Parametric optimization in co-axial laser powder deposition of cobalt-base alloys on DIN 1.2714 die steel

Abstract

In this work, cobalt-based powders (Stellite 6 and Stellite 12) were deposited on the hot forging die steel (DIN 1.2714) by direct laser deposition using a 2 kW Yb-fiber laser. Single tracks were developed by varying process parameters—powder mass flow rate (25–35 g/min), laser power (800–1100 W), and scan speed (400–800 mm/min). Further, the influence of these process parameters on clad geometry and dilution rate was studied. Optimization of parameters was carried out using grey analysis, and the results were analyzed based on analysis of variance (ANOVA). It was observed that the optimal parameters for Stellite 6 cladding are a powder mass flow rate of 25 g/min, laser power of 1100 W, and a scan speed of 400 mm/min. In contrast, the optimal parameters for Stellite 12 are a powder mass flow rate of 35 g/min, laser power of 1100 W, and a scan speed of 800 mm/min. In addition, a correlation between input and output parameters was established using regression analysis. The micrographs of the single-track cladding developed under optimal parametric conditions consist of fine cellular structure at the clad-surface interface followed by course cellular dendrites and fine equiaxed grains at the surface of the cladding. Stellite 12 cladding exhibits higher hardness (545 ± 10 HV0.3) than Stellite 6 cladding (470 ± 10 HV0.3) due to the formation of more refined grains.