Investigation Of Thermal Fatigue Mechanism And High-temperature Bending Strength Of W-Cu/1Cr18Ni9 Brazed Joint With Ni-based Filler Metal

This paper studied the effect of different holding time on thermal fatigue property of NiCrSiB brazed joint firstly.Subsequently,the thermal fatigue of NiMnSiCu-Zr brazed joint also was investigated.Evaluating of thermal fatigue properties of W-Cu/1Cr18Ni9 brazed joints by measuring the length of fatigue crack.The high-temperature mechanical properties of NiCrSiB brazed joint and NiMnSiCu-Zr brazed joint were further explored.This paper explores a thermal fatigue test process,which suitable for W-Cu/1Cr18Ni9brazd joint sample.Its process parameters are the upper limit temperature?_max=400?,lower limit temperature?_min=20?,heating time t₁=420s and cooling time t₂=30s.With the increment of fatigue cycles,thermal fatigue damage of W-Cu/1Cr18Ni9brazed joint became increasingly serious,and the length of fatigue crack increases gradually.Moreover,the mechanical properties of brazed joint was also decreasing with the increment of fatigue cycles,but the mechanical properties damage is limited.The holding time 10min NiCrSiB brazed joint is mainly brittle fracture characteristic.With the brazing holding time increment,the fracture characteristic of NiCrSiB brazed joint from brittle fracture to mixed ductile-brittle fracture.However,a small amount fracture location in the brazing seam changed from the cleavage surface to the dimples of holding time 60min NiCrSiB brazed joint,it is mainly mixed ductile-brittle fracture characteristic.The NiMnSiCu-Zr brazed joint is mainly ductile fracture characteristics.Thermal fatigue cycles has little effect on the fracture characteristics of the brazed joint.Fatigue crack initionation was appeared in the holding time 10min NiCrSiB brazed joint firstly,while fatigue crack propagation rate of holding time 60min brazed joint is greater than the others NiCrSiB brazed joint with the increment of fatigue cycles.Fatigue crack propagation rate decreases with the increment of holding time when the fatigue crack is extended to the defect-free zone.Meanwhile,NiMnSiCu-Zr brazed joint is of excellent performance.With the increment of temperature,NiCrSiB brazed joint mechanical properties first stable,then increase.The holding time 60 min brazed joint fracture location is mainly the interface of W-Cu and brazing seam at 100?³00?,it is mainly mixed ductile-brittle fracture characteristic.However,with the increment of temperature the fracture location was changed.The fracture location was on the base material side of W-Cu,which was away from the brazing seam.NiMnSiCu-Zr brazed joint mechanical properties was decreases with the increase of temperature.The brazed joint is mainly ductile fracture characterized.