Effect of heat treatment on the microstructure and property of cold-sprayed nanostructured FeAl/Al2O3 intermetallic composite coating

It is difficult to deposit dense intermetallic compound coatings by cold spraying directly using compound feedstock powders due to their intrinsic low temperature brittleness. A method to prepare intermetallic compound coatings in-situ employing cold spraying was developed using a metastable alloy powder assisted with post heat treatment. In this study, a nanostructured Fe(Al)/Al2O3 composite alloy coating was prepared by cold spraying of ball-milled powder. The cold-sprayed Fe(Al)/Al2O3 Composite alloy coating was evolved in-situ to FeAl/Al2O3 intermetallic composite coating through a post heat treatment. The effect of heat treatment on the phase formation, microstructure and microhardness of cold-sprayed Fe(Al)/Al2O3 composite coating was investigated. The results showed that annealing at a temperature of 600 degrees C results in the complete transformation of the Fe(Al) solid solution to a FeAl intermetallic compound. Annealing temperature significantly influenced the microstructure and microhardness of the cold-sprayed FeAl/Al2O3 coating. On raising the temperature to over 950 degrees C, diffusion occurred not only in the coating but also at the interface between the coating and substrate. The microhardness of the FeAl/Al2O3 coating was maintained at about 600HV(0.1) at an annealing temperature below 500 degrees C, and gradually decreased to 400HV(0.1) at 1100 degrees C. (C) 2008 Elsevier Ltd. All rights reserved.