Laser cladding is an advanced surface modification technology, which can improve the surface properties such as wear resistance, corrosion resistance, fatigue wear resistance, oxidation resistance of different powder materials without changing the substrates. The work aims to improve the wear and corrosion resistance of ER8 high-speed wheel steel to increase the service life of wheels. In order to compare the wear resistance and corrosion resistance of different powder coatings and substrates in acid rain solution, the laser cladding technology was used to improve the performance of ER8 high-speed wheel steel and improve the service life of wheels, so as to cope with the bad service environment of train wheels. The wear and corrosion resistance of Fe-based alloy coating and Co-based alloy coating in simulated acid rain solution were compared and analyzed. The wheel steel was cut into sample blocks of 30 mm×20 mm×5 mm, and the circular gap with width of 10 mm and maximum depth of 2 mm was removed in the middle part of the matrix material sample. The substrate was polished smooth and cleaned with sandpaper. Under the laser power of 1 600 W, spot diameter of 4 mm, scanning rate of 7.5 mm/s and lap rate of 50%. Fe-based and Co-based alloy coatings were prepared by Laserline LDF6000-100 laser on the substrate surface. Then, the microstructure morphology, phase type and nano hardness of the coating were analyzed by SEM, XRD and nano indentation apparatus. With the help of MFT-EC4000 reciprocating electrochemical friction and wear tester, the samples were placed in acid rain solution for friction and wear test and electrochemical corrosion test. According to the results of uniform coating on the surface of compact structure, good metallurgical combination, Fe-based and Co-based alloy coating respectively presented "cellular" and "honeycomb". There was no obvious defects such as holes and cracks. The coating hardness is significantly higher than that of matrix hardness. The solid solution and carbide formation made Fe-based coating hardness more outstanding. The HV hardness was up to 714.4 on average. The substrate had light wear at low frequency (1 Hz) and, severe spalling, pitting corrosion at high frequency (2 Hz, 4 Hz). The wear mechanisms were mainly adhesion wear, oxidative wear and abrasive wear. There was no obvious corrosion and peeling phenomenon in the coating wear area. At high frequency, the wear rate of Fe-based coating and Co-based coating decreased by 6.10×10–5 mm3/(N·m) and 39.85×10–5 mm3/(N·m), respectively. At the same time, the impedance value of the coating in acid rain solution was significantly increased, and the polarization curve test results showed that the self-corrosion potential of Fe-based coating, Co-based coating and substrate was –0.522 V, –0.381 V and –0.603 V, respectively. The corrosion densities were 3.916 μA/cm2, 0.312 μA/cm2 and 5.483 μA/cm2, respectively. The wear resistance and corrosion resistance of the repaired wheel steel samples are improved to varying degrees. In comparison, the wear resistance of the Fe-based alloy coating is more excellent. The corrosion resistance of Co-based alloy coating is slightly stronger than that of Fe base coating. © 2023, Chongqing Wujiu Periodicals Press. All rights reserved.
