Electrochemical Behavior of 2Cr13 Steels by Duplex Treatment of Plasma Nitriding and WCrAlTiSiN Ion Plating
The poor corrosion resistance of 2Crl3 steel significantly affects its service life in marine environments,such as petrochemical,naval,and ocean engineering.Currently,strengthening methods for martensitic stainless steel are mainly limited to a single chemical heat treatment or coating,and there is relatively little research on composite treatment processes,especially nitriding and nano-multilayer coating.Plasma nitriding and multi-arc ion plating(WCrAlTiSiN multilayer coating)were used for the composite strengthening of 2Cr13 martensitic stainless steel,and its corrosion resistance in the natural Yellow Seawater environment was studied.2Crl3 was subjected to ion nitriding using an LDMC-20F pulsed glow discharge ion-nitriding furnace.The sample was placed on the cathode of a nitriding furnace,and the internal pressure of the furnace was reduced to 10 Pa.The voltage was adjusted to 750 V with a duty cycle of 73％,and the temperature was adjusted to 440 or 480℃.The internal NH3 pressure was maintained at 350 Pa,and the sample was heat-treated for 5 h.Untreated,"LPN,and HPN"samples were deposited with(W,Cr,Al,Ti,Si)N multilayer coatings using an industrial HCCE-280 cathodic arc evaporation system.Three W(99.99％),three Cr(99.99％),one Al-Ti-Si,and one Al-Ti alloy targets were selected.The current parameters for each target were adjusted according to the desired deposition rate.A very thin Cr bonding layer was deposited on the polished surface of the sample in an argon atmosphere,followed by the deposition of a CrN transition layer in a nitrogen atmosphere.Subsequently,in a mixed atmosphere of argon and nitrogen,a CrTiAlSiN layer was deposited on three Cr,one Al-Ti,and one Al-Ti-Si targets.Finally,multiple nanoscale WCrAlTiN layers were prepared as the outermost layer using programmed alternating deposition of WCrAlTiN and CrWAlTiN layers enriched with W and Cr,respectively.The structure,chemical composition,and hardness of the samples were characterized using X-ray diffraction,optical microscopy,transmission electron microscopy,and Vickers hardness testing.The results show that the nitrided sample is mainly composed ofε-Fe2-3N,γ'-Fe4N,and αN phases.The surface of the LPN and the HPN samples formed hardened layers of 50 and 90 μm thicknesses,respectively.The WCrAlTiN coating,with a thickness of 2.3 μm,was composed of CrN,W2N,TiN,and AlN phases.The surface hardness of the untreated sample was low and could not provide sufficient support,leading to an unsatisfactory hardness of the coated sample.After the composite treatment,the surface hardness of 2Crl3 steel increased from approximately 250 HV0.1 to 2 100 HV0.1.The electrochemical behavior of 2Crl3 in natural Yellow Seawater was tested using electrochemical impedance spectroscopy and potentiodynamic polarization.The results show that all samples exhibited a single equivalent circuit in the EIS spectra.Compared to the other samples,the"LPN+C"sample exhibited excellent corrosion resistance.Compared to the untreated sample,the Ecorr value of the LPN+C sample increased from-6.54× 10-1 V to-4.79× 10-1 V,the Icorr value and corrosion rate decreased by a single order of magnitude,while Rct increased by a single order of magnitude.The nitrided layer and WCrAlTiSiN coating can formed a protective barrier,effectively blocking charge transfer and current flow from anode to cathode.this improved the corrosion resistance of 2Crl3 steel in seawater.The composite reinforcement method of ion nitriding and multi-arc ion plating with nanocoating can effectively enhance the surface hardness and corrosion resistance of martensitic stainless steel,particularly in seawater environments,thereby extending the service life of martensitic stainless-steel parts in marine applications.
nitrided coatingplasma nitridingmulti-arc ion platingmicrohardnesselectrochemical corrosion
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