmission electron microscope equipped with energy dispersive spectroscope. The results showed that the low temperature ion sulfurization treatment increase ID/IG ratio from 3.5 to 4.0 and 3.4 to 3.8 for sulfurized DLC and W-DLC films, respectively. The microstructures of sulfurized DLC film changed from amorphous to nanocrystalline/amorphous structure after low temperature ion sulfuration. The sulfurized W-DLC film was composed of nanocrystallites β-WC1−X, WS2 and FeS, which uniformly dispersed in the amorphous DLC matrix.

Tribological behaviors of W/Mo films under lubrication of zinc dithiophosphates – understanding their roles in tribochemical reactions

Abstract Surface treatment is an effective factor in determining tribological performance, particularly for the condition of oil lubrication. Tungsten (W), molybdenum (Mo), and tungsten–molybdenum alloy (W-Mo) films were prepared on AISI 316L steel by ion beam–assisted deposition (IBAD). Tribological tests of the three modified surfaces using zinc dithiophosphate (ZDDP) lubrication were conducted on an SRV-2 tester and the tribochemical properties of different surfaces were analyzed. Surface analysis tools such as scanning electron microscopy (SEM), X-ray diffractometry (XRD), nano-indentation, and X-ray photoelectron spectroscopy (XPS) were used to study the microstructure, hardness, and chemical characteristics of the tribofilms generated on the worn surfaces. The results showed that these three modified films had better antiwear and antifriction properties than the AISI 316L substrate using both poly-α-olefin (PAO) and ZDDP-containing PAO lubrication, and they had different tribochemical reactions with ZDDP that determined their tribological behaviors.

Tribological behaviour of textured titanium under abrasive wear

ABSTRACT In order to improve the tribological behaviour of titanium used in aerospace exploration. Dimple textures were prepared on a commercial pure titanium grade 2 (TA2) surface by laser surface texturing. Tribological behaviour of the textured TA2 was investigated under two kinds of simulated lunar soil particles in dry sliding contact. The tribological mechanisms were analysed using NanoMap-D 3D surface profilometer, scanning electron microscope and energy-dispersive spectroscopy. An orthogonal analysis was used to study the influence of dimple parameters on anti-friction and anti-wear performances. The result showed that the textured titanium surface exhibited a better anti-friction and anti-wear performance under the small particle wearing condition compared with that under the large particle. The dimple density had a remarkable effect on both the anti-friction and anti-wear performances under small particle wear, while it became weaker under large particle wear. The dimple depth had almost no effect on the tribological behaviour.

Tribological Behavior of the 316L Stainless Steel with Heterogeneous Lamella Structure

In this paper, the tribological behavior of 316L stainless steel with heterogeneous lamella structure (HLS), prepared through 85% cold rolling technology and subsequent annealing treatment (750 °C, 10 min), were conducted on a ball-on-disc tribometer under different normal loads in dry ambient air conditions. The morphologies, structures, and compositions of the raw and worn surfaces were analyzed by 3D surface profilometer, XRD, SEM, EDS and TEM. Based on this, the results showed that the HLS 316L stainless steel samples exhibited lower and more steady friction coefficients than coarse-grained samples, especially under higher loads, which can be attributed to the existence of numerous oxidative particles across sliding interfaces. However, the wear resistance of HLS 316L stainless steel sample was a little weakened compared to that of the coarse-grained sample under a normal load of 5 N. When the load increases up to 15 N, an obviously decreased wear resistance was found for the HLS of the 316L stainless steel sample, which was 50% lower than that of coarse-grained sample. This can be ascribed to the more severe oxidative and abrasive wear performance of HLS 316L stainless steel sample under dry sliding conditions.