Influence of Si on Microstructures and High-Temperature Properties of MCrAlY Type Coating

The CoCrAlSiY alloy coating with Si mass concentrations of 0%, 2% and 5% was prepared. The effect of Si element on the structure and properties of the alloy powder and coating was analyzed. In addition, the function of Si element on the high temperature performance of the coating was also discussed. The results show that the Si element is mainly distributed in the β phase, whose volume content and distribution have a great influence on the high temperature performance of the coatings. Furthermore, the Si element promotes the change from internal oxidation to external oxidation of the alloy and the formation of the protective oxide film. However, the much higher Si content results in a higher PBR (Pilling-Bed worth ratio) value of the oxide film, and increases the oxide film stress, which is not beneficial to the improvement of the coating thermal shock resistance at high temperatures.