Process Parameters Optimization of Laser Cladding for HT200 with 316L Coating Based on Response Surface Method

In order to improve the sealing surface performance of gray cast iron gas gate valves and achieve precise molding control of the cladding layer, as well as to reveal the influence of laser cladding process parameters on the morphology and structure of the cladding layer, we prepared the 316L coating on HT 200 by using Design-Expert software central composite design (CCD) based on response surface analysis. We built a regression prediction model and analyzed the ANOVA with the inspection results. With a target cladding layer width of 3.5 mm and height of 1.3 mm, the process parameters were optimized to obtain the best combination of process parameters. The microstructure, phases, and hardness variations of the cladding layer from experiments with optimal parameters were analyzed by the metallographic microscope, confocal microscope, and microhardness instrument. The experimental results indicate that laser power has a significant impact on the cladding layer width, followed by powder feed rate; scan speed has a significant impact on the cladding layer height, followed by powder feed rate. The HT200 substrate and 316L can metallurgically bond well, and the cladding layer structure consists of dendritic crystals, columnar crystals, and equiaxed crystals in sequence. The optimal process parameter combination satisfying the morphology requirements is laser power (A) of 1 993 W, scan speed (B) of 8.949 mm/s, powder feed rate (C) of 1.408 r/min, with a maximum hardness of 1564.3 HV0.5, significantly higher than the hardness of the HT200 substrate.