Hot corrosion and CMAS degradation of laser-glazed YSZ coating with optimum parameter

Abstract

The purpose of this research is to look into the effect of laser surface modification on the hot corrosion and hot corrosion  +  calcium–magnesium aluminosilicate (CMAS) resistance of YSZ thermal barrier coating. Metco AMDRY 997 (Ni–22Cr–10Al–Y) powder was coated as a bond coat on the AISI 304L stainless steel substrate using a high-velocity oxy-fuel spray technique. As a ceramic top layer, 204 NS YSZ (ZrO₂·8Y₂O₃) particles were plasma sprayed on the bond coat. Following that, the entire coating surface was treated with a 20-kHz pulsed CO₂ laser to increase the coatings’ surface performance. A corrosion test was carried out in a box furnace for 20 h at 1050 °C. SEM images of laser-glazed coatings revealed denser surfaces than those of air-spraying coatings. The laser-modified coating is more resistant to hot corrosion than unmodified coatings. The X-ray diffraction analysis revealed that the reaction between yttria (Y₂O₃) and V₂O₅ resulted in the formation of YVO₄ crystals as a corrosion product. According to energy dispersive spectroscopy results, laser-glazed coatings reduced molten salt diffusion from surface to bond coat. As a result, laser-glazed coatings demonstrated improved hot corrosion resistance and decreased corrosion products on the bond coat zone. After the hot corrosion test, the laser-treated composite had a 55% lower thermally grown oxide layer than untreated APS YSZ. The optimum laser parameter was used as 77.7 W laser power, 120 mm/s scanning speed, and 215 mm laser distance.