Study On Properties And Application Of New Stellite Alloy Prepared By Metal Powder Injection Molding

Stellite alloys are used in aerospace,medical,automotive and other industries due to their superior mechanical properties at both room temperature and high temperature,excellent chemical resistance,and good biocompatibility.In this paper,Stellite alloys with different chemical compositions were prepared by metal powder injection molding technology.The chemical compositions,microstructure,macroscopic mechanical properties and their relationship were studied.A new Stellite alloy that can be used in the saw blade industry was designed,and the powder injection molding process for the workpiece was developed to prepare the cutter head.The main results are as follows:Stellite alloys with different content of molybdenum,tungsten,and carbon were designed by corresponding surface design methods.The macroscopic mechanical properties were analyzed.It was found that mixing of molybdenum and tungsten decreasedthe tensile strength of the Stellite alloy by more than 50%.When the content of carbon was fixed,the hardness of chrome-cobalt-molybdenum Stellite alloy is higher than that of the chrome-cobalt-tungstellite alloy with the high-tungsten-high-carbon Stellite alloy as an exception.The final compositional variables were molybdenum and carbon based on the analysis of the macroscopic mechanical properties.The analysis of microstructure and phase for the chrome-cobalt-molybdenum Stellite alloy showed that increasing the content of Mo might promote the carbides transformation from M₇C₃-type carbides to M₂₃C₆-type carbides and slightly increase the content of carbides.Increasing the content of carbon will increase the content of bothM₇C₃-type and M₂₃C₆-type carbides.The microstructure was quantitatively characterized by image segmentation technique to obtain the area fraction of each phase and hole of the chromium-cobalt-molybdenum Stellite alloy.A regression equation between chemical composition,microstructure,and hardness was established to verify the reliability of the model.The third phase M₂₃C₇ can be observed under the condition that Mo/C ratio is greater than 2.11 and the content of carbon is higher than 0.152wt.%.The hardness of M₂₃C₆ carbide,M₇C₃ carbide,and Fcc-Co matrix is predicted to be 70.88 HRC,73.23 HRC,and 35.66 HRC,respectively,which is basically consistent with the previous reports in the literatures.At the same time,a composition of new Stellite alloy with a hardness of about 50 HRC is designed.We prepared the pre-alloyed powder according to the composition of the novel Stellite alloy,and produce the cutter head workpiece using metal powder injection molding process.The ID3 algorithm is used to generate the decision tree to study the injection molding process.The selection order of the four parameters in the injection molding is provided and some feasible injection processes are suggested.The tensile strength of the cutter head is 674 MPa,and the hardness is 50.4 HRC.A pilot test is under consideration.