During the last decade,the duplex treatment,i.e.prior plasma nitriding (PN) plus plasma assisted chemical or physical vapor deposition (PACVD,PAPVD) of hard coatings,has been successfully employed to the metal-shaping tools,die-casting moulds and extrusion dies (TMDs).The greatly improved performance and lifetime of these TMDs are attributed to the good properties of coating,high hardness and toughness of substrate,and excellent combination between coating and substrate.With the manufacturing requirements for high quality of TMDs,for PN of the duplex treatment,its important to attain a uniform and defect-free nitrided diffusion layer in substrate and meantime avoid the formation of white layer,which is detrimental to the adhesion properties of coating to substrate.It is more important,moreover,to precisely control the depth and hardness of nitrided diffusion layer,because a nitrided diffusion layer with a suitable depth and hardness may provide good support for coating,but the excessive depth and hardness of nitrided substrate may result in embrittlement and premature failure for TMDs,in particular for those with thin walls,for instance,the multi-microport extrusion dies.