Effect of laser scanning velocity on the microstructure and wear resistance of laser nitride h-BN self-lubricating

Abstract

To solve the problem of self-lubricating decomposition during fabricating coating on the surface of IN718, laser nitriding was applied. The impacts of different velocities on microstructure and wear resistance of the self-lubricating coating were investigated. The results show the fabrication of a crack-free composite coating, incorporating the in situ synthesis of self-lubricating phase h-BN by laser nitriding. Additionally, as the laser scanning velocity increased from 3 mm·s−1 and 7 mm·s−1 to 12 mm·s−1, the distribution of the self-lubricating phase h-BN in the coating shifted, transitioning from a uniform distribution throughout the coating to primarily accumulating in the upper region of the coating. The hardness of the coating at different speeds is similar. The average hardness of coatings is around 1.2 time that of the substrate. At room temperature, the wear rate of velocity 7 mm·s−1 is 0.94 and 0.81 of that velocity 12 mm·s−1 and 3 mm·s−1. At high temperatures, the velocity 3 mm·s−1 has the best wear performance. The wear rate of velocity 3 mm·s−1 at 500°C is 0.3 and 0.4 times of 200°C and 300°C. The wear mechanism is mainly abrasive wear at room temperature. At 200°C and 300°C, the wear mechanism is mainly abrasive wear and oxidation wear and mainly oxidation wear at 500°C.