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Influence of process parameters on thickness and wear resistance of rare earth modified chromium coatings on P110 steel synthesized by pack cementation

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Journal of Rare Earths 2011年第4期29卷 396-400页

作者：林乃明谢发勤吴向清田伟 School of Aeronautics Northwestern Polytechnical University Tubular Goods Research Institute China National Petroleum Corporation

The pack cementation was employed to produce rare earth modified chromium coatings on P110 steel aiming at improving its performance and increasing the usage lifetime during operation. The orthogonal array design （OAD） was applied to set experiments. Contents of NH4Cl, types of RE, contents of RE, test temperature and soaking time were the main factors, and each factor was endowed with four levels. While the range analysis and analysis of variance were used to investigate the results of OAD tests on thickness and wear resistance. The results indicated that for a promising coating with higher thickness value and excellent anti-wear property, the test temperature was the most significant process factor. The potential promising conditions for chromizing treatment were： adding 1% NH4Cl and 1% LaCl3, maintaining the test temperature at 1000 oC for 8 h. The results of verification showed that the coating formed under the optimal process parameter had a valid thickness of 28 μm and a reduction of 0.32 mg in wear resistance test.

关键词： thickness wear resistance rare earth chromium coating P110 steel pack cementation

Microstructures and wear resistance of chromium coatings on P110 steel fabricated by pack cementation

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Journal of Central South University 2010年第6期17卷 1155-1162页

作者：林乃明谢发勤周俊钟涛吴向清田伟 School of Aeronautics Northwestern Polytechnical University Tubular Goods Research Institute China Natio nal Petroleum Corporation

In order to obtain a high-performance surface on P110 steel that can meet the requirements in oil/gas field environment, the chromium coatings were fabricated by pack cementation. The chromium coatings differed in with/without the addition of La2O3. Scanning electron microscope （SEM）, energy dispersive X-ray spectrometer （EDS）, X-ray diffractometer （XRD） and microhardness tester were employed to investigate the surface morphologies, surface element distributions, microstructures, phase constitutions and microhardness of the coatings. Friction-wear tests of the P110 steel substrate and the coatings were conducted in air at ambient temperature and humidity. The results show that ＇uniform and continuous coatings are formed on P110 steel regardless of adding La2O3 or not. The chromium coatings consist of Cr23C6, Cr7C3, and （Cr, Fe）7C3. The La2O3-added chromium coating is more beneficial in terms of surface morphology, microstructure, thickness and microharduess as compared with the coating without adding La2O3. Chromizing treatment significantly improves the surface hardness and wear resistance of the P110 steel. The wear resistance of the tested samples can be sorted in the following sequence： La2O3-coating 〉 no RE-coating 〉bare P110 steel.

关键词： chromium coating P110 steel pack cementation La2O3 microstmcture wear resistance

Balancing the corrosion resistance and through-plane electrical conductivity of Cr coating via oxygen plasma treatment

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Journal of Materials Science & Technology 2021年第2期61卷 75-84页

作者： Xian-Zong Wang Hong-Qiang Fan Triratna Muneshwar Ken Cadien Jing-Li Luo State Key Laboratory of Solidification Processing Center of Advanced Lubrication and Seal MaterialsNorthwestern Polytechnical UniversityXi'an 710072.China Department of Chemical and Materials Engineering University of AlbertaEdmonton.T6G 1H9Canada Laboratory for Microstructures Institute of MaterialsSchool of Materials Science and Engineering.Shanghai UniversityShanghai 200072China

Developing an electrically conductive and corrosion-resistant coating is essential for metal bipolar plates of polymer electrolyte membrane fuel cells(PEMFCs). Although enhanced corrosion resistance was seen for Cr coated stainless steel(Cr/SS) bipolar plates, they experience a quick decrease of through-plane electrical conductivity due to the formation of a porous and low-conductive corrosion product layer at the plate surface, thus leading to an increase in interfacial contact resistance(ICR). To tackle this issue, the multilayer Cr coatings were deposited using the magnetron sputtering with a remote inductively coupled oxygen plasma(O-ICP) in the present study. After the O-ICP treatment, a Cr oxide layer(Cr O*) is formed on the specimen surface. The Cr O*/Cr/SS has a remarkably lower stable corrosion rate(iss) than that of the native Cr oxides(Cr On/Cr/SS). Compared with Cr On/Cr/SS, the excellent performance of Cr O*/Cr/SS is attributed to a denser and thicker surface layer of Cr O* with Cr being oxidized to its highest valence state,Cr(VI). More importantly, the through-plane electrical conductivity of the specimens treated by the optimized O-ICP decreases much slowly than Cr On/Cr/SS and thus, the increament of ICR of Cr O*/Cr/SS after the potentiostatic polarization test is considerably smaller than that of Cr On/Cr/SS, which is benefited from the reduced issthat mitigates the deposition of corrosion products and hinders further oxidation of Cr coating. Therefore, Cr O*/Cr/SS proves to be a well balanced trade-off between corrosion resistance and through-plane electrical conductivity. The results of this study demonstrate that O-ICP treatment on a conductive metal coating is an effective strategy to improve the corrosion resistance and suppress the increase of ICR over the long-term polarization. The technique reported herein exhibits its promising potential application in preparing corrosion resistant and electrically conductive coatings on metal bipolar pla

关键词： Metal bipolar plates Oxygen plasma treatment chromium coating Corrosion resistance Electrical conductivity Polymer electrolyte membrane fuel cells