Under dry sliding wear, the evolution of oxides in severely plastic deformed(SPD) regions of metals has a great impact on the wear behaviors. To study the evolution behaviors of oxides in the SPD region, an SPD region was prefabricated on the surface of AISI 52100 steel by supersonic ?ne particle bombarding(SFPB) treatment. Dry sliding wear tests were carried out on both of the SFPB-treated and original samples.Wear volume loss of the SPBF-treated samples were compared with those of the original samples at different loads. Microstructure, element composition and oxides distribution in the SPD region were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and an electron probe microanalysis(EPMA). The results show that the evolution behaviors of the oxides in the SPD region change signi?cantly with the load. Under low loads, oxides are usually formed on the contact surface. It inhibits adhesive wear on the steel. However, under high loads, oxides are apt to distribute along the cracks in the subsurface layer. The internal oxidation along the cracks can accelerate the cracks propagation, resulting in severe delamination wear on the steel.
The physical vapor deposition method is an effective way to deposit Al_2O_3 and Er_2O_3 on 316 L stainless steel substrates acting as tritium permeation barriers in a fusion reactor. The distribution of residual thermal stress is calculated both in Al_2O_3 and Er_2O_3 coating systems with planar and rough substrates using finite element analysis. The parameters influencing the thermal stress in the sputter process are analyzed, such as coating and substrate properties, temperature and Young's modulus. This work shows that the thermal stress in Al_2O_3 and Er_2O_3 coating systems exhibit a linear relationship with substrate thickness, temperature and Young's modulus.However, this relationship is inversed with coating thickness. In addition, the rough substrate surface can increase the thermal stress in the process of coating deposition. The adhesive strength between the coating and the substrate is evaluated by the shear stress. Due to the higher compressive shear stress, the Al_2O_3 coating has a better adhesive strength with a 316 L stainless steel substrate than the Er2_O_3 coating. Furthermore, the analysis shows that it is a useful way to improve adhesive strength with increasing interface roughness.
