In-flight formation and characterization of nickel aluminide powders in a dc thermal plasma jet

Abstract

The strength of some intermetallics increases with temperature instead of exhibiting a decrease: thus, they are ideally suited for high temperature applications. The formation of intermetallic compound during the spray process leads to metallurgical bonding due to the high exothermicity of the formation reaction. In this paper formation of nickel aluminide in a thermal plasma jet from ball-milled nickel–aluminium powders is reported. Commercially available nickel and aluminium powders were mixed in the appropriate amount and injected in to a thermal plasma jet produced by an atmospheric plasma torch. During in flight the formation of nickel aluminide takes place in plasma jet. Powders were collected at two different collection distances (40 and 80 cm) for three power levels (10, 15 and 20 kW), different plasma gas flow rates (15 and 20 lpm) and different powder feed rate (7 and 14 g/min). The powders are characterized using SEM, optical micrograph, TG/DTA and XRD analysis. The effect of plasma parameters on the formation have been studied and reported. The formation is better at higher power levels, low powder feed rate, low plasma gas flow rate and longer collection distances.