Synthesis and characterization of nano-structured NiAl intermetallic compound coating

Abstract

The stoichiometric NiAl exhibits attractive properties in terms of high melting point (1911K), high thermal conductivity, oxidation resistance and low density (5.9kg/m³). However, it has been limited to apply the material for industrial fields because of its extreme brittleness at ambient temperature range. It is considered that the refinement of grain size to nano meter level seems to be a promising way to overcome the above mentioned problem because the enhancement of hardness and strength can be expected by nano-structure, according to Hall-Petch law. In the present study, synthesis of nano-structured NiAl coating was carried out by using MA (mechanical alloying) process and HVOF (high velocity Oxy-fuel) spraying. In addition, effect of nano-structure to the mechanical properties of NiAl coating was also investigated. It was observed that the coating obtained by the process used was composed of both nano-structuered NiAl and Ni phase. However, mechanical properties of the coating were not affected so severely by the grain size of sprayed powders prepared, with the difference between approximately 20nm and 200nm.