Realisation and characterisation of Al-Sn alloy layers deposited on mild steel by laser cladding

Abstract

Direct laser cladding of Al-Sn alloy on mild steel produces continuous brittle intermetallic FexAly layers at the interface resulting in weak bonding of the clad and the substrate. To overcome this problem, both Ni and Al were investigated as intermediate coatings. Although a Ni coating with a thickness of 70 μm was successful in eliminating the formation of continuous Al-Fe intermetallic compounds, the bonding at the Al alloy-Ni interface was not strong enough to survive a bending test. A pure Al coating was found to be a better barrier layer.In both cases the optimisation of processing parameters for Al alloy cladding was realised via microstructural screening and mechanical property testing including Vickers hardness, preliminary wearing and bending tests. Operating windows were established in terms of low dilution, freedom from cracks and porosity, coating-substrate bonding and chemical homogeneity. The results of a comparative study indicated that the laser clad layers showed superior wear resistance to the conventional alloy. The morphology of the rapid solidification clad was investigated by means of optical and electron microscopy. The alloying element distribution was analysed using electron probe microanalysis (EPMA). A simplified model based on the calculation of the clad/substrate interface temperature was developed to provide a guideline for choosing the processing parameters of successful cladding.Direct laser cladding of Al-Sn alloy on mild steel produces continuous brittle intermetallic FexAly layers at the interface resulting in weak bonding of the clad and the substrate. To overcome this problem, both Ni and Al were investigated as intermediate coatings. Although a Ni coating with a thickness of 70 μm was successful in eliminating the formation of continuous Al-Fe intermetallic compounds, the bonding at the Al alloy-Ni interface was not strong enough to survive a bending test. A pure Al coating was found to be a better barrier layer.In both cases the optimisation of processing parameters for Al alloy cladding was realised via microstructural screening and mechanical property testing including Vickers hardness, preliminary wearing and bending tests. Operating windows were established in terms of low dilution, freedom from cracks and porosity, coating-substrate bonding and chemical homogeneity. The results of a comparative study indicated that the laser clad layers showed superior wear resistance...