Research on fatigue behavior of welded joint spraying fused by low transformation temperature alloy powder

• The new prolong life method of MSF about welded joint was put forward.
• The low transformation temperature alloy powder was applied to the method of MSF.
• The fatigue strength of LTT-joint increases by 74.07%.

Modification of spraying fused (MSF) of plasma arc as heat source was used to improve the fatigue performance of welded joint, which both fundamentally reduced stress concentration at weld toe and achieved metallurgical bond between spraying fused coating and welding. The low transformation temperature alloy powder was applied to the method of MSF. After spraying fusion, especially spraying fused joint by low transformation temperature alloy powder, the distribution of residual stress is more difficult to be obtained. Finite element (FE) simulation as an important tool was used to determine the stress field and temperature field of spraying fused joint. Simulated results show that as-welded joint and welded joint spraying fused by conventional nickel base alloy powder (Conventional-joint) present tensile stress. The stress of welded joint spraying fused by low transformation temperature alloy powder (LTT-joint) is compressive stress. Fatigue test results indicated that under the condition of 2 × 106 cycles, the fatigue strength of as-welded joint is 135 MPa, while that of Conventional-joint and LTT-joint is 218 MPa and 235 MPa, respectively. The fatigue strength of Conventional-joint increases by 61.48%, and fatigue strength of LTT-joint increases by 74.07%.