Fatigue behavior of welded joint spray fused by nickel-base alloy powder

Modification of spray fusing (MSF), which is a new method, was used to improve the fatigue strength of welded joints. Cruciform welded joint of Q235B steel was processed by MSF with nickel-base alloy powder of Ni60A and Ni25A. The bonding layer between coating and weld was studied by optical microscopy, scanning electron microscopy (SEM) and energy spectrum analysis. The results show that flame spray fusing can produce a coating layer with finer microstructure, lower impurities content, less air hole and higher bonding strength. Stress concentration at weld toe was significantly reduced due to smooth coating of high curvature after MSF. High cycle fatigue test results indicate that fatigue strength of welded joint spray fused by Ni60A is higher than that of welded joint spray fused by Ni25A owing to the good effect of MSF. Low cycle fatigue test results show that fatigue life of welded joint spray fused by Ni25A dose not affected by the poor effect of MSF compared with welded joint spray fused by Ni60A.