Effect of Molybdenum on the Microstructures and Properties of Stainless Steel Coatings by Laser Cladding

Stainless steel powders with different molybdenum (Mo) contents were deposited on the substrate surface of 45 steel using a 6 kW fiber laser. The microstructure, phase, microhardness, wear properties, and corrosion resistance of coatings with different Mo contents were studied by scanning electron microscopy (SEM), electron probe microanalyzer (EPMA), X-ray diffraction (XRD), microhardness tester, wear tester, and electrochemical techniques. The results show that good metallurgical bonding was achieved between the stainless steel coating and the substrate. The amount of M7(C, B)3 type borocarbide decreases and that of M2B and M23(C, B)6 type borocarbides increases with the increase of Mo content in the coatings. The amount of martensite decreases, while the amount of ferrite gradually increases with the increase of Mo content. When the Mo content is 4.0 wt. %, Mo2C phase appears in the coating. The microstructure of the coating containing Mo is finer than that of the Mo-free coating. The microhardness decreases and the wear resistance of the coating gradually improves with the increase of Mo content. The wear resistance of the 6.0 wt. % Mo coating is about 3.7 times that of the Mo-free coating. With the increase of Mo content, the corrosion resistance of the coating firstly increases and then decreases. When the Mo content is 2.0 wt. %, the coating has the best corrosion resistance.