Abstract: The friction behavior is a very complicated problem during powder forming. There are many factors affecting the friction behavior, which include properties of powder and dies, morphology and size of powder, surface condition of dies, relative velocity between dies and powder, properties of lubricant, temperature of die and powder, and so on. The existence of friction causes low density, uneven density distribution, and die wear, thereby affecting the performance, dimension precision and application range of powder metallurgy products. Friction will easily cause the failure of PM parts, especially those with complex shape and large thickness and dimension. The complication of friction behavior makes it difficult to be accurately measured and expressed, and the researches on it are not many, so it is difficult to make further research. Foreign research progresses of friction behavior in powder forming process are summarized, and two common methods of measurement and expression of friction are introduced, namely instrumented dies method and shear plate method. This will offer reference for further research of friction behavior in powder forming and for improving the performance of PM parts.

Key words: Compaction, Density, Friction models, Powder