Evolution in microstructure features and properties of Mo-containing Fe-Cr-Ni-B-Si composite coatings by laser cladding

Abstract

The nano-crystalline strengthening Fe-based amorphous composite coatings were successfully prepared by optical laser cladding technology. The influence of Mo content on the microstructure, mechanical, corrosion and tribological properties of Fe-Cr-Ni-B-Si composite coatings were studied. Results indicated that the phase composition and the relative content of amorphous changed obviously with the increases of Mo content. The microstructure could transform from coarse columnar into disorder amorphous matrix accompanying nano-precipitates of Fe-based composite coating with the appropriate Mo content, and while the excessive Mo element caused severe segregation of MoSi2 ceramic. The micro-hardness and plastic deformation resistance of the composite coatings dramatically improved due to the increased content of amorphous phases and in-situ nanocrystalline reinforcing, which had a favorable influence on the corrosion resistance and tribological property. The modified composite coating with the component of Fe41.4Cr16.2Mo10Ni5.4B1.5Si1.5 (atm.%) exhibited the most excellent mechanical properties (1102 HV), corrosion resistence (0.2216 μA/cm2) and wear resistance (2.96 × 10−6 mm3/N·m) among the three composite coatings. At this time, the modified coating had excellent resistance to pits corrosion and oxidation abrasive wear. However, the coating without Mo element occurred serious pits corrosion, abrasive and oxidation wear. The uneven distribution of MoSi2 brittle ceramic tended to the formation of microcracks and fatigue shedding for the composite coating with excessive Mo content.