THE ROLE OF SUBSURFACE DEFORMATION AND STRAIN LOCALIZATION ON THE SLIDING WEAR BEHAVIOR OF LAMINATED COMPOSITES

The sliding wear behaviour of laminated composites of copper and amorphous Ni78Si10B12 fabricated by diffusion bonding was investigated. Unlubricated sliding tests were performed using a block-on-ring type wear machine in order to provide a direct comparison of the wear mechanisms in the metallic glass (Ni78Si10B12) layers and polycrystalline matrix (copper) and to determine the influence of the metallic glass layers on the overall wear resistance of the composite. Wear in the copper layer was characterized by extensive plastic deformation and by the presence of subsurface cracks. These cracks originated at the shear bands within the plastic zones under the contact surfaces and caused delamination of the material adjacent to these surfaces. The wear of metallic glass layers also involved the localization of plastic deformation into shear bands. However, due to the high hardness and fracture strength of Ni78Si10B12, its wear resistance was higher than the copper matrix. Localized strain and temperature gradients generated during sliding contact led to the crystallization of amorphous layers. Metallic glass layers were effective in increasing the wear resistance of the composite by supporting the load with less deformation and thereby obstructing the damage process initiated in the copper layers.