Decarburization Controlling Of Microwave-sintered WC-Co Alloys And VC’s Effects On The Microstructure And Properties Of The Alloy

In preliminary studies by our group, we found that decarburization formed and decreased gradually from surface to the center has appeared in microwave sintered WC-Co alloys, which affected bending strength of the alloy seriously. By microwave sintering YG12and YG13alloys, the reasons for decarburization during the processing had been studied. Moreover, adding carbon black in the specimens and increasing surrounding carbon potential methods to prevent the decarburization. In this work, VC was used as the grain growth inhibitor in the process of preparation of microwave sintering WC-12Co-xVC alloys. And with the addition of VC, impact on properties and microstructures of WC-Co alloy under microwave conditions had been studied.This work made the following conclusions:(1) When samples microwave-sintered in N2atmosphere, YG12and YG13alloys appeared decarburization, and the surface of samples decarburized severely than the internal. Decarburization was caused by the oxidation of samples, in which case, oxidation, sintering atmosphere decarburization and microwave effects made C diffusion rate increased and the C/W ratio in cobalt phase out of balance.(2) Three methods were used to control decarburization of the alloys. Under appropriate process, when4.5wt%black carbon was added, bending strength of YG12alloys was significantly increased to3172MPa.(3) The microstructure of microwave sintering WC-12Co-xVC alloy which sintered at1420℃for10min, have shown uniform, fine-grain, grain unimodal and without abnormal grain growth.(4) With the increase of sintering temperature and VC contents, the alloy’s relative density increased simultaneously. Besides, hardness increased with incremental VC content. And when VC content was0.3wt%, a turning point was appearred, and the alloy’s hardness increased rapidly, until the maximum hardness reached91.9HRA.