Effect of starting materials on the wear performance of NiTi-based composites

NiTi alloys have exhibited significant potential as a matrix of wear resistant composites. In this study, in order to examine the effect of starting materials on the wear performance of NiTi-based composites, both elemental Ni/Ti and prealloyed NiTi powders were used to fabricate NiTi-6 wt% nano-Al2O3 composites using hot isostatic pressing (HIP). Nanoindentation and microhardness test results indicate that the composite samples produced from the elemental Ni/Ti powders exhibited higher hardness and lower pseudoelasticity properties than those of the samples fabricated from the prealloyed NiTi powders; this is attributed to the higher amount of Ni3Ti/NiTi2 phases in the samples from the elemental powders. The wear test results also confirm the superior performance of the composite samples produced from the elemental powders. The high-resolution transmission electron microscopy studies of the wear debris demonstrate that the heavy local plastic deformation induced during the wear test appeared to inhibit the pseudoelasticity during the wear process. Hence, it can be deduced that the role of the hardness enhancement is more pronounced than that of the pseudoelasticity reduction in the wear performance of NiTi-based composite samples.