Enhanced wear resistance and new insight into microstructure evolution of in-situ (Ti,Nb)C reinforced 316 L stainless steel matrix prepared via laser cladding

Abstract

An MC (M: Ti,Nb) carbide-reinforced 316 L coating was synthesized in-situ via laser cladding. A strong relationship between the (Ti,Nb)C content and the microstructure and tribological properties of the resulting components was established. This relationship helped explain the influence of the (Ti,Nb)C content on the phase evolution, microstructure characteristics, and exothermic reaction behavior. It was found that the size and morphology of in-situ generated (Ti,Nb)C particles changed as the carbide content increased. When the MC carbide content increased from 2.5 wt% to 10 wt%, the morphology of in-situ generated (Ti,Nb)C evolved from irregular geometry particles, to spherical particles, and finally into near-regular geometry. When the carbide content reached 15 wt%, the (Ti,Nb)C particles displayed an equilibrium octahedral structure. The calculated formation enthalpy of MC carbides showed that the reaction enthalpy increased with the MC carbide content, which affected the dynamic temperature of the molten pool and eventually led to carbides with different crystal morphologies and sizes. Room-temperature dry sliding friction and wear tests showed that the submicron (Ti,Nb)C carbide reinforced (carbide content: 5 wt%) coating and 1.5 μm regular octahedral particle-reinforced coating (carbide content: 20 wt%) exhibited a lower friction coefficient and wear volume loss. Understanding the morphological evolution mechanism of (Ti,Nb)C and its corresponding tribological behavior will enable the development of guidelines to obtain (Ti,Nb)C/316 L metal matrix composite coatings produced by laser cladding.