Mechanical properties and deposition mechanism of cold-sprayed CoNiCrAlY/YSZ cermet

Abstract

The properties of agglomerated and sintered powders of the cermet of yttria-stabilized zirconia (YSZ)/CoNiCrAlY and coatings thereof were investigated. Three multimodal cermet powders were prepared with different compositions (75% CoNiCrAlY:25% YSZ; 50% CoNiCrAlY:50% YSZ; and 25% CoNiCrAlY:75% YSZ) for deposition by a cold-spraying process. Each of the cermet powders was successfully deposited onto a bond-coated substrate by the cold-spray process with low kinetic energy. Each feedstock powder ensured a homogeneous distribution of YSZ powders in the coating layer. The microstructural characterization and phase analysis of the feedstock powders and the as-sprayed coatings were obtained by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). In the XRD and EDX results, the YSZ content in the coating increased with the increase of YSZ content in the powder blend. Against conventional expectations, the deposition efficiency and hardness of the as-sprayed coatings were improved by low gas pressure. In particular, the as-sprayed coatings with more than 50 mass% YSZ showed decreased cracks in the coating layer. To understand these results, the cermet particles were coated onto Al substrates by cold-spraying. Then, the particles were cut open to observe the bonded cross-sectional surface by focused ion beam (FIB) analysis.