Structure and properties of GCr15 modified by multiphase ceramic nanoparticles /Fe-C composite inoculants

GCr15 Bearing steel is widely used in the manufacture of rolling bearings and rolling ring. So the microstructure and performance of bearing steel are critical to the proper functioning of bearings and equipment. The modification is one of the effective methods to improve the microstructure and performance of materials. In this paper, Fe-Nb-Cr-C amorphous nanocrystalline inoculants are prepared by in-situ synthesis and rapid solidification techniques. Then, the microstructure of Fe-Nb-Cr-C inoculants are observed and analyzed. It is indicated by the test results that a large number of ceramic particles are distributed in the matrix of inoculants homogeneously. This paper also describes the heterogeneous nucleation of ceramic nanoparticles of inoculants in bearing steels and the Cr7C3 nanoparticles in the inoculant induces the formation of M7C3 carbides (mainly Cr7C3) in matrix of GCr15. Compared with traditional treat processing, after modification and heat treatment, the microstructure of the GCr15 has been optimized significantly as follows: the grain of the matrix of GCr15 is obviously refined; the number of the carbides particles is increased, and the sizes of all kinds of carbides particle are reduced obviously. The hardness, wear resistance, impact toughness and yield strength of the GCr15 bearing steel have been improved significantly, respectively. In particular, after modification, the tensile strength of the tempered GCr15 bearing steel reached 2025.7 MPa, and the elongation after fracture is about 1.54 times that of the unmodified GCr15. This high strength and toughness is difficult to achieve by other toughening methods.