Remanufacturing oriented statistical optimization and performance analysis of laser cladding Ni60 coating on 316L piston rods

In order to explore the remanufacturing of 316L piston rods, theoretical and experimental researches on laser cladding the Ni60 alloy on 316L stainless steel are conducted. A multiobjective optimization procedure is proposed to achieve appropriate process parameters based on the experimental results and the response surface method. The regression prediction models are built up to obtain the nonlinear relations between the main process parameters, as well as coating geometric dimensions and forming qualities. The laser power, scanning speed, powder feeding rate, and overlap rate are set as the input factors, and coating’s width, height, dilution rate, and hardness are set as the target responses. Through statistical analysis, the influences of the process parameters and their coupling effects on the geometric dimension and forming quality of Ni60 coatings are also studied. Then, process parameter optimization is conducted using the multiresponse desirability function method to laser cladding a given coating, and a verification experiment is carried out. Furthermore, the microstructure and mechanical performance of the Ni60 coating are investigated. The results show that there exists a dense metallurgical bonding between the substrate and the coating, and the microstructure of the coating is mainly composed of an austenite phase, a FeNi3 phase, and a (Cr, Fe)7C3 phase. The microhardness of the Ni60 coating is about three times that of 316L stainless steel, and its wear rate is significantly lower than that of 316L stainless steel. Finally, based on the optimized process parameters, repairing of the worn surface of a 316L piston rod is successfully realized.