Microstructure and mechanical properties of laser melting deposited 1Cr12Ni2WMoVNb steel

1Cr12Ni2WMoVNb martensitic stainless steel was fabricated by laser melting deposition (LMD) process. Microstructure was characterized by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Vickers microhardness and room-temperature tensile properties were evaluated as well. Results indicate that the laser deposited steel has a fine well-aligned dendritic structure with a primary dendrite arm spacing of approximately 13 mu m. In the interdendritic regions there are fine phases which have a core-shell structure consisting of ferrite and many carbide particles. During the LMD process, the depositing layer has a reheating treatment on the top un-melted region of the previous layer, resulting in the formation of interlayer heat-affected zone (ILHAZ). Due to the existence of the ILHAZ, microstructure and microhardness of the laser deposited steel are non-uniform. The adjacent layers have the same crystallographic orientation, revealing that epitaxial growth of the depositing layer on the previous layer is not interrupted by the ILHAZ. Room-temperature ultimate tensile strength of the laser deposited steel reaches 1223 MPa, which is comparable to the wrought bar. (C) 2010 Elsevier B.V. All rights reserved.