Study On The Structure And Properties Of NiCrN And NiCoCrAlYN Protective Coatings Deposited By Arc Ion Plating

The protective coatings was designed to improve the working life of the press roll worked in the corrosive wear condition.In this paper,the NiCrN coatings and NiCoCrAlY/NiCoCrAl YN composite coatings were deposited on the 42CrMo steels by arc ion plating?AIP?technique.The coatings were deposited with different N contents by controlling N₂ flow rate in the process of coatings deposition.The phase structure,adhesion strength,microhardness and corrosive wear resistance of the designed protective coating were systematically analyzed by X-ray diffractometer?XRD?,X-ray photoelectron spectroscopy?XPS?,scanning electron microscope?SEM?,Rockwell apparatus,microhardness tester and corrosive wear testing machine.The results were summarized as follows:?1?The main phase of NiCrN coatings were?Ni,Cr?solid solution,CrN and a small amount of metallic Cr.The contents of CrN phase was higher in the high-Cr NiCrN coatings than that of the low-Cr NiCrN coatings.The NiCoCrAlYN coatings were mainly comprised of?-Ni??'-Ni₃Al?CrN and AlN.With the N₂ flow rate increasing,the nitride content of the NiCrN and the Ni CoCrAl YN coatings increased,and the grain refinement occured at the same time.?2?The low-Cr NiCrN coatings?HF-2?showed better adhesion strength than that of the high-Cr coatings?HF-3?under the same N₂ flow rate.The low-Cr Ni CrN coatings had a little effect on N₂ flow rate,whose microhardness were about 600 HV_0.05.However,the microhardness of the high-Cr NiCrN coatings increased from 530 HV_0.05.05 to 710 HV_0.05with the increment of N₂ flow rate?0⁶00 sccm?.Besides,the microhardness of the NiCoCrAlY/NiCoCrAl YN composite coatings increased from 575 HV_0.05.05 to 730 HV_0.05,but the adhesion strength of which decreased from HF-2 to HF-3 with the increment of N₂flow rate?0⁴00 sccm?.?3?The results of electrochemical polarization curves showed that all of the coatings includinglow-CrNiCrNcoatings,high-CrNiCrNcoatingsandthe NiCoCrAlY/NiCoCrAlYN composite coatings exhibited higher corrosion potential and much smaller corrosion current density compared to the substrate,indicating the excellent corrosion resistance of the coatings.And the protective efficiency of these coatings were all above 80%.?4?The results of the experiment showed that,the pitting was the main factor of corrosivewearfailuremechanismoftheNiCrNcoatingsandthe NiCoCrAlY/NiCoCrAl YN composite coatings.The Ni CrN coatings had the best corrosive wear resistence when the N₂ flow rate was 200 sccm.The corrosive wear resistence of the NiCoCrAlY/NiCoCrAl YN composite coatings were significantly better than that of the NiCoCrAlY single coatings.Moreover,the corrosive wear resistance of the composite coatings increased with the increment of N₂ flow rate.