超音频脉冲电流叠加对高氮钢 GMA 增材制造组织性能的影响

The nitrogen loss and the reduction in mechanical properties of high nitrogen steel may happen during additive manufacturing. The conventional pulsed gas metal arc(P-GMA)and P-GMA superimposed with ultrasonic frequency pulse current at the peak stage of pulse current are used to conduct the arc additive manufacturing experiments of high-nitrogen steel,and the single-pass multi-layer high nitrogen steel straight wall bodies under different processing parameters are prepared. The influence of ultrasonic frequency pulse current superposition on the solidification mode,microstructure evolution and mechanical properties of arc additive manufactured high-nitrogen steel parts were studied. Due to the nitrogen loss of arc additive manufactured high-nitrogen steel parts,the solidification mode of metal molten pool of high-nitrogen steel changes from A to FA in different arc additive manufacturing modes. Compared with the conventional P-GMA,the high-frequency ultrasonic effect generated by ultrasonic frequency pulse current can increase the diffusion of nitrogen elements,promote the austenite phase transformation,and limit the growth of ferrite dendrites. After comparative analysis,the impact of ultrasonic frequency pulse current on the Y-axis direction of ferrite dendrites is greater than that on the Z-axis direction,the impact of it on the mechanical properties in the Y-axis direction is also greater than that in the Z-axis direction. When the frequency is 60 kHz,the tensile strength in the Y-axis direction is increased by 9. 9%,and the yield strength is increased by 15. 9%.