Microstructure and Mechanical Properties of Laser Clad18Ni300 Coatings with La2O3 Addition on ZL205A Aluminum Alloy

The preparation of Fe-based wear-resistant coating by high-speed laser cladding method can well solve the problem of poor wear resistance of aluminum alloy surface. However, due to the large expansion coefficient difference of Fe and Al, the Fe-based laser cladding layer on the Al surface often has cracks, poor molding morphology, and poor mechanical properties. In this work, La₂O₃ is added as an additive in order to improve the morphology and mechanical properties of Fe-based laser cladding layer on the surface of Al alloy. High-speed laser cladding technology was used to prepare the coating of 18Ni300 + XLa₂O₃(X = 0.5, 1, 1.5, 2 wt %) on ZL205A aluminum alloy. The morphology, microstructure, hardness, wear resistance and heat shock resistance of the cladding layer were studied. The morphology and crack characteristics of the fusion zone were observed by scanning electron microscopy. Under the present test conditions, the addition of La₂O₃ improved the forming morphology, refined the microstructure of the cladding, and significantly improved the mechanical properties of the cladding. The optimal addition of La₂O₃ with the best properties was 1.5 wt % which provided: flat cladding surface, absence of internal cracks, refined grain size, improved wear resistance and thermal shock resistance, 47% higher hardness when compared to 18Ni300.