Microstructural and wear investigation of high chromium white cast iron hardfacing alloys deposited on carbon steel

Abstract

The investigation of the microstructural development during solidification as well as wear performance of Nb and Mo added hypereutectic WCI hardface deposits with W and V as minor additives was aimed during the study. This would enable the development of the hardface deposits with superior abrasive performance for severe wear applications. The hardfacing alloys were deposited on carbon steel using self-shielded flux cored arc welding (FCAW) technique. Phase formation, microstructural and mechanical properties of hardface deposits were investigated in the as-deposited condition. The microstructural examination showed that the addition of alloying elements to the high-Cr WCI resulted in grain refinement of the primary proeutectic M7C3 (M = Cr and Fe) carbide phase. EDX analysis revealed that the addition of Nb and Mo resulted in the formation of MC (M = Mo and Nb) carbides which resulted in grain refinement and higher wear resistance. Phase investigation of the deposits using XRD analysis shows the existence of M7C3 for all alloys and MC carbides for alloy B, C and D along with the ferrite phase. The main wear mechanism observed for the base high-Cr WCI is abrasive wear, while hardface alloys with alloying addition showed surface delamination which was attributed to the presence of soft phase adjacent to the M7C3 carbides in the microstructure. Among all the alloys, hardface deposits prepared using a filler with 5.5 -Mo, 6 - Nb, 2 - W and 1 - V (wt%) addition showed highest wear resistance due to grain refinement, MC carbide formation and solid solution strengthening by W and V.