Investigation On Stripping Of Nitrides Hard Films Containing Cr

In this paper,stripping solutions composed of distilled water,chelating agents,oxidants,inhibitors and potassium hydroxide or sodium hydroxide are used to theremoval of multi-component hard reactive film of (Ti,Al,Zr,Cr)N,four-component hardreactive film of (Ti,Al,Cr)N and three-component hard reactive film of (Ti,Cr)N whichdeposited on the substrates of high speed steel (HSS), hard metal alloy and stainlesssteel by multi arc ion plating technology.The changes of the films mentioned above inthe removal process are observed.The stripping abilities of the stripping solutions withdifferent compositions combinations,concentrations and additive processes arecompared.The surface microstructure, surface composition and roughness of the coatedsamples before and after stripping process are analyzed.Moreover,the reactionmechanism in the removal process is also studied.As to the hard reactive films of (Ti,Al,Zr,Cr)N and (Ti,Al,Cr)N, stripping solutionscomposed of different compositions combinations such as potassium hydroxide orsodium hydroxide and distilled water;potassium hydroxide or sodium hydroxide,chelating agents and distilled water;potassium hydroxide or sodium hydroxide,chelating agents,oxidants and distilled water are conducted with various concentrationsand additive processes under constant temperature.The analysis for the surfacemicrostructure,surface composition and roughness of the coated samples before andafter stripping process shows that the first two groups of stripping solutions can’tremove the films.However, the last one can remove the films completely.Two steps areused to the removal of the three-component hard reactive film of (Ti,Cr)N.For the firststep,pretreatment of stripping solutions immerse is carried out.In the second step,potassium hydroxide or sodium hydroxide,chelating agents,oxidants and distilled waterare used to prepare stripping solution and the film is removed with variousconcentrations and additive processes.The analysis for the surface microstructure,surface composition and roughness shows that the film is removed completely.The results of the studies indicate that the single use of chemical method of stripping solutions composed of potassium hydroxide or sodium hydroxide,chelatingagents,oxidants and distilled water can remove the multi-component hard reactive filmof(Ti,Al,Zr,Cr)N,four-component hard reactive film of(Ti,Al,Cr)N and three-componenthard reactive film of (Ti,Cr)N completely by changing the compositions combinations,concentrations and additive processes.What’s more, there are no corrosion traces on thesurface of the substrates after removing.The films can maintain the original brightnessand be used for a second plating and use.The optimum compositions combinations,concentrations and additive processes of stripping solutions are obtained by the analysisof surface microstructure,surface composition and roughness of the coated samplesbefore and after stripping process.As to the multi-component hard reactive film of(Ti,Al,Zr,Cr)N and four-component hard reactive film of (Ti,Al,Cr)N,surfacemicrostructure is observed for the samples in different stages and the removal reactionis a random and uniform diffusion reaction till the films are removed completely.However, the removal of three-component hard reactive film of (Ti,Cr)N is carried outalong with the defects and the later removed film continues to fall off along with theprevious one till the end.