Study on Formation Mechanism of WC in Carburized Layer of Fe-1.57W Binary Alloy

Abstract

For the better application of the solid carburized processing with simple technology, easy operation, safety and reliability, economic mode, this paper studied the carburized layer of Fe-1.57W binary alloy after solid carburized treatment by OM, SEM, EDS, XRD. Its microstructure was observed and analyzed, and its surface hardness and hardness gradient in the section were measured. At the same time, the formation mechanism and morphology causes of WC were researched and conjectured from the thermodynamics, the crystallography and the valence electron. The results show that: After 930 °C × 8h solid carburized processing and water quenching, the surface hardness of the carburized layer of Fe-1.57W binary alloy is up to HRc59, and its microstructure is composed by M, γ, Fe3C and WC. Fe3C lies in the surface carburized layer. In adjacent layer, there is a layer with large size WC. At 930 °C, WC nucleates on {100} crystal planes in the austenite, and grows along the c-axis direction, under the mutual restriction among the crystal faces of (11 0), ( 2 0) and (2 0) or in the parallel crystal faces of (11 0) and ( 20), and then shows as thin strip, triangle, square, bow-shaped morphology, etc.