Optimization of Plasma Spraying Parameters with Respect to Shear Adhesion Strength of Cr3C2-NiCr Coating on 16Mn Steel

The adhesion strength of the thermally sprayed coatings plays a decisive role in the service life of coated parts, especially those working in high temperature environments. Besides factors relevant to material properties, the parameters in the spraying process significantly affect the adhesion strength of the coatings. This paper presents the result of optimizing 3 parameters of atmospheric plasma spraying (APS) including plasma current intensity, powder feed rate and stand-off distance to the shear adhesion strength of the Cr3C2-30%NiCr coating on the 16Mn steel achieved the best. The experiments are carried out based on Central Composite Design with 20 trials. Analysis of variance (ANOVA) and genetic algorithm (GA) were used to optimize and evaluate the influences of 3 spraying parameters on the shear adhesion strength of coating and base steel. A quadratic polynomial model is also developed to predict the shear adhesion strength value based on the parameters. The results reveal that all three parameters have significance to shear adhesion, in which the current intensity is the most influential parameter, followed by the stand-off distance and powder feed rate, respectively. The optimization results showed that with the current of 577.5A, powder feed rate of 31.5g/min and stand-off distance of 167mm, the shear adhesion achieved the best value of about 49.81 MPa. In addition, the verified experimental results have an error of about 1.06%, compared with the optimal value.