Liu Yuanfu

Microstructure and Wear Resistance of Plasma Jet Clad Ti5Si3/NiTi Composite Coating

A wear resistant Ti5Si3/NiTi composite coating was fabricated on a substrate of a titanium alloy by plasma jet cladding using Ni-Ti-Si elemental powder blends. The microstructure, microhardness and wear resistance of the coating were evaluated. The result shows that the plasma jet clad composite coating has a rapidly solidified microstructure consisting of blocky primary Ti5Si3 and the inter-blocky Ti5Si3/NiTi eutectics and is metallurgically bonded to the titanium substrate. The composite coating has high hardness and excellent wear resistance under the dry-sliding-wear test condition.

(Ti,Al)N Film On Normalized T8 Carbon Tool Steel Prepared By Pulsed High Energy Density Plasma Technique

Under optimized operating parameters, a hard and wear resistant ( Ti,Al)N film is prepared on a normalized T8 carbon tool steel substrate by using pulsed high energy density plasma technique. Microstructure and composition of the film are analysed by x-ray diffraction, x-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning electron microscopy. Hardness profile and tribological properties of the film are tested with nano-indenter and ring-on-ring wear tester, respectively. The tested results show that the microstructure of the film is dense and uniform and is mainly composed of ( Ti,Al)N and AlN hard phases. A wide transition interface exists between the film and the normalized T8 carbon tool steel substrate. Thickness of the film is about 1000 nm and mean hardness value of the film is about 26GPa. Under dry sliding wear test conditions, relative wear resistance of the ( Ti,Al)N film is approximately 9 times higher than that of the hardened T8 carbon tool steel reference sample. Meanwhile, the ( Ti,Al)N film has low and stable friction coefficient compared with the hardened T8 carbon tool steel reference sample.

Microstructure and Properties of Cr3Si/γ-Fe Composite Coating Prepared by Plasma Transferred Arc Cladding Technique

Under optimized operating parameters, a wear and corrosion resistant Cr3Si/γ-Fe composite coating is fabricated on a normalized 0.45% carbon steel substrate by using the plasma transferred arc (PTA) cladding technique with Fe-Cr-Si elemental powder blend as the precursor material. Microstructure, microhardness, dry-sliding wear resistance and electrochemical corrosion characteristic of the coating are evaluated. Test results show that the composite coating is mainly composed of primary Cr3Si dendrites and the interdendritic supersaturated iron-base solid solution γ-Fe. Between the Cr3Si/γ-Fe composite coating and the normalized 0.45% carbon steel substrate, there is a narrow metallurgical bonding zone. The Cr3Si/γ-Fe composite coating exhibits high microhardness, excellent wear and corrosion resistance under test conditions.

Shadow Effect and Its Revisal in Grid-Enhanced Plasma Source with Ion Implantation Method

The implanting voltage, gas pressure and the grid electrode radius are the key parameters influencing the surface grid shadow effect that has been observed in our grid-enhanced plasma source ion implantation experiment. To reduce the shadow effect and obtain a corresponding better implantation uniformity of sample surfaces, we need to use lower implanting voltage, higher gas pressure and smaller grid radius. Furthermore, we apply an axial magnetic field to increase the plasma density inside the tube and to mix the plasma outside the grid, so that the shadow effect of sample surfaces can be weakened.

Influence of ion species ratio on grid-enhanced plasma source ion implantation

Grid-enhanced plasma source ion implantation (GEPSII) is a newly proposed technique to modify the inner-surface properties of a cylindrical bore. In this paper, a two-ion fluid model describing nitrogen molecular ions N2+ and atomic ions N+ is used to investigate the ion sheath dynamics between the grid electrode and the inner surface of a cylindrical bore during the GEPSII process, which is an extension of our previous calculations in which only N2+ was considered. Calculations are concentrated on the results of ion dose and impact energy on the target for different ion species ratios in the core plasma. The calculated results show that more atomic ions N+ in the core plasma can raise the ion impact energy and reduce the ion dose on the target.