SiC-YAG Coating Microstructure Optimization Through Powder Feedstock Manufacturing Process Control

Abstract

A silicon carbide/yttrium aluminum garnet (SiC/YAG) composite powder feedstock material developed and patented by NTNU (Norway) in 2012 has been used to produce industrial SiC thermal spray coatings since 2014. This powder is the first of its kind in the thermal spray industry. The commercial powder is produced by the agglomerated and sintered route (A&S), making it suitable mostly for High-Velocity Oxygen Fuel, but it can also be produced by the sintered and crushed (S&C) manufacturing route for Atmospheric Plasma Spray (APS). In this work, a S&C route is proposed using jaw crusher, hammer mill, and ball milling techniques. The resulting powders were then deposited using APS and were compared with the reference A&S powder. The chemistry and the microstructure of the powders and coatings were characterized using electron microscopy, x-ray diffraction, and Vickers microhardness. The S&C powders showed a density higher than the A&S powder and a blocky morphology. The S&C powders had almost no internal porosity and kept the same chemical composition as the A&S version. The coatings obtained with the S&C powders outperformed the A&S coatings, having less porosity, higher hardness, and no secondary phases.