Influence of laser cladding parameters on distortion, thermal history and melt pool behaviour in multi-layer deposition of stellite 6: In-situ measurement

Abstract

Laser cladding is a surface coating technique used to produce high wear and corrosion resistance coatings. The residual stresses and distortion developed during cladding effects the clad mechanical properties, dimensional accuracy and its performance. In this present study, the substrate distortion and thermal history of Stellite 6 were monitored online during mult-ilayer deposition, using Laser Displacement Sensors (LDS) and non-contact Pyrometers. In depth analysis has been carried to investigate the effect of process parameters on distortion and temperature. The results show that, the deflection increases with increase in laser power and decrease in scan speed. The deflection measured was 18–20 % higher when the scanning speed is reduced from 20 mm/s to 12 mm/s and around 30 % more deflection when the laser power is increased to 3400 W from 2400 W. Whereas, the second layer compared to single layer deposition has shown decreased deflection which is due to the low thermal gradient along the thickness. The thermal history of the melt pool shows that the increase in Linear Heat Input (LHI) increases the melt pool life span, thereby inducing more substrate deflection. The results also reflect the formation of strong metallurgical bond and hard carbides in all the samples. The study also provided an optimum set of process parameters that induces minimum distortion in multi-layer cladding of Stellite 6.