Abstract: The influences of mild steel container on Hot Isostatic Pressed powder metallurgy superalloys is studied in this paper. It is concluded that there are some interaction of the mild steel on the hot pressed compact.The diffusiou of alloy elements will result in forming such zones which may be poor in alloy elements or rich in iron on the surface layer of the compact. The thickness of this layer varies with HIPing temperature and HIPing time. Meanwhile non-γ' phase area will form in the surface layer, as the consequence of the iuteraction. An equation was obtained to describe the relationship between the diffusion depth and the time at different HIPing temperature.The hardness from the surface layer to the core of the specimen was measured as well.The influence of carbon content of the mild steel was also discussed.