An investigation of the tribological behavior of HF-based bulk metallic glass and crystalline alloys

The use of bulk metallic glasses (BMGs) as advanced materials for many applications is attractive, due to their improved mechanical performance over their crystalline counterparts: typically providing higher strength and hardness. Hafnium-based alloys of two similar compositions were prepared by arc melting and suction casting to produce 6-mm-diameter cast rods of an amorphous alloy and a crystalline one. The selected compositions were Hf48Cu29Ni10Al13 (amorphous) and Hf58Cu20Ni16Ti6 (crystalline), as confirmed by X-ray diffraction. The hardness of the amorphous alloy was higher than that of the crystalline one. A detailed study of their tribological behavior was carried out, using a pin-on-disc wear tester, with tungsten carbide counterface balls. There were no statistically significant differences in friction coefficient or wear-rates between the two materials tested. Adherence of material from the tested alloy to the ball, and vice versa, were detected. No changes to the crystallinity of the bulk samples were induced by the wear process, as determined by X-ray diffraction. However, amorphous debris were obtained from both samples, indicating the possibility of local vitrification of particles detached from the crystalline alloy and confirming thermal stability of the amorphous alloy.