Peculiarities of interface structures in AISI M2 high-speed steel in relation to carbide phases

It was experimentally proved that the decohesion of carbides with the matrix facilitates plastic deformation of the AISI M2 high-speed steel during fracture and intensifies surface wear of the cutting tool manufactured of this steel. Using high-resolution scanning transmission electron microscopy, the interfaces between the tempered matrix and M₆C and MC carbides in the AISI M2 high-speed steel were investigated in detail down to the atomic scale for the first time. It was shown that M₆C/matrix interface exhibited only the incoherent interface, while MC/matrix interfaces were predominantly partially coherent. That predicts better cohesion of MC carbide with the matrix, which can be used to provide tailored microstructure and hence improved properties of the steel. Additionally, new insights are provided into the iron-chromium carbide (identified as Fe₁₄Cr₂C) nucleation on MC heterogeneous nuclei sites on the atomic scale.