Abrasive wear behaviour of Fe, Co and Ni based metallic glasses

Metallic glasses are a different category of materials that are characterized by their amorphous structure and metallic bonds. Owing to their disordered structure, metallic glasses possess several unique properties that make them attractive for tribological applications. This paper deals with an in depth investigation into the two-body abrasive wear behaviour of several compositions of Fe, Co and Ni based metallic glasses while rubbing against metallographic grade SiC abrasive papers. Identical studies have also been carried out on crystalline cold-rolled AISI 304 stainless steel for comparison. Two-body abrasive wear results indicate that wear characteristics of different metallic glasses are marginally superior or similar to that of stainless steel. The wear in Ni based metallic glass MBF 35 is significantly higher than that in stainless steel. This is inspite of the fact that metallic glasses are considerably harder than stainless steel. Scratch indentation and acoustic emission studies (AE) were carried out with a view to understanding the mechanisms of occurrence of two-body abrasive wear in metallic glasses. Scratched surfaces of metallic glasses indicated the presence of arc-like features that in some cases extend well beyond the scratched groove edges. In the case of Ni based metallic glass MBF 35, cracking on the surface was clearly visible. In stainless steel, the grooves formed were neatly cut out and were free from the arc-like features. During scratch tests on metallic glasses, AE signals were obtained but no AE signals were generated during scratch tests on steel. Presence of arc-like features on scratched surfaces in metallic glasses are tensile micro-cracks formed due to brittle fracture owing to their poor ductility in tension. These results revealed that the abrasive wear of metallic glasses is not commensurate to their high hardness and occurrence of micro-cracking results in their poor abrasive wear resistance.