Microstructural characteristics, mechanical properties and interfacial formation mechanism of tungsten alloy/steel composite structure fabricated by HIP co-sintering

In this study, tungsten alloy/steel composite structure has been successfully fabricated by co-sintering method using hot isotactic pressing (HIP). The microstructure and mechanical properties of co-sintered samples were investigated systematically. Experimental results show that dense co-sintered base materials were obtained with good tensile properties (870 MPa for 90 W-4.2Ni-1.8Fe-4Cu alloy and 1350 MPa for 30CrMnSiNi2A steel). The co-sintered joint contains five regions: the W alloy matrix, the diffusion-affected zone of the W alloy (n-carbides contain Fe3W3C and Fe6W6C), the reaction interlayer, the diffusion-affected zone of the steel ((Ni, Fe, Cu) solid solution), and the steel matrix. The interlayer shows solidification structure, which is composed of Fe0.64Ni0.36, CU0.81Ni0.19, Fe3W3C and Fe2W Laves phases. The eta-carbides transitional belt with thickness of 4-6 mu m formed along the W grain boundaries at the interfacial region between W alloy and interlayer, which is the weakest area of the interface according to the TEM and nanoindentation test results. Furthermore, the formation mechanism of the interfacial structure is deeply discussed. The interfacial shear and tensile strengths of the co-sintered specimen is 310 MPa and 148 MPa, respectively. This technique provides a reliable method of efficient preparation of tungsten alloy/steel composite structure. (C) 2021 The Authors. Published by Elsevier Ltd.