Microstructure and wear resistance of Fe-Cr-C-B-Nb hardfacing alloy

Fe-Cr-C-B-Nb wear resistant flux cored wire was deposited by self-shield open arc welding. The phase composition and precipitation sequence of hard phases in the surfacing layer were analyzed. And the effect of B and Nb content on microstructure and wear resistance were also studied by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffractometer (XRD). The experimental results showed that the microstructure consisted of the martensite, retained austenite, M23(C,B)6and NbC phase. NbC phase was precipitated preferentially than M23(C,B)6phase. When the content of B and Nb element reached 0.21% and 1.44% in the surfacing layer respectively, the hardfacing alloy indicated a high hardness and wear resistance. Therefore, the macro-hardness could reach 69 HRC±1.5 HRC and the wear loss was 0.037 6 g for the Fe-Cr-C-B-Nb hardfacing alloy. The excess B was not conducive to the precipitation of NbC phase, resulting in the solid solution strengthening of boride and matrix by Nb element. The results of abrasion test indicated that the exist of M23(C,B)6and NbC significantly improved the abrasion resistance of Fe-Cr-C-B-Nb hardfacing alloys.