Refining effect of nitrogen on M₇C₃ carbides in hypereutectic Fe–25Cr–4C–0.5Ti–0.5Nb hardface coatings

Abstract

Hypereutectic Fe–Cr–C–Ti–Nb coatings with N additives were developed by surface-hardening welding (hardfacing). The experimental results showed that the primary M7C3 carbides were refined by the N additives in the coatings. Based on the micro-morphologies of M7C3 and (Ti,Nb)(C,N), the (Ti,Nb)(C,N) was present inside the primary M7C3 carbides, and they were tightly combined. The mismatch between the (010) crystal plane of M7C3 and the (110) crystal plane of (Ti,Nb)(C,N) was 6.15%, which indicated that (Ti,Nb)(C,N) was moderately effective as a heterogeneous nucleus of M7C3 carbides. Therefore, the preferentially precipitated (Ti,Nb)(C,N) in the Fe–Cr–C–Ti–Nb coating was the heterogeneous nucleus of the primary M7C3 carbides and thereby refined the primary M7C3 carbides.

Alkaline corrosion resistance of slag‐free self‐shielded titanium‐added metal‐cored welding overlay

“…The different carbon and chromium additions of overlays produced hypoeutectic, eutectic or hypereutectic structures [7]. Among these three structures, the hypereutectic high chromium iron-based overlays generally exhibited the better wear resistance because of the existence of the larger volume fraction of chromium carbides [8,9]. However, the formation of chromium carbides depleted the matrix of chromium and caused microcracks, which had a negative effect on corrosion resistance probably [10].…”