Nitride reinforced tial formed by reactive low pressure plasma spraying

Abstract

Low pressure plasma spraying (LPPS) with reactive gas, referred to as RLPPS, is one of feasible in-situ fabrication processes for intermetallic-matrix composites (IMCs). This chapter discusses that nitride dispersed TiAl based IMC layers are successfully produced from pre-alloyed TiAl powder by RLPPS process using nitrogen as a powder carrier gas. Ternary nitride precipitates Ti2AlN formed at the inter-layer boundaries of the splayed TiAl layers. The RLPPS TiAl layer formed with an appropriate spray distance of 400mm had the maximum hardness of 709Hv at room temperature, which was significantly higher than hardness of a non-reinforced LPPS TiAl layer formed with argon carrier gas. Although the hardness values of RLPPS TiAl layers dropped to approximately 450Hv after the high-temperature exposure at 1273 Kelvin for 24 hours, the hardness value is higher by approximately 100 Hv than that of the LPPS TiAl layer. This mainly results from the nitride precipitation hardening.