Microstructure And Properties Of YG30 And Steel Joints Using Filling Alloys

WC-Co cemented carbide has a high hardness, wear resistance and can be used at elevated temperatures; it therefore is used widely in industry. But cemented carbide products have some drawbacks such as limited size, simple form, high cost, poor toughness, etc., which limit its application to some extent. Connecting cemented carbide to steel has already become a main method to solve these problems.The purpose of the present work was to investigate the tungsten inert gas arc welding technique (TIG) of WC-Co cemented carbide and a medium carbon steel (Fe-0.45C wt.%). Six kinds of filler metals with different contents of Co-Fe-C and technically pure iron were designed in this experiment. By means of hardness testing, bend strength testing, X-ray diffraction (XRD) and scanning electron microscope (SEM), the microstructure, phase and bending strength of the welded joints was investigated. Great emphasis was paid on the type and forming mechanism of ηphase as well as the influence of filler metals composition on the structure and properties. The result showed that the η phase distributed at the interface of WC-Co cemented carbide and weld bead was Fe₃W₃C or C03W3C, which belonged to the type of M₆C. It was the existence of the η phase that lowered the bend strength of the welded joint seriously. There were big η phase on rupture surface. By using Co-Fe-C alloy with proper carbon content as filler metals, the formation of the η phase could be well restrained and the bend strength of the welded joint could be improved to 1.04GPa. Filler metal (0.6C-55Ni-40Fe wt.%) was the most optimized filler alloy.