Effect of De-coating and Filler Wire on the Microstructure and Mechanical Performance of Laser Welded PHS2000 Steels Coated with Al–Si Coating

In this present, the PHS2000 steels coated with Al–Si coating were carried out by laser de-coating and then laser welded with filler wire. Compared to direct laser welding, better welds were obtained after hot stamping. In the coated joint, the microstructure in the fusion zone consisted of ferrite and lath martensite, and Al segregation occurred near the fusion line. The hardness of lath martensite and ferrite was 547.6 and 275.0 HV_0.5, respectively. The tensile specimen fractured along the fusion line, and the ultimate tensile strength and total elongation were 1561.6 MPa and 1.33%, respectively. After removing the Al–Si coating and using filler wire, the microstructure in the fusion zone was all lath martensite, and the Al segregation was eliminated. The hardness of lath martensite increased to 577.2 HV_0.5. Meanwhile, the Al content decreased from 1.86% in ferrite to less than 0.06% in lath martensite. The ultimate tensile strength and total elongation increased to 1832.7 MPa and 6.35%, respectively. The failure of the joint was controlled by dimple-type fracture.