EFFECT OF Ni INTERLAYER ON CORROSION BEHAVIOUR OF CrN PVD COATING DEPOSITED ONTO PLASTIC MOULD STEELS

摘要

The plastics industry commonly uses moulds made of steels containing MnS inclusions. These inclusions play the role of heterogeneities, which make manufacturing easier. Moreover these types of alloy are thermal treatment free, cheap, and easily available. Unfortunately their use in corrosive conditions is prevented owing to the poor corrosion behaviour of the MnS particles. In order to mask these highly sensitive inclusions and to enhance the surface mechanical properties, hard physical vapour deposition (PVD) CrN coatings, elaborated at two Lit different temperatures, have been used. The coated specimens have been tested in saline corrosive solutions using electrochemical techniques. Corrosion results from dissolution of the anodic substrate through coating porosity, inherent to the PVD process, which leads to the deposit peeling off. The aim of the present study is to determine the corrosion resistance of an underlayer electroless nickel deposited coating on a 40CrMnMo8S substrate coated with PVD CrN.