Laser fabrication of porous surface layer on NiTi shape memory alloy

Porous NiTi shape memory alloys provide enhanced osteointegration by facilitating tissue ingrowth and transport of body fluid to the implant. To retain the excellent thermomechanical properties of bulk NiTi and to improve its biocompatibility, a porous surface layer was fabricated on bulk NiTi samples using laser surface engineering techniques. A powder mixture of NiTi and TiH2 was laser surface alloyed on the SMA. The macrostructure and microstructure of the modified surface layer were studied. A porous layer of a few hundred micrometers thick was formed, composed of NiTi, Ti2Ni, TiNi3 and TiN. The pores in the layer exhibited an inter-connected morphology in 3D. The Ni content was reduced from 49.2 at.% in the substrate to 12.5 at.% near the surface of the modified layer.