Characteristics of Cobalt Powders as Laser Cladded Materials for Austenitic and Martensitic Steels

An attempt was made to create cladded coatings on austenitic and martensitic steels based on a cobalt alloy containing chromium and iron powders. The microhardness and tensile strength of the laser cladded surfaces were found to be high owing to the formation of crystallites of alpha-Cr solid solutions, alpha-Fe and alpha-Co3C phases. Experiments were carried out with the microstructure, surface roughness and wear resistance of coatings. Laser cladding was found to lead to greater resistance to fracture compared to uncoated substrates. The ultimate tensile strength of laser cladded martensitic steel was considered to be high due to the excellent adhesion at the interface between the cobalt coatings and the underlying steel surfaces. X-ray diffraction experiments revealed the chemical stability at high temperatures of one of the phases, alpha-Co3C. Hence, the resultant laser cladded surfaces can be used for a longer life cycle.