Study On The Structure, Performance And Forming Mechanism Of Iron-base Surface Composite By Cast-singtering Technique

With the correct compound designing, a composite layer with thickness of 3 to 5 millimeters was formed on the surface of casting by means of Cast-sintering technique.Microsturcture of the composite layer was analyzed with help of optical microscope, scanning electronic microscope(SEM), electronic probe microanalysis(EPMA) and X-ray diffraction(XRD). The compacting of the billet and the forming mechanism of the carbide reinforcement were studied based on thermodynamics and kinetics of reaction, sintering theory and the result of DTA. At the same time, the wear-resistance of the composite layer was studied under condition of dry sliding friction.The result of those sudies as follow:(l) An composite layer of definite thickness on the casting was gained by cast-sintering technique, and it has well wear-resistance.(2) The reinforcement of the composite layer is TiC or VC, which was exiguous and is well distributed. Martensite and Austenitic form the matrix of the composite. (Cr,Fe)7C3 is also a kind of reinforcement(3)The combine of the composite layer and master-alloy is metallurgic combination and has a very high combining-intensity. And that the interface is very clear without bad resultant.(4) The sintering type of the billet is an instaneous sintering with a little quantity of liquid. The sintering process of the composite layer accomplished well and the layer has high density. (5) The forming of thereinforcement is controlled by mechanism of dissolving and seperating out in liquid and mechanism of diffusing and solid-solution, and the effect of former is more important. The process of keeping high temperature after the reaction balance would cause the dissolving of the smaller grains and the growing up of the biger grains.(6) Under loads of 588 Newton, the wear-resistance of the TiC-Fe and VC-Fe surface composite are 3.14 and 4.20 times as that of chilling respectively. By analyzing the wear trace, the wear mechanism and the reason of their high wear-resistance are expounded.