Effect of nitrogen alloying on the microstructure and abrasive impact wear resistance of Fe-Cr-C-Ti-Nb hardfacing alloy

Abstract

Abstract The effect of nitrogen additive on the microstructure and abrasive impact wear resistance of high chromium Fe-Cr-C-Ti-Nb hardfacing alloy, which developed by an open arc welding technique was investigated in this work. The phase structure and microstructures of the hardfacing alloys were studied by means of optical microscopy (OM), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectrometry (EDS) and transmission electron microscope (TEM). Moreover, the hardness of carbides in the hardfacing alloy was measured by nanoindentation test, and abrasive impact wear resistance was determined. Besides, the influence of variables on the wear behavior was investigated. The results show that, the high chromium Fe-Cr-C-Ti-Nb hardfacing alloys with different nitrogen additive mainly consist of primary (Cr, Fe)7C3 carbides, eutectic matrix and (Ti, Nb)(C, N) precipitates. With increase of nitrogen content in high chromium Fe-Cr-C-Ti-Nb hardfacing alloy, the primary carbides can be refined obviously. Meanwhile, the hardness of (Cr, Fe)7C3 is increased slightly from 18.7 GPa to 21.3 GPa, and that of (Ti, Nb)(C, N) is from 27.0 GPa to 27.6 GPa. Moreover, the volume loss of hardfacing alloys is decreased from 72 mm3 to 39 mm3. During abrasive impact wear test, the large primary carbides in the hardfacing alloy without nitrogen additive are fractured and spalled from the matrix, its abrasive impact wear resistance is low. While, the refined (Cr, Fe)7C3 carbides in the hardfacing alloy with nitrogen additive can be bended during the wear test, which increase its abrasive impact wear resistance. The lattice disregistry between (Ti, Nb)(C, N) and (Cr, Fe)7C3 is 6.15%, which indicates that (Ti, Nb)(C, N) can serve as heterogeneous nucleation sites for the primary (Cr, Fe)7C3 carbides. So that, the large primary (Cr, Fe)7C3 are refined and the abrasive impact wear resistance is improved. In addition, it is found that the volume loss of HC2N is increased with the increase of hardness, size, velocity and impact angle of the abrasive particles.