Evolution of the microstructure, mechanical properties, and high-order modal characteristics of AISI 1045 steel subjected to a simulative environment of surface grinding burn

The thermal damage of AISI 1045 steel induced by laser surface treatment (LST), which is used to simulate the surface grinding burn, was comprehensively studied in this paper. By experimental investigation, a deep analysis was performed on the microstructure, hardness, and residual stress of the AISI 1045 steel specimens subjected to the LST process. Furthermore, the high-order modal characteristics of the AISI 1045 steel specimen were studied based on the high-frequency vibrator system. The experimental results reveal that the phase transformation-induced microstructure change, which can be reflected by hardness value, can be regarded as essential of the laser-induced thermal damage. The large tensile residual stress is another inevitable product that resulted from the LST process, which can be used to define the degree of surface grinding burn and belongs to the nondestructive classification technology for surface grinding burn by comparing with the microstructure-based classification technology. Moreover, the strain mode is more sensitive to the thermal damage of the specimen than the displacement mode and the resonant frequency, and the significant strain mode change of the specimen before and after the LST process will occur at higher vibration frequency. The findings confirm that the degree of surface grinding burn can be classified by using the X-ray diffraction (XRD) method, and the thermal damage in surface grinding process can be detected by using both the XRD method and the high-order strain mode method.