Thermodynamics and Morphological Fractal Characteristics of WC Particulates Reinforced Steel Matrix Composites by Composite Electroslag Melting and Casting

Abstract

The composite electroslag melting and casting technology was adopted to produce 45 wt% WC particulate reinforced steel matrix composites. The results indicated that the WC formation showed a dominant position and displays in a triangle or rectangle in the WC reinforced steel matrix composites. As a reference plane, WC grains in the $(0001)$ surface grew up into a stack structure in the way of hierarchical formation along the $\left\langle {0001} \right\rangle$ direction, finally formed a three-dimensional shape with the $(0001)$ surface in a triangle. The fractal dimensions of WC present different changed with the transformation of the heat treatment process. When quenched and tempered at high temperature, the fractal dimension value of two types of WC appeared, and WC phases showed two groups of different fractal structure with different particle size and quantity. The larger fractal dimension difference $\Delta D$ corresponded to Fe₃W₃C compound carbides, with the smaller $\Delta D$ to WC particles which keeps the properties and morphology under the state of forging and annealing. The higher the quenching or tempering temperature, the larger the fractal dimension difference $\Delta D$ and the greater change of the morphology of WC were obtained.