The warm powder compaction process is simulated by the finite element analysis software which is MSC/MARC. The thermal mechanically coupled analysis method is applied based on the updated Lagrangian Method to study the influence of different velocities ratio of die and punch υdie/υup-punch on the properties of green under different frictional condition. The results indicate that for cylindrical powder metallurgic products, different velocity ratios have great influence on the distribution of relative density and equivalent stress. The frictional force can be converted to the favorable force through adjusting the velocity ratio, and this method can obtain higher uniform distribution of relative density and stress of green.

In order to investigate the effect of Cr content on the microstructures and oxidation wear properties of high-boron high-speed steel (HBHSS), so as to explore oxidation wear resistant materials (e.g., hot rollers), a scanning electron microscope, an X-ray diffractometer, an electron probe X-ray microanalysis and an oxidation wear test at elevated temperatures were employed to investigate worn surfaces and worn layers. The results showed that the addition of Cr resulted in the transformation of martensite into ferrite and pearlite, while the size of the grid morphology of borides in HBHSSs was refined. After oxidation wear, oxide scales were formed and the high-temperature oxidation wear resistance of HBHSSs was gradually improved with increased additions of Cr. Meanwhile, an interaction between temperature and load in HBHSSs during oxidation wear occurred, and the temperature had more influence on the oxidation wear properties of HBHSSs. SEM observations indicated that a uniform and compact oxide film of HBHSSs in the worn surface at elevated temperatures was generated on the worn surface, and the addition of Cr also reduced the thickness of oxides and inhibited the spallation of worn layers, which was attributed to improvements in microhardness and oxidation resistance of the matrix in HBHSSs. A synergistic effect of temperature and load in HBHSSs with various Cr additions may dominate the oxidation wear process and the formation and spallation of oxide films.

The formed transfer film on the counterpart surface and tribological properties of PTFE composites filled with Al2O3 or SiO2 were investigated in this paper. The results indicated that under the same friction conditions, the friction coefficients of SiO2/PTFE and Al2O3/PTFE are very close to each other, but the wear resistance of SiO2/PTFE is superior to that of Al2O3/PTFE. According to the measured data, the micro-hardness and elastic modulus of the transfer film for SiO2/PTFE are much better than those of Al2O3/PTFE. In addition, the interfacial adhesion strength between the transfer film of SiO2/PTFE and the counterface is higher. It can be proved that the mechanical properties of transfer films for PTFE composites vary with different fillers and the friction transfer film with better adhesion strength and mechanical property is useful to improve the tribological properties of the composite.

The friction and wear behaviors of PTFE composites filled with irregular or spherical copper powders were experimentally investigated. The effects of shape, content and size of the copper powders on the tribological properties of the PTFE composites were discussed. The results showed that the friction coefficients of the PTFE composites filled with irregular copper powders are higher than that of pure PTFE. While the friction coefficients of the PTFE composites filled with spherical copper powders were almost always lower than that of pure PTFE. Both irregular and spherical copper powders can effectively decrease the wear of the composites. The wear of the composites filled with spherical copper powders will gradually decrease with the increase of the content of copper. But the effect of the content of irregular copper powder on the wear of the composites was not so obvious. The friction coefficients and wear depths of the composites increase with the decrease of the Cu size. The increase amplitudes in friction coefficients and wear depths of the spherical Cu filled composites are smaller than those of the irregular Cu filled composites.

Copper-based bearing material containing Bi was prepared by running powder metallurgy process, the influence of the content of Bi on the tribological performance of copper-based bearing materials was inspected and Bi’s impact on frictional wear performance of copper-based bearing materials was studied by a MM-200 frictional wear tester. The research shows that, Bi, with a lower melting point, tends to melt and separate out, in friction process which may reduce shear strength of the friction pair surface and improve the performance of antifriction and adhesiveness resistance. When Bi content gets higher to produce more brittle phases, which will fall off directly from the matrix, the antifriction and antiwear of friction pair will weaken.