Baoliang Zhu

Effects of lubricants on friction and wear of Ti(CN)1045 steel sliding pairs

Abstract The friction and wear properties of Ti(CN) 1045 steel rubbing pairs were investigated under dry and lubricated conditions by using a pin-on-disk tribometer. The selected speed range was 0.8 to 3.2 m/s and the load range was 58.8 to 235.2 N. Distilled water and a mineral oil (no additives) were used for lubrication, respectively. The wear of Ti(CN) ceramic under dry conditions was caused mainly by adhesion between the rubbing surfaces and the microfracture of Ti(CN). With the load and speed increasing, the adhesion and diffusion between rubbing surfaces increased and resulted in wear increasement of Ti(CN). Because of the brittleness of ceramics, the microfracture wear of Ti(CN) increased rapidly when the load was raised to some high values. The lubricating and cooling effects of the lubricants could improve the frict on and wear. Compared with water, oil was much better in improving the tribological properties. The analysis results obtained from XPS and AES examinations showed that ferrous oxide was produced on the wear scars, which could reduce the adhesion between the rubbing surfaces to some extent. The lubricating effects of the oil under boundary lubrication conditions were attributed to the formation of carbon films on the rubbing surfaces.

The computer simulation of the temperature distribution on the surface of ceramic cutting tools

Abstract The temperature distributions on the surface of Si 3 N 4 and Ti(CN) ceramic cutting tools for turning different metallic materials were calculated and plotted using computer simulation based on a mathematic model of heat sources. The results showed that the temperature on the rake face of the ceramic cutting tools for turning 18-8 stainless steel was much higher than that for turning 1045 plain carbon steel due to the much lower thermal conductivity of the former, the temperature increased with increasing cutting speed. This observation is important in explaining the wear resistance and wear mechanisms of the two ceramic cutting tools. The computed temperature distributions on the surface of the ceramic cutting tools were checked by measurement with a thermal video system (TVS), and showed good agreement.

Tribological properties of TiC-based ceramic/high speed steel pairs at high temperatures

Abstract The tribological properties of three TiC-based ceramics — HM1, HM2 and HM3 — against high speed steel were investigated by using a pin-on-disk tribometer at 25 °C and 600 °C. The results of the tests indicated that the friction coefficient and wear rate of HM2 were the lowest among the three ceramics. Its friction coefficient was 0.19, and its wear rate was 1.14 × 10 −14 m 3 /N.m. The examinations of wear scars for ceramics by means of scanning electron microscope (SEM), X-ray diffractometer (XRD) and electron probe analyser indicated that the composition and structure of oxide films formed on the sliding tracks of the ceramics exhibit an important effect on the high temperature self-lubricating behaviour. This investigation also proved that Mo can improve the tribological properties of ceramics, while WC shows a negative effect on them. The different wear mechanisms of HM1 and HM2 were also discussed in this study.

Wear simulation of Si3N4 cutting tool material on a pin-on-disc tester

Abstract Si 3 N 4 -based ceramic cutting tools are used nowadays for machining cast iron, nickel-based alloys, etc. Austenitic stainless steel AISI 321 is one of the most difficult to cut materials. In order to investigate the wear behaviour of Si 3 N 4 ceramic when cutting the stainless steel, wear tests are carried out on a pin-on-disc tribometer, which can simulate a realistic cutting process. The selected load range is from 58.8 N to 235.2 N, the speed range is from 0.8 m/s to 3.2 m/s. The test results show that the wear of Si 3 N 4 ceramic increases with both load and speed and the wear of the ceramic is mainly caused by adhesion between the rubbing surfaces. Scanning electron microscope (SEM), electron probe microanalyser (EPMA) and energy dispersive X-ray analyser (EDXS) were used for examinations of the worn surfaces. The wear mechanisms of Si 3 N 4 ceramic sliding against the stainless steel were discussed in detail.

Metal-ion implantation effects on nano-hardness and tribological properties of Nylon6

Abstract The technique of metal-ion implantation was employed for improving surface hardness and tribological properties of Nylon6. The samples of Nylon6 were implanted with the ions of Al, Ti, Fe and Ni to four fluences of 2×1015 ions cm−2, 1×1016 ions cm−2, 5×1016 ions cm−2 or 1×1017 ions cm−2. The pristine and implanted samples were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), electron spin resonance (ESR), nano-hardness indentation and wear testing. Nano-hardness and wear-resistance of Nylon6 was improved significantly by metal-ion implantation. In particular, 1×1016 ions cm−2 Al implantation showed the highest hardness of 3.34 GPa, the largest improvement by a factor of 5.4, and the smallest wear volume. The mechanisms underlying the improved nano-hardness and tribological properties are also addressed.

Tribological properties of ion-implanted polyphenylene oxide (PPO)

The technique of ion implantation was employed for improving surface hardness and wear resistance of polyphenylene oxide (PPO). The samples of PPO were implanted separately with Al, Ti and Fe ions to three doses of 2 x 10 15 , 1 x 10 16 and 1 x 10 17 ions/cm 2 . Wear tests showed that wear-resistance of PPO was improved significantly and friction coefficient was reduced. The 1 x 10 16 ions/cm 2 Ti ion implantation produced the largest improvement in tribological properties, and wear-resistance of 1 x 10 16 ions/cm 2 Ti-implanted PPO was improved over 270 times and friction coefficient was reduced by 40%. Nano-hardness increased from 0.369 GPa for the plain PPO to 1.433 GPa for 1 x 10 16 ions/cm 2 Ti-implanted PPO. TRIM96 (transport of ions in mater, version 1996) calculation revealed that ionization energy loss and energy loss difference between ionization and vacancies of Ti were more than those of Al and Fe beneath 50 nm ion implantation range, which were related to the largest improvement of surface properties for Ti ion implantation. IR-spectra of 1 x 10 16 ions/cm 2 Ti-implanted PPO indicated that the surface of samples was moisture-retentive and formed the carbonyl group. GXRD analysis showed that the crystal distance was reduced after Ti ion implantation.

Mechanical properties of ion-implanted polycarbonate

Abstract The technique of ion implantation was employed for improving surface hardness and wear resistance of polycarbonate (PC). The samples of PC were implanted separately with C, Al, Ti, Fe and Ni ions to four doses of 2×10 15 ions cm −2 , 1×10 16 ions cm −2 , 5×10 16 ions cm −2 or 1×10 17 ions cm −2 . Wear tests showed that the wear-resistance of PC was improved significantly and the friction coefficient was reduced after ion treatment, 2×10 15 ions cm −2 C ion implantation produced the largest improvement in wear-resistance by a factor of 19 times and the friction coefficient was reduced by 20%. The nano-hardness increased from 0.283 GPa for the pristine PC to 0.712 GPa for 2×10 15 ions cm −2 C-implanted PC and 1.032 GPa for 1×10 16 ions cm −2 Ni-implanted PC. TRIM96 calculation revealed that ionization energy loss, vacancy energy loss and the difference in the energy loss for ionization and vacancies of Ni near the surface were more than those of the four other ions, and this was related to the largest improvement of surface hardness for Ni ion implantation. IR spectra of 2×10 15 ions cm −2 C-implanted PC indicated that the surface of samples was moisture-retentive and formed a new carbonyl group.

Tribological characteristics of Si3N4 ceramic sliding on stainless steel

Abstract Austenitic stainless steel AISI 321 is one of the most difficult to cut materials. In order to investigate the wear behavior of Si3N4 ceramic when cutting stainless steel, wear tests were carried out using a pin-on-disk tribometer which could simulate a real cutting process. Test results show that the wear of Si3N4 ceramic is caused mainly by adhesion between the rubbing surfaces; the wear increases with load and speed. When oil is used for lubrication, the friction coefficient of the sliding pairs and the wear rate of the ceramic are reduced. Scanning electron microscopy, electron probe microanalysis, and energy-dispersive X-ray analysis were used for examination of the worn surfaces. The wear mechanisms of Si3N4 ceramic sliding against stainless steel are discussed in detail.

A study on friction and wear characteristics of substitute chromium brush plating layers under lubrication

Abstract The chromium plating layer shows excellent wear resistance under lubrication at low speed and light load. However, its wear resistance is not very good at high speed and heavy load. The newly developed substitute chromium brush plating layer behaves satisfactorily under both sets of conditions. Friction and wear tests were conducted and average and flash temperatures of substitute chromium plating layer were calculated. The microstructures of plating layer before and after the wear process were analysed by SEM, AES and XPS. The mechanism of its excellent wear resistance at high speed and heavy load is described.

The tribological performance of Ni/MoS2 composite brush plating layer in vacuum

Abstract The friction and wear behavior and microstructure of an Ni/MoS 2 composite plating layer with high MoS 2 content and sufficient thickness produced by a brush plating method were studied. Experiments were conducted using a ‘pin-on-disc’ testing machine in vacuum with a pressure of approximately (6–9) × 10 −4 Pa. The plating layer was produced on the surface of the disc. The experimental results show that the friction coefficient can only reach a lower stable value when the MoS 2 content is more than 31.6% in volume, and the minimum friction coefficient of 0.014 can be obtained at 78% MoS 2 content. In order to reveal the mechanism for the excellent solid lubrication properties of Ni/MoS 2 plating layers, detailed analyses were conducted of the microstructure and orientation of grains by transmission electron microscopy. The codeposition process of both nickel and MoS 2 phases is also discussed.