CrN Nitriding Duplex Process Study

The surface properties of mold like wear resistance, corrosion resistance, resistance tohigh temperature oxidation can be improved by various surface treatment techniques.Surface treatment can also extend the life time of mold by several times or even dozens oftimes. Traditional methods include surface chemical treatment such as nitriding,carburizing, boriding and carbonitriding. There are also some coating methods like thermalspraying and electroplating. Surface technology develops rapidly in the recent years. Manynew technologies were introduced. Vapor deposition is one of the most rapid growing andwidly used technology. Depositing hard coatings on the mold surface can improvesignificantly the wear resistance and extend its life time.Depositing CrN coating by multi-arc ion plating on the mold suface can improve thewear resistance, corrosion resistance and high-temperature oxidation-resistant of mold. It isa proven effective method of protection mold. But PVD coated CrN coating is very thinthough its hardness is very high. Its thicknes is normally around3-8micron. The substrateof mold material is very soft and cannot support the coating when load force is big. Thecoating still fails.Practice has proved recently that nitriding layer under the PVD coating will supportthe hard coating well and extend the life time of mold. It will combine the advantage of thehigh strength of nitriding layer and the wear resistance property of PVD hard film. Butnormal nitriding process is very time cosuming and not environmental friendly. Nitridingand PVD process are separated. The investment is big and process is complicated. There iswhite layer left on the nitriding surface. The surface after nitriding can be contaminatedagain before it moves into PVD process. It will affect the adhesion between nitriding layerand PVD coating and thus the performance of mold. This research studies the best parameter setup of the duplex CrN coating (includingion nitriding) in one machine and one process. It is also investigated that in what conditionthis duplex coatig can replace nitriding plus CrN and still has good wear resistance result.It will be a good solution for the surface treatment of high loading mold with reliablequality, low cost and also environment friendly.