Microstructure and mechanical properties of HSLA-100 steel repaired by laser metal deposition

HSLA-100 steel substrates with pre-machined trapezoidal grooves were repaired by laser metal deposition with HSLA-100 and nickel base alloy (GH3536) powders. The grooves can be restored and good metallurgical bonding was achieved. The microstructure and mechanical properties were analyzed. Results showed that the microstructure of the repaired zone was typical fine columnar crystals and dendrites. The main phase in the repaired zone (RZ) was martensite confirmed by transmission electron microscopy (TEM) and X-ray diffraction (XRD) results. No visible micro-pores or cracks was found under optical microscopy (OM). The micro-hardness of the RZ repaired with HSLA-100 steel powder was in the range of 240-350 HV while the sample repaired with GH3536 showed a relatively smooth micro-hardness distribution. The tensile properties were comparable to that of the substrate. The average absorbed impact energy at -40 degrees C of specimens repaired with HSLA-100 steel and GH3536 powder reached 29.6% and 88.5% that of the base material, respectively. The fracture mechanism was revealed by the SEM fracture analysis.