Common materials for metal injection molding

Metal injection molding is a near-net forming process suitable for the production of small, three-dimensional complex shapes and articles with special performance requirements. This technology is a new powder metallurgy near net shape forming technology which is formed by introducing modern plastic injection molding technology into the field of powder metallurgy.
 
The basic process is: preparing a variety of fine metal powder (generally less than 20 μm) with a predetermined ratio of a predetermined binder to produce a rheological property, and injecting a mold blank into the mold cavity through an injection machine. After the blank is removed by the binder and sintered at a high temperature, various metal parts can be obtained.
 
Powder particle size, tap density and particle shape are key performance indicators that determine whether a powder can be successfully used in a MIM process. The MIM process requires very fine raw material powders (~10 μm) to ensure uniform dispersion, good rheological properties and large sintering rates.
The ideal powder for MIM is: powder particle size 2 ~ 8μm; bulk density 40% ~ 50%; tap density 50% or more; powder particles are nearly spherical, larger than the surface. At present, MIM metal powder raw materials include iron, nickel, titanium, stainless steel, precious metals, super alloys and other materials. At the same time, it is developing in diversification, such as structural materials, functional materials, magnetic materials, and the like.
 
The methods for producing MIM powder mainly include a carbonyl method, an ultrahigh pressure water atomization method, a high pressure gas atomization method, a plasma atomization method, and a laminar atomization method. Different powder preparation techniques have different effects on the particle size, particle shape, microstructure, chemical properties, manufacturing costs, and the like of the powder.
 
Binder is the core of MIM technology, and an important difference between MIM and conventional powder metallurgy is the high binder content. The primary function of the binder is to act as a carrier for the flow of bonded metal powder particles and to maintain the shape of the workpiece after molding.