Boron addition in a non-equiatomic Fe50Mn30Co10Cr10 alloy manufactured by laser cladding: microstructure and wear abrasive resistance

Abstract

A non-equiatomic Fe(50)Mn(30)Co(10)Cr(10 )alloy was prepared by laser cladding, and the effects of boron addition on the microstructure, hardness and abrasive wear-resistance were investigated. Elemental powders were mixed using an attritor mill for 30 h and then applied by laser cladding on a stainless steel 316L substrate. The effect of boron addition (0.1, 0.66 and 5.40 at%) on the alloy microstructure was assessed using optical and electron microscopy, and the phase composition was studied using X-ray diffraction. The laser claddings were exposed to abrasive wear conditions using the dry sand/rubber wheel test. The microstructure of the laser claddings exhibited columnar dendrites formed by two crystalline structures (fcc and hcp) with the same chemical composition. The hcp structure was the result of the partial martensitic transformation of the fcc structure. Boron addition led to the formation of a eutectic phase along the interdendritic regions with a crystalline structure consistent with M2B-type borides (M = Cr, Fe). Hardness and abrasive wear-resistance of the laser claddings were strongly influenced by boron content. When boron content was increased from 0 at% to 5.40 at% the microhardness of the material was from 291 HV to 445 HV. Similarly, the boron content improved the behaviour against abrasive wear due to the increased volume fraction of borides in the microstructure. The high content of the boride phase in the laser cladding with 5.40 at% B allowed reducing the abrasive wear rate by more than 30% when compared with the alloy without boron content.