| ZHOU Yong,XU Long,ZHOU Shuang,DONG Hui,GUO Peng-fei,YANG Zi-chen,ZHANG San-qi.Effect of Grain Growth Orientation and Morphology of Laser-cladded 316L Coating on Its Corrosion Resistance[J],52(5):378-387 |
| Effect of Grain Growth Orientation and Morphology of Laser-cladded 316L Coating on Its Corrosion Resistance |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.05.037 |
| KeyWord:laser cladding overlap ratio 316L grain orientation corrosion resistance |
| Author | Institution |
| ZHOU Yong |
School of Material Science and Engineering, Xi'an Key Laboratory of High Performance Oil and Gas Field Materials, Xi'an Shiyou University, Xi'an , China |
| XU Long |
School of Material Science and Engineering, Xi'an Key Laboratory of High Performance Oil and Gas Field Materials, Xi'an Shiyou University, Xi'an , China |
| ZHOU Shuang |
Gujiao Xishan Power Generation Co., Ltd., Taiyuan , China |
| DONG Hui |
School of Material Science and Engineering, Xi'an Key Laboratory of High Performance Oil and Gas Field Materials, Xi'an Shiyou University, Xi'an , China |
| GUO Peng-fei |
School of Material Science and Engineering, Xi'an Key Laboratory of High Performance Oil and Gas Field Materials, Xi'an Shiyou University, Xi'an , China |
| YANG Zi-chen |
School of Material Science and Engineering, Xi'an Key Laboratory of High Performance Oil and Gas Field Materials, Xi'an Shiyou University, Xi'an , China |
| ZHANG San-qi |
School of Material Science and Engineering, Xi'an Key Laboratory of High Performance Oil and Gas Field Materials, Xi'an Shiyou University, Xi'an , China |
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| Abstract: |
| Laser cladding is an advanced surface modification technology, which can be used to prepare coatings wear resistance, corrosion resistance, oxidation resistance, and other properties on the surface of metal substrates. Coatings prepared by laser cladding can change the orientation and morphology of the tissue. In this paper, the effects of grain orientation and morphology on the corrosion resistance of the 316L cladding layer were studied. The Q235 steel plate of 160 mm×60 mm×8 mm was polished clean at laser power of 900 W, scanning speed of 3 mm/s, spot diameter of 2 mm/s, and powder feeding rate of 6 g/min, and with argon as the protective gas. Under the same conditions, the 316L cladding layers with 20%, 35%, and 50% overlap ratio were prepared by laser cladding on the substrate with the equipment of model JHM-1GX-3000P. Specimens were cut with wire cutting and the sections polished and etched with aqua regia. Then, the microstructure of the cladding layer was observed with metallographic microscope and scanning electron microscope. The element distribution of the cladding layer was analyzed through EDS, and the phase composition of the cladding layer was analyzed through XRD. The corrosion resistance of the cladding layers with different overlap ratios was tested by electrochemical workstation in 3.5wt.% NaCl solution at room temperature, and the corrosion morphologies of the cladding layers after the test were observed through SEM. The results showed that the overlap ratio affected the forming quality of the cladding layers. The cladding layers with the 20% and 35% overlap ratios had no obvious pores, but there were large pores at the bottom of the cladding layer with 50% overlap ratio due to poor fusion. And the increase of the overlap ratio increased the transition layer area between the coating and the substrate but had no effect on the phase composition of the cladding layers, both of which were γ-phase. Due to the partial remelting and tempering brought about by the lap joint, the cladding structure was recrystallized, and transverse columnar crystals and cellular crystals appeared in the overlapping part of the cladding layer. For the cladding layers with overlap ratios of 20%, 35%, and 50%, the content of transverse columnar crystals gradually increased to 25%, 38%, and 41%. The electrochemical test results showed that the self-corrosion potentials of the cladding layer under different lap ratios were –441, –508, and –331 mV, respectively, and the self-corrosion current densities were 19.90, 3.73 and 1.34 µA.cm–2. The impedance value increased with the increase of the overlap ratio, and the corrosion resistance of the coating increased with the increase of the transverse columnar crystal content. The overlap leads to the transformation of the grain orientation and morphology in the overlapped region of the cladding layer. The grains are transformed from equiaxial to transverse columnar crystals, and the content of transverse columnar crystals increases with the increase of the overlap ratio. Transverse columnar crystals replace equiaxial crystals, and the grain boundaries of transverse columnar crystals are much larger than those of equiaxial crystals. Transverse columnar crystals increase the transmission distance of the corrosive medium, resulting in a significant improvement in the corrosion resistance of the cladding layer. |
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