| HU Yong-qi,XIANG Zhi-dong.Corrosion Resistance and Application of Martensitic Stainless Steels with an External Cr-N Coating Layer Formed by Pack Cementation Process[J],48(6):282-286 |
| Corrosion Resistance and Application of Martensitic Stainless Steels with an External Cr-N Coating Layer Formed by Pack Cementation Process |
| Received:November 19, 2018 Revised:June 20, 2019 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2019.06.034 |
| KeyWord:Cr2N coating pack cementation process martensitic stainless steel corrosion resistance |
| Author | Institution |
| HU Yong-qi |
State Key Laboratory of Refractories and Metallurgy, School of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan , China |
| XIANG Zhi-dong |
State Key Laboratory of Refractories and Metallurgy, School of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan , China |
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| Abstract: |
| The work aims to study the feasibility of increasing the corrosion resistance of martensitic stainless steel 440A by depositing a Cr2N coating layer. The martensitic stainless steel deposited with Cr2N coatings was obtained at 1100 ℃ after 4 h pack cementation process. The microstructure of the coatings was studied by SEM, EDS and XRD. Corrosion resistance of the coatings was preliminarily assessed by polarization curve and then further evaluated by immersion test in 0.5 mol/L H2SO4+ 2 mg/L F– at 60 ℃. Dense Cr2N coating was obtained at 1100 ℃ for 4 h in a powder pack 30Cr2N-2NH4Cl-68Al2O3. The coating consisted of a top Cr2N layer (≈17 μm) and a rich diffusion layer of Cr (≈19 μm). The top Cr2N coating was smooth, compact and free of cracks and pinhole defects. In the simulated corrosion solution of PEMFC, the self-corrosion potentials of original stainless steel sample and coated stainless steel sample were -0.623 V and 3274 μA/cm2 and -0.212 V and 0.0362 μA/cm2 respectively. In the immersion test, the coated stainless steel sample had no weight loss for 12,000 h at room temperature in 0.5 mol/L H2SO4+2 mg/L F– solution, while the original stainless steel sample dissolved rapidly at weight loss of 0.007 g/h. On the other hand, the coated stainless steel sample had no weight loss for 800 h at 60 ℃ in 0.5 mol/L H2SO4+2 mg/L F– solution, while the original stainless steel sample dissolved at weight loss of 0.252 g/h. Therefore, the corrosion resistance of martensitic stainless steel deposited with Cr2N coating on the surface is obviously improved compared with the original one. |
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