Laser Cladding Fe-Base Alloy Coatings Structure for Marine Hydraulic Column

Herein, a novel laser cladding process of hydraulic column based on Fe-based alloy is presented. The microstructure and properties of 27SiMn steel was used as the base material for the pillar of mining support after laser cladding overlapping and to improve its surface properties. The macroscopic appearance and microstructure of the samples were characterized by optical microscope, scanning electron microscope and EDS dispersive spectrometer. The hardness of the coating cross-section was measured with micro-hardness tester which concluded that the microstructure of single pass cladding layer is composed of columnar crystal and equiaxed crystal. Moreover, the microstructure of single-pass cladding layer is composed of columnar and equiaxed grains. After lapping, columnar grains become coarser and show various dendritic growth patterns and the boundary between the inner and outer layers of the cladding layer in the overlap zone was obvious which is related to the preheating and secondary thermal effect of the substrate. Moreover, the difference of microstructure between the inner and outer layers is obvious and the size of equiaxed grains in the inner layer of the cladding layer boundary is related to the thickness of the cladding layer attached to the surface. The inter-dendritic segregation exists in the overlap cladding layer and the average hardness of the cladding layer reaches to 668.1 HV, which is three times higher than that of the substrate.