Influencing Factors and Process Optimization of Al-25si Coating Prepared by Inner-Hole Supersonic Atmospheric Plasma Spraying

Abstract

For inner-hole parts, the main positions bearing load are their inner walls, which are prone to strain, wear, corrosion and other damages during use. Aluminum-silicon (Al-Si) coating (Al-25Si) with excellent properties can be prepared through inner-hole supersonic atmospheric plasma spraying (SAPS) technology to provide reliable protection for inner-hole parts. In this paper, a study was conducted to find out how spray gas parameters, spray electrical parameters, and spray distances influence the temperature and velocity of flying particles during the process of preparing Al-25Si coatings through inner-hole SAPS. Meanwhile, the coating preparation process was also optimized in this study. Through analysis and experimental verification, the optimal process parameters for preparing the coatings are as follows: The total gas flow is 115 L/min, the hydrogen (H2) content is 7.5%, and the spray voltage, spray current, and spray distance remain at 86 V, 430 A, and 90 mm. Under these spray parameters, the particle temperature and flight velocity are 2,698.65°C and 473.9 m/s, respectively, while the porosity and microhardness of the coating are 0.79 ± 0.56% and 267.09 ± 14.85 HV 0.2, respectively.

Keywords: Supersonic plasma spraying of inner hole, High silicon aluminum coating, Particle flight characteristics, process optimization