Local composite reinforcements of WC/Fe-C type obtained in-situ via SHS synthesis in gray cast iron castings

Abstract

A new method of the in-situ fabrication of local composite zones (LCZs) that are reinforced by tungsten carbides (WCs) in a gray cast iron matrix was presented. The synthesis reaction of the WCs was performed by placing reactive inserts that contained reactants (in the form of a tungsten-and-graphite powder) in a mold cavity. The high temperature of the liquid metal initiated the synthesis reaction of the WCs. As a result, homogenous LCZs with 10-mm thicknesses were manufactured. Samples that were taken from the LCZ region were analyzed by considering their structure, microstructure, mechanical properties, and wear resistance. An investigation that was carried out with the diffraction of high-energy synchrotron radiation confirmed the presence of the WC phase, which was caused by the reactive infiltration phenomena. The microstructural observation revealed the existence of the WCs in the form of faceted crystals. The hardness of the composite zones ranged around average levels of 647 HV30, which was a more-than-three-fold increase as compared to the original matrix (gray cast iron). These results were reflected in wear tests, which indicated a significant improvement of the wear resistance as compared to gray cast iron and reference materials such as martensitic steel and high-chromium cast iron.