Parameter optimization of T800 coating fabricated by EHLA based on response surface methodology

• RSM was used to establish empirical relationships to predict clad height and Vickers hardness. The predicted values agree well with the experimental results. • The results of the ANOVA tables show that the laser power, surface speed, and overlap rate had the most significant effect on the clad height. The clad height increased with an increase in the laser power and overlap rate, whereas the surface speed had a negative effect. Simultaneously, the laser power and surface speed had the most-significant effects on Vickers hardness. The laser power had a negative effect, whereas the surface speed had a positive effect. • According to the desirability optimization results, the optimal processing parameters of laser power is 5.9 kW, surface speed is 45 m/min, carrier-gas flow rate is 18 L/min, and string overlap is 56 %. T800 coating prepared by these parameters has a clad height in range of 30–40 μm, Vickers hardness in the range of 580–600 HV, and no cracks by EHLA. This coating fabricated by EHLA can be prepared as an alternative to HCPP. Extreme high-speed laser material deposition (EHLA) is a new laser cladding technology which enable ultra-high processing efficiency. It has a higher processing efficiency of as much as 500 cm 2 /min, which is ten times of conventional laser cladding. In this study, EHLA was investigated systematically by depositing Kennametal Stellite Tribaloy 800 alloy (T800) on a 316 L stainless-steel roller. In order to obtain optimal processing parameters of T800 coatings without macroscopic cracks applied by EHLA, the effects of the input processing parameters, i.e., laser power, surface speed, carrier-gas flow rate, and string overlap (%), on the output responses (clad height and Vickers hardness) were analysed by Response surface methodology (RSM) and analysis-of-variance method. RSM was used to design an experimental matrix and quadratic regression model. The analysis-of-variance method was used to analyse and test the developed model. The results show that the predictive quadratic regression models (as shown in Formula 5 and 6) of Clad height and Vickers hardness of the coatings fabricated by EHLA obtained in this paper are accurate and reliable respectively. Combined with the models analysis, the laser power has a positive effect on the clad height of the coating, but a negative effect on the Vickers hardness, and the effect of surface speed is opposite. The last but not least, the clad height and Vickers hardness of no crack T800 coating prepared by optimal processing parameters are 35.8 μm and 602.1HV respectively.