Abstract: Effects of solution treatment on the strength, toughness and residual stress of the repaired surfacing layer were analyzed by observing the microstructure, testing the mechanical properties and testing the residual stress of the specimens before and after solution treatment. The results show that before the solution treatment, the grains in the clad zone are large and uneven, the grains in the heat affected zone are thick, and the substrate zone consists of ferrite and pearlite. After solution treatment at 900 ℃ for 3.5 h, the proportion of ferrite in the substrate zone increases and the distribution is more uniform, the coarse grains in the heat affected zone and the clad zone disappear, the grains are refined, and the grain boundary characteristics and grain structure are significantly improved. Solution treatment significantly makes the tensile strength of the surfacing layer incrense from 810 MPa to 925 MPa, with an increase of about 14%. In addition, the solution treatment results in a general decrease in hardness, from 154 HV to 143 HV for the substrate, from 238 HV to 228 HV for the heat affected zone, from 243 HV to 226 HV for the clad layer, and at the same time, the peak residual compressive stress is reduced from 232 MPa to 182 MPa, with a reduction of 21.6%. These changes indicate that solution treatment improves the plastic deformation ability and overall performance of the material by reducing defects, improving grain uniformity and eliminating residual stress.

Key words: inner wall of axle box, repaired surfacing layer, solution treatment, mechanical properties, residual stress