High-temperature tribological performance of direct laser deposited Stellite alloy claddings on DIN 1.2714 die steel

Abstract

Direct laser deposition of Co-based alloys, specifically Stellite 6 and ERCOCR-B, was employed to enhance the tribological properties of hot-forging die steel – DIN 1.2714. The microstructure of the resultant claddings exhibited a refined microstructure consisting of an γ-Co matrix interspersed with hard phases, such as M₇C₃, M₂₃C₆, WC, and W₂C, predominantly located at the grain boundaries. Microhardness analysis revealed that the Stellite 6 cladding achieved a maximum hardness of 472 VHN, whereas ERCOCR-B achieved 539 VHN. The tribological performance of the claddings was analysed using a ball-on-disc tribometer at varying temperatures – ambient temperature, 450°C, and 550°C. Both claddings significantly outperformed the base material, with the improvement attributed to the existence of hard carbide phases. Notably, ERCOCR-B demonstrated superior wear resistance, reducing wear volume by 97.2% at ambient temperature, 90.8% at 450°C, and 62.5% at 550°C. Stellite 6 claddings exhibited 59.6% at ambient temperature, 79% at 450°C, and 48.5% at 550°C lower volume loss than substrate. The observed wear mechanisms included adhesive, abrasive, and oxidative interactions, with their extent varying with temperature and coating type.