The Research Of Process And Properties On Powder Injection Molding Of Fe-2Ni Based Alloy Steel

Powder Injection Molding, which abbreviation is PIM, is a new near-net-shape technology of combining powder metallurgy, powder ceramics and plastic injection molding technology. In other words briefly is that people use plastic injection molding technology to make metals and ceramics products.Metal powder injection molding is a new high technology that has powerful prospect. It has advantages in making high property products of complex geometry shapes and uniform tissue textures which are near final shapes. Binder is the key of PIM. In the research, who puts the point to the binder and debind has got the point of problem. In the paper, I have evaluated a suitable method for MIM's binder and debind techniques. This is to guide the research of binder and debind. Main jobs I did as follows:In the basic of Fe-2Ni alloy steel powder, I have designed two binders systems. It indicated that the binder 66PW+10HDPE+20EVA+4SA was suitable for Fe-2Ni MIM.Influence of key injection molding process parameters on the quality of the injection-molded specimens is studied and the parameters are optimized using orthogonal arrays experimental design and statistical analysis method. The result shows that not only the levels of parameters but also some interaction between parameters have great influence on the quality of the green parts. The optimized injection parameters are as following: injection pressure 14MPa, injection temperature 140℃, injection speed 80mm/s and holding pressure 8MPa.The process of solvent debinding and thermal debinding were researched. The solvent I choose were n-Heptane and n-Hexane. After solvent debinding was thermal debinding process. Suitable process of solvent debinding and thermal debinding was determined. It indicated that at the temperature of 40℃, 66PW+10HDPE+20EVA+4SA system of binder, in the n-Hexane solvent debinded 8 hours could get best specimens. After that I was according to TGA curves of binder to design the best thermal debinding method. This method can debind efficiency and shorten the time. The specimen I got was regular without defects.Sintering process was designed. It indicated that use pre-sintering + sintering process could reduce the effect of oxidation.The specimens were tested after heat treatment. It indicated that the specimen's density was the highest in the sintering temperature of 1370℃, and the hardness was the highest in the sintering temperature of 1360-1370℃. The specimen could get the highest tensile strength in sintering temperature of 1390℃and tempering temperature of 400℃. Then was the 1370℃sintering temperature.It indicated from analysis of fracture of specimen that the tensile fracture had clearly tear-corrugation. It belongs to ductile fracture. But it could also see some defects such as holes and crackles.