What is Hot Isostatic Pressing of Coatings

       Coating hot isostatic pressing (HIP for short) is to place the sprayed coating sample in a hot isostatic pressing equipment, in an Ar atmosphere, after raising the temperature to a higher temperature (usually about 1200 ℃), The sample is subjected to a higher pressure (generally between 50 and 200 MPa), kept for several hours, and then cooled to room temperature. Taking the zirconia thermal barrier coating as an example, after the HIP treatment, the bonding bottom layer and the ZrO2 layer become more dense, and the cracks in the ZrO2 coating are reduced; the untransformed tetragonal phase with higher Y2O3 content in the coating will occur A certain degree of recrystallization will form a fine equiaxed grain structure. Due to the sintering effect, a certain metallurgical bond will be formed between the layers or between the deformed particles, which will improve the bonding strength of the coating and cause the fracture mode of the coating to change. A thin Al2O3 layer is formed on the interface between the bonding bottom layer and the ZrO2 surface layer, which can improve the oxidation resistance of the thermal barrier coating. At the interface between the bonding bottom layer and the substrate, in the bottom layer Significant interdiffusion of Ni and Fe in the matrix occurred. The changes in coating structure brought about by HIP treatment are all beneficial to improve the performance of thermal barrier coatings.