Homogenizing porous 60NiTi parts under open atmosphere conditions

What is it about?

A typical homogenizing treatment for 60NiTi consists of solutionizing the parts to above the solvus temperature of ~1050°C (in a furnace with vacuum or inert gas atmosphere) and then quenching the parts in a quenchant. This procedure solves the Ni3Ti and Ni3Ti2 phases in B2 NiTi and results in formation of homogeneous biocompatible parts. However, vacuum furnaces with the possibility of drop-quenching the specimen after solutionizing treatment are not always available due to practical difficulties. In addition, backfilling the furnaces with inert argon gas, if not unavailable, is very expensive. This research investigates the effects of conducting sloutionizing treatment under an open atmosphere condition on the microstructure and mechanical properties of 60NiTi parts.

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Why is it important?

It was found that this procedure produces a hard integral ceramic layer, a complex mixture of nickel and titanium oxide compounds, on the surface and around the pores of 60NiTi parts. Results showed that this heat treatment procedure causes the embrittlement of the parts due to an increase in oxide content. However, the produced ceramic surface can also enhance the resistance to corrosion, which is beneficial from a biocompatibility point of view.