脉冲电沉积WC-Co-Ni镀层的制备及性能研究

Pulse Electrodeposition for WC-Co-Ni Coating Preparation and Performance

目的提高WC-Co-Ni纳米晶复合镀层的综合性能。方法利用脉冲电沉积法制备WC-Co-Ni纳米晶复合镀层,分析镀层的结构、表面形貌及元素成分,测试镀层的显微硬度。对WC-Co-Ni纳米晶复合镀层和304不锈钢进行5%(质量分数)H2SO4溶液浸泡实验,计算腐蚀速率,对比其耐蚀性。结果当脉冲参数为阴极电流密度5 A/dm2、脉冲占空比50%、脉冲频率2000 Hz时,施镀2 h制备的WC-Co-Ni复合镀层为纳米晶结构。镀层表面平整、光亮,无裂纹,由立方晶型的Ni、六方结构的WC和立方晶型的Co组成,WC-Co颗粒均匀弥散在纳米晶Ni镀层内,且m(Ni)∶m(W)∶m(C)∶m(Co)=6∶2∶1∶1。WCCo纳米颗粒起到了促进形核的作用,晶粒尺寸大多分布在20 nm左右。WC-Co纳米颗粒对镀层起到了弥散强化作用,使复合镀层的显微硬度达到600HV。在浸泡腐蚀实验中,随着温度从20℃升高至80℃,复合镀层的腐蚀速率增加缓慢,20℃下的腐蚀速率仅为0.4192 mm/a,80℃下的腐蚀速率也低于20mm/a。结论脉冲电沉积法制备的WC-Co-Ni纳米晶复合镀层硬度高于传统的不锈钢材料,耐蚀性也优于304不锈钢,综合性能较好。

Objective To improve the comprehensive performance of WC-Co-Ni nanocrystalline composite coatings. Methods WC-Co-Ni nanocrystalline composite coatings were prepared by pulse electrodeposition,the structure,the surface morphology and the elemental composition were analyzed,microhardness of the composite coatings was tested. The 304 stainless steel and the composite coatings were immersed in H2SO4 solution of the mass fraction of 5%,the corrosion rate was calculated and their corrosion resistances were compared. Results It was showed that when the pulse parameters were the follows,i. e.,5 A / dm2 cathodic current density,pulse duty ratio 50%,the pulse frequency of 2000 Hz and the plating time 2 hours,the prepared WC-Co-Ni composite coating formed a nanocrystalline structure. At these parameters,the coating,composed by cubic crystal Ni,hexagonal WC and cubic crystal Co,was smooth and bright without cracks. The WC-Co particles uniformly diffused in the Ni nanocrystalline coating layer and m（ Ni） ∶ m（ W） ∶ m（ C） ∶ m（ Co） = 6∶ 2∶ 1∶ 1. WC-Co nanoparticles played an important role to promote nucleation and the grain size was mostly about 20 nm. WC-Co nanoparticles had a strengthening effect on the coating dispersion,making the microhardness of the composite coating reach to 600 HV. The immersion test showed that the corrosion rate of the composite coating increased slowly when the temperature raised from 20 ℃ to 80 ℃,and the corrosion rate was only 0. 4192 mm / a at 20 ℃ and less than 20 mm / a at 80 ℃. Conclusion The hardness,corrosion resistance and comprehensive performance of the WC-Co-Ni nanocrystalline composite coatings are superior to the traditional 304 stainless steel.