Water-soluble Mim Binder Development And Technology Research

Metal injection molding(MIM) is an advanced near net shape process in efficiently producing complex parts and its key technique is binder design which is a combination of conventional plastic injection molding and powder metallurgy.This process consists of four main steps:mixing, injection molding, debinding and sintering. In this paper, the development of MIM and MIM binder were reviewed, water-soluble binder system is a low pollution method with good environmental effect and has promising perspective due to its cheap, fast and unpolluted debinding methods.Firstly, the design of the new binder system was created in which polyethylene goycol(PEG) was chosen as the water-soluble ingredient. Polyoxymethylens(POM) is the polymer ingredient which solubility parameter, the mixing free energy and the results of their mixing tests were tested. According experiment results, the ultimate new water-soluble MIM binder formula for POM PEG600, PEG 1000, SA, with corresponding contents 28%,50%,20%,2% respectively was determined.Secondly, the properties and application of PEG-POM binder were studied. The results showed that flow ability and wet ability of the binder were good and the feedstock was homogeneous. For rheological analysis of feeding, it was proved that the feed is a kind of non-newtonian fluid, reached MIM process requirements. The debinding of greenpart is excellent because more than 90% PEG can be removed safely in 80℃water within 5 hours. PEG and POM can be removed fully above the sintering temperature due to their good pyrolytic properties. The mechanical properties of sintering samples molded by the new binder system are good. After sintering processing, relative density of alloy reached 94.2 percent.