Q235钢表面Ni-Cr电镀层的组织及性能

为提高Q235钢的表面防护性能,对其进行表面电镀Ni-Cr处理,并采用正交试验对电镀Ni-Cr工艺进行优化。采用X射线衍射仪(XRD)、扫描电镜(SEM)和激光共聚焦显微镜(OM)分别对镀层进行物相表征和形貌观察,利用显微硬度计、磨粒磨损机和电化学工作站对镀层硬度和耐蚀性进行研究。结果表明:以镀层沉积速率为指标,正交试验所得电镀Ni-Cr优化工艺为柠檬酸钠含量30 g/L,镀液pH值3.0,电流密度20 A/dm~2,电镀温度35℃,镀层沉积速率可达40.17μm/h;Ni-Cr镀层相结构由γ-Ni和Cr_(1.22)Ni_(2.88)组成;镀层表面平整,表面形貌为密集球形颗粒;与基体相比,正交试验所得Ni-Cr镀层硬度提高了81.62~649.08 HV_(2N),磨损率减少了9.14~29.99mg/cm~2,自腐蚀电位提高了2.05~121.28 mV。

Microstructure and Properties of Ni-Cr Electroplated Coating on the Surface of Q235 Steel

In order to improve the surface protection property of Q235 steel,Ni-Cr electroplated coating was prepared on it,and the process conditions were optimized through orthogonal experiments.Morphology and phase composition of the coating were analyzed by XRD,SEM and OM,and the hardness and corrosion resistance of the coating were analyzed by microhardness tester,abrasive wear machine and electrochemical workstation,respectively.Results showed that the optimized operating conditions through orthogonal test were obtained based on the deposition rate as the evaluation index:sodium citrate 3.0 g/L,pH=3.0,current density 20 A/dn2,temperature 35 ℃.The deposition rate of the coating reached 40.17 μm/h and the Ni-Cr electroplated coating was composed of γ-Ni and CrL22Ni2.8s.The surface of the Ni-Cr coatings was smooth,with the dense arrangement of spherical panicles.Besides,the microhardness of the Ni-Cr coating was increased by 81.62-649.08 HV2N,and the wear rate was decreased by 9.14-29.99 mg/cm2,as well as the free-corrosion potential was improved by 2.05-121.28 mV,compared with those of the substrate.