Influence of deposition parameters on segregation-induced strain in Ni–Cr–B–Si hardfaced coating

Ni–Cr–B–Si alloys are used to hardface stainless steel components in industry, including fast breeder reactors, to prevent galling. Segregation-induced microscopic strain in Ni–Cr–B–Si coatings can compromise microstructural integrity, yet the effect of deposition parameters on this strain remains underexplored. In this study, coatings were deposited on 316 L (N) using Plasma Transferred Arc Welding (PTAW) at two currents: 120 A and 150 A. The coating with 14 weight % of Fe (made at 120 A) exhibited predominantly coarse, rod-shaped precipitates dominant in CrB, pronounced elemental segregation (Si, Fe, and P) at the precipitate–matrix interfaces, and higher microscopic strain, with a maximum Kernel Average Misorientation (KAM) of ∼4°. In contrast, the coating with Fe weight % of 20 (made at 150 A), exhibited a reduction in coarse precipitates and the development of a finer, near-eutectic fish-bone Cr5B3 phase dominant structure, resulting in a lower maximum KAM of ∼1.8°. Characterization techniques employed included SEM, EDS, OES, EBSD, XRD, and Thermo-Calc simulation. The results indicate that dilution of the coating, influenced by deposition current, affects strain distribution by reducing primary boride precipitation and the associated local elemental concentration gradient developed during solidification. Hence, adjusting deposition parameters alters the segregation induced strain in Ni–Cr–B–Si coatings.