PREPARATION AND MECHANICAL PROPERTIES OF NANOSTRUCTURED CRYOMILLED NiCrAlY ALLOY FABRICATED BY SPARK PLASMA SINTERING

NiCrAlY coatings are widely used on turbine blades and vanes for protection against high temperature oxidation and corrosion. Nanostructured cryomilled NiCrAlY alloy samples were fabricated by spark plasma sintering (SPS) to provide bulk samples for in-depth characterization without the microstructural complexities that are generated in thermal sprayed coatings. Heat treatment at selected times and temperatures was also carried out. Through microhardness testing, scanning electron microscopy (SEM) and Energy-Dispersive X-ray analysis (EDAX), the mechanical properties, microstructure and phase composition were investigated. The results indicate that there was a strengthening effect in the cryomilled alloy, compared to the conventional alloy, because of refinement in the microstructure and the presence of nanostructural features. After heat treatment, the microhardness of the samples decreased, due to further changes in the microstructure.