Micro-structural characteristics of Fe–40 wt%Cr– xC hardfacing alloys with [1.0–4.0 wt%] carbon content

Abstract

The current study produces a series of Fe–40Cr– xC hardfacing alloys deposited by gas tungsten arc welding (GTAW). These hardfacing alloys are especially designed to various types of carbides and the microstructure at room temperature is presented. Depending on the four different graphite additions in these alloy fillers, this research produces hypoeutectic, near eutectic, and hypereutectic microstructures of Fe–Cr phase, (Cr,Fe) 23C 6, and (Cr,Fe) 7C 3 carbides on hardfacing alloys, respectively. Findings show Si to partition strongly into the Fe–Cr phase during solidification with very low solubility in (Cr,Fe) 23C 6 and (Cr,Fe) 7C 3 carbides. The cross-section analysis indicates epitaxial solidification with planar front growth at the interface between hardfacing and the substrate. Furthermore, eutectic growth exists in the near interface as hardfacing composition falls in the hypereutectic region. The microstructures in middle zone are similar to that of the near surface, causing uniform hardness profile. Finally, hardness of the hypereutectic alloy with 4.05 wt% C is about three times higher than that with 1.35 wt% C. Maximum cladding hardness is about six times higher than that of the substrate due to the massive primary carbides.