| REN Xiangyu,SUN Wenlei,TIAN Shuang,WANG Qiuyu.Effect of Powder Feeding Rate on Microstructure and Properties of Internal FeCoNiCrMo0.2 Coating by Laser Cladding[J],54(5):188-202 |
| Effect of Powder Feeding Rate on Microstructure and Properties of Internal FeCoNiCrMo0.2 Coating by Laser Cladding |
| Received:May 27, 2024 Revised:October 24, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2025.05.015 |
| KeyWord:laser cladding high entropy alloys microstructure microhardness tribological behaviors electrochemical corrosion |
| Author | Institution |
| REN Xiangyu |
College of Mechanical Engineering, Xinjiang University, Urumqi , China |
| SUN Wenlei |
College of Mechanical Engineering, Xinjiang University, Urumqi , China |
| TIAN Shuang |
College of Mechanical Engineering, Xinjiang University, Urumqi , China |
| WANG Qiuyu |
Chongqing Pengshui Minzu Secondary School, Chongqing , China |
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| Abstract: |
| The work aims to improve the wear and corrosion resistance of tubular and inner wall parts (such as oil and gas transmission pipes) in petrochemical and other fields, and then extend the service life of parts. In this paper, high entropy alloy (HEA) coatings of FeCoNiCrMo0.2 were prepared by laser cladding at five different powder feeding rates on the inner surface of the 316L tube. Based on the macroscopic morphology, phase composition, grain structure, element distribution, hardness test, wear test and electrochemical corrosion characterization, the solid solution distribution, microstructure fineness, alloying element distribution, hardness and wear resistance of the five HEA coatings were evaluated, and the wear mechanism was analyzed. Finally, the corrosion resistance of HEA coatings were characterized by potentiodynamic polarization curve. The results showed that the five coatings were all composed of simple FCC phases, and the microstructure was mainly composed of columnar and cellular crystals. The microstructure of HEA coatings with 6 g/min and 18 g/min powder feeding rates were mainly composed of coarse columnar crystals, accompanied by a small amount of fine cellular crystals. The HEA coating at 6 g/min had the greatest dilution of 52% and had the greatest thermal impact on the substrate. Moreover, the HEA coating prepared at the powder feeding rate of 18 g/min contained obvious unmelted particles, and the forming quality was poor. The curves of coefficient of friction (COF) for 6, 9, 12, 15, 18 g/min were approximately stabilized at about 0.68, 0.65, 0.61, 0.58, and 0.63, respectively. The powder feeding rate of 15 g/min had a greater solid solution strengthening effect on the coating, and the solid solution was uniformly distributed. And the solidification of the coating at this time formed more fine cellular crystals, which reduced the elemental segregation during the solidification process and increased the hard phase content in the coating. In addition, the rate decreased the COF of the coating to 0.58, and its wear volume loss was 2.456 mg, which improved the tribological properties of the HEA coating. The wear mechanism of the five coatings included adhesive wear and abrasive wear. When the powder feeding rate was in the range of 12-15 g/min, the surface of the worn HEA coating was flat, and the wear depth was shallow. The wear morphology was characterized mainly by minor grooves caused by abrasive wear and a small amount of plastic deformation and spalling from adhesive wear. Moreover, in the electrochemical test, the self-corrosion current density of the HEA coatings reached a maximum of 1.02×10−6 A/cm2 at a powder feeding rate of 18 g/min. Compared with 6 g/min and 18 g/min, the Jcorr of the HEA coatings prepared at 9-15 g/min was reduced by 1-2 orders of magnitude, thus exhibiting excellent pitting resistance. The 15 g/min HEA coating had the lowest Jcorr value and the passivation interval with relatively large opening. The passivation film generated in-situ on the surface of the coating had more corrosion resistant substances, such as Cr2O3 and MoO2, which made it have relatively excellent corrosion resistance. Therefore, the FeCoNiCrMo0.2 coatings can significantly improve the tribological and electrochemical behaviors of the inner wall of 316L steel pipe, and achieve the purpose of strengthening the internal surface of the parts. Additionally, the powder feeding rate significantly affects the hardness and tribological properties of HEA coatings by influencing the phase composition, microstructure evolution and element distribution in the HEA coatings. The optimization of powder feeding rate helps to reduce the COF and wear loss of the HEA coating, and also helps to enhance the density of passivation film formed by the coating during corrosion, as well as increase the content of corrosion-resistant substances such as Cr2O3 and MoO2. |
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