Study On Stripping Of(Ti,X)N Hard Nitride Films

A series of multi-component hard films,including(Ti,Al)N,(Ti,Zr)N and(Ti,Al,Zr)N films,were deposited on stainless steel or high speed steel substrates by multi-arc ion plating technology.The stripping processes of the films were developed by using the different combination of chelating agents,oxidants,inhibitors and sodium hydroxide and changing the concentrations of the stripping solutions,stripping temperature,and also the PH value of the stripping solutions.The surface morphology,composition and roughness of the coated samples before and after stripping and the uncoated substrates were measured and tested by the aid of Scanning Electron Microscopy(SEM),Engery Disperse Spectroscopy(EDS)and roughmeter.The changes of the three films with time under the different conditions including elements combinations,concentrations,PH value and reactive time were systematically investigated.The observation and the evaluation of the changes of the surface morphologies were presented by the aid of SEM.The(Ti,Al)N and(Ti,Zr)N films were deposited on stainless steel substrates by multi-arc ion plating and using the Ti-Al(50:50,at%)alloy targets,Ti-Zr(50:50,at%)alloy targets.In addition,the(Ti,Al,Zr)N films were deposited on high-speed steel substrates by using the pure Zr target and Ti-Al(50:50,at%)alloy target.The present investigation aims to strip these three films because they are the representatives of the hard nitride films which were widely used in the field of tools and molds.The studies on the stripping solutions and the stripping processes of the(Ti,Al)N and(Ti,Zr)N films revealed the following three circumstances.1 Stripping solution composed of the combination of chelating agent with sodium hydroxide or the combination of oxidant with sodium hydroxide.The films were not be stripped regardless how the concentrations,the PH values and the stripping temperature changed.The surface morphology,components,roughness of the soaked films changed little in comparsion with the coating films.2 Stripping solutions composed of the combination of chelating agents,oxidant and inhibitors with sodium hydroxide.The films were completely stripped in the environment of the optimum concentration,the higher PH value and the higher temperature(higher than 45 ℃).But the surface of the stainless steel substrate was seriously corroded.The same compositions were found from the both surfaces of the corroded substrate after cleaning and the uncoated surface.The roughness value of the stripped surface was less than the coated one but bigger than the uncoated one.3 Stripping solutions composed of the combination of the chelating agents,oxidant and inhibitors with sodium hydroxide.The films were completely stripped in the optimum environment with the optimum concentration,the PH value and temperature.The surfaces of the stainless steel substrates were not corroded in a certain time after the films strippinng.The stripped surface got in accordance with the uncoated one in the ways of surface morphology,the composition and also the roughness.As to the stripping of the(Ti,Al,Zr)N films,the results showed the followings.1 Stripping solution composed of the combination of chelating agent with sodium hydroxide or the combination of oxidant with sodium hydroxide.The films were not be stripped regardless how the concentration,the PH value and the stripping temperature changed.The surface morphology,components,roughness of the soaked films changed little in comparsion with the coating films.2 The(Ti,Al,Zr)N films were completely stripped when the best stripping solutions and the best stripping processes,obtained from the stripping experiments of the(Ti,Al)N and the(Ti,Zr)N films,respictively,or the improved stripping solution,were used.The surfacees of the high-speed steel substrates were not corroded in a certain time after the films stripping.The stripped surface got in accordance with the uncoated one in the ways of surface morphology,the composition and also the roughness.The results showed that the optimized combination of chelating agents,oxidant,inhibitors,and the sodium hydroxide for stripping solutions simultaneously accompanied with the optimized stripping processes were effective to strip the three films completely,which were deposited on stainless steel or high speed steel substrates by multi-arc ion plating technology.The surfaces of the substrates retained mentalic luster and were not corroded within a short time after stripping film.The purposes to strip hard nitride films were achieved.