Interface defect suppression and performance optimization of 45/316L/CuSn5 gradient layer prepared by laser cladding additive manufacturing

Aiming at the interface defect issue of 45/CuSn5 alloy cladding layer，this study proposes a method for suppressing interface defects and optimizing the performance of 45/316L/CuSn5 gradient cladding layer prepared by laser cladding additively using 316L as a transition layer. By systematically comparing the microstructure and element distribution of the interface between the 45/CuSn5 single cladding layer and the 45/316L/CuSn5 gradient cladding layer，the control mechanism of the 316L transition layer is revealed，and the properties of the substrate and gradient cladding layer are compared and studied. The results show that the gradient cladding layer forms a defect-free metallurgical bonding interface due to the introduction of 316L transition layer，and the interface exhibits obvious elemental interdiffusion. The high concentration gradient of Cr element effectively reduces the interface energy and suppresses crack initiation. The diffusion of Cu element into 316L promotes the formation of a Cu-Ni solid solution，while the transition from 316L to the CuSn5 surface cladding layer realizes a transition from austenite （γ-Fe） to an α-Cu solid solution. This crystallographic structure transition effectively suppresses the formation of interfacial brittle phases， thereby achieving interface defect suppression. In the friction and wear test under dry friction conditions with a load of 20 N and reciprocating linear motion for 30 min，the average friction coefficient of the gradient cladding layer is 0.1486，significantly lower than that of the substrate（0.4080）；the wear rate is 1.723 mm3·N-1·m-1，which is 30.21% lower than that of the substrate（2.469 mm3·N-1·m-1），achieving optimized wear resistance of the substrate. Electrochemical corrosion tests further show that in a 3.5%NaCl solution，the corrosion current density of the gradient cladding layer（3.105×10-6 A·cm-2）is one order of magnitude lower than that of the substrate（4.839×10-5 A·cm-2）， with the corrosion rate reduced by 93.58%， demonstrating significantly enhanced corrosion resistance.