Microstructure and Mechanical Properties of NiCrMoV Steel Fabricated by Double-Electrode Gas Metal Arc Additive Manufacturing

Double-electrode gas metal arc additive manufacturing (GMA-AM), capable of reducing heat accumulation through bypass arc, was used to fabricate the thin-wall part of NiCrMoV high-strength low-alloy steel (HSLAS). The peak temperature and cooling time of thermal cycle in double-electrode GMA-AM compared with conventional GMA-AM decreased under the same conditions, which influenced the microstructure and properties of deposited metals. Microstructures of the deposited part were mainly bainite and martensite. As the deposition height increased, the martensite content decreased, and acicular ferrite microstructure was formed due to poor heat dissipation and multiple post-heatments. Introduction of bypass arc into double-electrode GMA-AM generated more martensite structure, which improved the hardness of the deposited part. Tensile strength and yield strength of the thin-wall part were both improved with bypass arc. The average ultimate tensile strength was 855 MPa, and the elongation was 19.5% through double-electrode GMA-AM.