The V-epc Infiltration Casting Preparation Of Fe-based Surface Composites Infiltration Casting Mechanism,

In the paper, the cast-infiltration mechanism of WC reinforced HT300 matrix surface-layer composite fabricated by V-EPC and cast-infiltration process was studied, including the influence of cast-infiltraton parameter on infiltration depth, and the study on the interface in the composite material.First of all, for simulating the cast-infiltration process, a simple infiltration apparatus was designed to study the influence of the melting temperature and vacuum degree on infiltration depth, and melting temperature and vacuum degree varied in series experiments. The results show that the infiltration depth increases as the melting temperature and vacuum degree increases. The relating infiltration depth formula confirms to it.In addition, the possible interface reactions were calculated on thermodynamics. The resulte shows as is followed: there is the reaction W₂C = WC+W, then the formedW synthesizes with C to form WC or W₂C, or synthesizes with WC to form W₂C. The tendency of the latter is bigger than the former.The interface in the composite material in this paper is the third interface, on which tungsten carbide, high carbon chrominum iron and grey iron interact, forming interface reaction formation. The three matters were analyzed by Differential Thermal Analysis (DTA) to study the interface reactions. The samples gained by DTA were analyzed by Scanning Electron microscope (SEM) and X-Ray Diffraction (XRD). The results show that in the cast-infiltration process high carbon chrominum iron melted, tungsten carbide particle partly dissolved and the interface reaction formations were reformed WC and W₂C, M₆C and M₇C₃ carbide while M contained Fe,Cr and W; The dissolution and formation of tungsten carbide particles changed the original contain and shape of the tungsten carbide particles and the matrix, and the appropriate interface reactions were good for the matrix alloying, reducing stress concentration on the interface, increasing the interface bond strength and improving the abration resistance of the material. During the different matrice, tungsten carbide in the grey iron and high carbon chrominum iron matrix dissolved the most and the formations were the most. The composite layer formed when the energy flow and matter flowegsisted simultaneously. When there was only energy flow the composite layer didn't form. It was showed by that high carbon chrominum iron and tungsten carbide didn't form the metallurgical bond.