TC4 合金微弧氧化层的耐磨性和耐蚀性

目的对比不同电解液体系中制备的陶瓷膜层的耐磨损和耐腐蚀性能,判断实验条件下陶瓷膜性能最优的电解液体系。方法在相同的电参数工艺下,分别在Na Al O2,(Na PO3)6和Na2Si O3电解液体系中对TC4合金进行微弧氧化处理,处理时间为15 min。分析陶瓷层的表面形貌、成分和相结构。进行干摩擦条件下的摩擦磨损实验,对比TC4合金及三种陶瓷膜的耐磨性。通过测试极化曲线,对比TC4合金及三种陶瓷膜的耐蚀性。结果在Na Al O2,(Na PO3)6,Na2Si O3电解液体系中获得的陶瓷层表面呈现出多孔和局部凸起的相似表面特征,但相组成存在差异,主要相分别为Al2Ti O5,Al PO4和Ti O2。摩擦磨损实验表明,在10 N载荷下,以Si3N4陶瓷球作为摩擦配副,陶瓷层的磨损失重相对基材均显著减小,其中(Na PO3)6-陶瓷层失重约为基材的1/22。极化曲线分析表明,在模拟油田采出液作为腐蚀液的条件下,与TC4合金相比,陶瓷层的Ecorr显著正移,Jcorr明显减小,其中(Na PO3)6-陶瓷层的Ecorr从-0.311 V正移至0.777 V,Jcorr从9.634×10-7A/cm2减小到2.595×10-8A/cm2。结论微弧氧化处理能够显著改善TC4合金的耐磨性和耐蚀性,其中(Na PO3)6-陶瓷层的综合性能较好,有望满足TC4合金服役于油田环境时的要求。

Wear and Corrosion Resistance of Microarc Oxidation Coatings on TC4 Alloy

Objective To compare the wear and corrosion resistance of coatings fabricated in different electrolytes, to obtain the electrolyte system producing ceramic coatings with best properties under the experimental conditions. Methods Microarc oxidation (MAO) treatments were conducted on TC4 alloy samples in NaAlO2 , (NaPO3 ) 6 and Na2 SiO3 electrolytes, respectively, with the same electrical parameters and the treatment time was 15 min. Besides, the surface morphology, chemical composition and phase constitutions of the ceramic coatings were analyzed. The wear resistance of the TC4 alloy and the ceramic coatings formed in different electrolytes was compared by friction and wear testing under dry friction condition. By testing polarization curve, the corrosion resistance of TC4 alloy and three ceramic coatings was comparatively analyzed. Results The results showed that the ceramic coatings fabricated in different electrolytes had similar surface morphology, with many small pores and local bulge on the surface, but they were built up by different phase constitutions. The main phases of the coatings fabricated in NaAlO2 , (NaPO3 ) 6 and Na2 SiO3 electrolytes were Al2 TiO5 , AlPO4 , TiO2 , respectively. Compared with the substrate, tribological test revealed that under the load of 10 N against Si3 N4 ball, the mass loss of all the coatings had a significant reduction, among which, the mass loss of coating formed in (NaPO3 ) 6 electrolyte was only 1 / 22 that of the substrate. In the simulated producing well solution, comparing ceramic coatings with TC4 alloy, the analysis results of polarization curves showed that the corrosion potential (Ecorr) was obviously changed to positive and the corrosion current (Jcorr) was significantly reduced. The Ecorr and Jcorr values of the coating formed in (NaPO3 ) 6 electrolyte were improved from -0. 311 V to 0. 777 V and reduced from 9. 634×10 -7 A / cm2 to 2. 595×10 -8 A / cm2 , respectively. Conclusion MAO treatments could significantly improve the wear and corrosion resistance of TC4 alloy, and the coating prepared in ( NaPO3 ) 6 electrolyte had relatively good comprehensive performance, with the potential of meeting the requirements for application of TC4 alloy in oilfield environment.