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

Abstract

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 cm2/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.