不锈钢激光熔敷纯Ni粉末涂层的组织和腐蚀行为
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摘要
以纯Ni粉末作为熔敷材料,用光纤激光器在316L不锈钢表面进行激光熔敷。用SEM、EDS、XRD分析熔敷涂层的组织形貌与物相组成,采用电化学方法研究涂层与基材在3.5%NaCl溶液中的腐蚀行为。结果表明:涂层表面光滑,微观结构致密,与基材结合良好,涂层主要为γ(Ni,Fe)固溶体和FeNi3相,从顶部到底部组织形态依次为等轴晶、柱状晶、胞状晶,界面结合区为平面晶;涂层的自腐蚀电位为-0.13 V,电流密度为5.012×10-7A/cm2,相比于不锈钢基材,涂层的自腐蚀电位提高0.16 V,电流密度降低55.33%,腐蚀阻抗值高于基材,涂层表面钝化膜无夹杂物,完整性更高,点蚀萌生更加困难,同时可降低点蚀扩展速率,保护不锈钢基材。
The pure Ni powder was deposited on the surface of 316L stainless steel with fiber laser.The microstructure and phase composition of the coating were analyzed by SEM,EDS and XRD.The corrosion behavior of coating and substrate in 3.5%NaCl solution was investigated by using electrochemical method.The results show that the surface of the coating is very smooth and the coating has a dense structure bonded well with the substrate.The coating consists ofγ(Ni,Fe)solid solution andFrom the top to bottom,the morphology of microstructure is equiaxed crystal,columnar crystal and cellular crystal in turn.The interface zone is planar crystal,the self-corrosion potential of coating is-0.13 V and corrosion current density is 5.012×10-7A/cm2.Compared with the substrate,the self-corrosion potential shifts positively by 0.16 V and the corrosion density of coating decreases by 55.33%.The corrosion impedance modulus of coating is also significantly higher than that of substrate.The passivation film on the surface of coating has higher integrity without inclusion defects,which makes the initiation of pitting become more difficult and can reduce the rate of pitting,and Ni coating acts to protect the stainless steel substrate.
The pure Ni powder was deposited on the surface of 316L stainless steel with fiber laser.The microstructure and phase composition of the coating were analyzed by SEM,EDS and XRD.The corrosion behavior of coating and substrate in 3.5%NaCl solution was investigated by using electrochemical method.The results show that the surface of the coating is very smooth and the coating has a dense structure bonded well with the substrate.The coating consists ofγ(Ni,Fe)solid solution andFrom the top to bottom,the morphology of microstructure is equiaxed crystal,columnar crystal and cellular crystal in turn.The interface zone is planar crystal,the self-corrosion potential of coating is-0.13 V and corrosion current density is 5.012×10-7A/cm2.Compared with the substrate,the self-corrosion potential shifts positively by 0.16 V and the corrosion density of coating decreases by 55.33%.The corrosion impedance modulus of coating is also significantly higher than that of substrate.The passivation film on the surface of coating has higher integrity without inclusion defects,which makes the initiation of pitting become more difficult and can reduce the rate of pitting,and Ni coating acts to protect the stainless steel substrate.
引文
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[2]PARDO A,MERINO M C,COY A E,et al.Pitting corrosion behaviour of austenitic stainless steels-combining effects of Mn and Mo additions[J].Corrosion Science,2008,50(6):1796-1806.
[3]PAN C,LIU L,LI Y,et al.Pitting corrosion of 304ss nanocrystalline thin film[J].Corrosion Science,2013,73:32-43.
[4]石林,郑志军,高岩.不锈钢的点蚀机理及研究方法[J].材料导报:综述篇,2015,29(12):79.
[5]AHMAD S,MALIK A U.Corrosion behaviour of some stainless steels in chlorinated gulf seawater[J].Journal of Applied Electrochemistry,2001(31):1009-1016.
[6]ELKHOSHKHANY N,HAFNWAY A,KHALED A.Electrodeposition and corrosion behavior of nano-structured Ni-WC and Ni-Co-WC composite coating[J].Journal of Alloys and Compounds,2016,695:1505-1514.
[7]王东生,田宗军,沈理达,等.激光熔覆技术研究现状及其发展[J].应用激光,2012,32(6):538-544.
[8]WANG Q Y,WANG X Z,LUO H,et al.A study on corrosion behaviors of Ni-Cr-Mo laser coating,316 stainless steel and X70 steel in simulated solutions with H2S and CO2[J].Surface&Coatings Technology,2016,291:250-257.
[9]XU X,MI G,CHEN L,et al.Research on microstructures and properties of Inconel 625 coatings obtained by laser cladding with wire[J].Journal of Alloys&Compounds,2017,715:362-373.
[10]孙焕,林晨,陶洪伟,等.真空高频感应熔覆Ni60-WC复合涂层的耐蚀性[J].中国表面工程,2013,26(6):35-41.
[11]曾维华,刘洪喜,王传琦,等.工艺参数对不锈钢表面激光熔覆Ni基涂层组织及耐腐蚀性能的影响[J].材料工程,2012(8):24-29.
[12]FARAHMAND P,KOVACEVIC R.Corrosion and wear behavior of laser cladded Ni-WC coatings[J].Surface&Coatings Technology,2015,276:121-135.
[13]MOUSTAFA S F,ABDEL-HAMID Z,BAHEIG O G,et al.Synthesis of WC hard materials using coated powders[J].Advanced Powder Technology,2011,22(5):596-601.
[14]CUI M,PU J,ZHANG G,et al.The corrosion behaviors of multilayer diamond-like carbon coatings:Influence of deposition periods and corrosive medium[J].RSC Advances,2016,6(34):28570-28578.
[15]朱敏,袁永锋,刘俊,等.Incoloy825合金在不同温度3.5%NaCl溶液中的腐蚀行为[J].中国腐蚀与防护学报,2016,36(6):631-636.
[16]LEI J,SHI C,ZHOU S,et al.Enhanced corrosion and wear resistance properties of carbon fiber reinforced Ni-based composite coating by laser cladding[J].Surface&Coatings Technology,2018,334:274-285.
[17]NEWMAN R C.Materials science:beyond the kitchen sink[J].Nature,2002,415(6873):743-744.
[18]DONIK Cˇ,PAULIN I,JENKO M.Influence of MnS inclusions on the corrosion of austenitic stainless steels[J].Materiali in Tehnologije,2010,44(2):67-72.