| LU Xian–jing,XIANG Zhi–dong.Microstructure Characteristics and Formation Mechanism of Co-Deposition Coating on Plain 45# Carbon Steel via Simultaneous Chro-mising and Nitriding by Pack Cementation Process[J],46(1):218-223 |
| Microstructure Characteristics and Formation Mechanism of Co-Deposition Coating on Plain 45# Carbon Steel via Simultaneous Chro-mising and Nitriding by Pack Cementation Process |
| Received:June 25, 2016 Revised:January 20, 2017 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2017.01.035 |
| KeyWord:Cr2N layer pack cementation 45 carbon steel corrosion resistance microstructure |
| Author | Institution |
| LU Xian–jing |
The State Key Laboratory of Refractories and Metallurgy, School of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan , China |
| XIANG Zhi–dong |
The 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 45# plain carbon steel by forming a Cr2N coating layer. Cr2N co-deposition coatings at different stages were obtained by holding the temperature for different durations at 1100 ℃. The microstructure and formation mechanism of the coatings were studied by using SEM, EDS and XRD. Corrosion resistance of the coatings was assessed by virtue of electrochemical anodic polarisation curves. Optimal coating was obtained for 45# steel Cr2N pack infiltration when holding time was 4 h. The coating consisted of a top Cr2N layer (≈15 μm), a deposited layer of Cr (≈10μm) and diffusion layer of Cr (≈15μm). The top Cr2N layer had strong (002) predominant crystal orientation. Carbide phases of Fe-Cr alloy and Chromium (Cr7C3, Cr3C2) were found in the deposited layer of Cr. In the simulated corrosive liquid of fuel cell, the self-corrosion potentials of 45# steel, 45# coating sample and 304L stainless steel were −0.521 V, −0.448 V and −0.299 V respectively, and self-corrosion current 230.63 μA•cm-2, 10.89 μA•cm-2 and 5.26 μA•cm-2 respectively. Coating samples showed secondary passivation and the corrosion current was 1.43 μA•cm-2 when corrosion potential exceeded 0.3 V. Compared with the uncoated steel, corrosion resistance of the Cr2N coated 45# steel increases significantly, and is superior to that of 304SS when the corrosion potential is more than 0.3 V. |
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