Effect of additional temperature fields on the mechanical properties of heterogeneous material transition layers in WAAM

• High-frequency induction heating technology was integrated into the Wire Arc Additive Manufacturing (WAAM) process. • The application of an additional thermal field modified the arc morphology during the cladding process and reduced internal defects in the transition layer. • The applied thermal field provided moderate cladding heat input, which facilitated the formation of a dense composite microstructure consisting of lath martensite and lower bainite in the transition layer, thereby enhancing its macrostructure. • The applied thermal field enhanced the overall mechanical performance of the transition layer by regulating the temperature gradient and cooling rate. To address the issues of non-uniform microstructure, high residual stress, and insufficient strength in the dissimilar material transition layer during WAAM repair of failed wind turbine gears, this study investigated the microstructure and mechanical properties of the 18CrMnNiMo-SMSX900A WAAM transition layer with and without an auxiliary induction temperature field, using ultrasonic testing, SEM, standard tensile tests, and friction and wear tests. The results demonstrate that with induction heating at 100°C, the moderate heat input facilitated the formation of a dense composite microstructure consisting of lath martensite and tempered martensite. Consequently, the ultrasonic reflection amplitude decreased to an equivalent value of 2.40, the microhardness distribution became uniform (315HV in the transition layer and 305HV in the cladding layer), and the fluctuation amplitude of the friction coefficient was only 0.02. Mechanically, the yield strength increased to 1130.6 MPa, although the elongation slightly decreased to 4.0%. In summary, induction heating at 100°C demonstrated optimal performance in optimizing the transition layer microstructure, controlling defects, stabilizing the process, and enhancing mechanical properties, achieving an excellent synergy among arc morphology, non-destructive quality, and in-service performance.