Thermoplastic behavior of Ni-Fe based superalloy HT700
[Objective]The purpose was to investigate thermoplastic behavior and its evolution rule with temperature of HT700.[Methods]Thermoplasticity of HT700 was tested by Gleeble-1500D thermo-mechanical simulator,zero strength and zero plasticity test was carried out,and microstructure and morphology near fracture were characterized.[Results]The research result showed that zero strength temperature of HT700 was 1 316℃,heating zero plasticity temperature was 1 270℃,cooling zero plasticity temperature was 1 250℃,zero plasticity temperature range was 20℃,and brittle temperature range was 66℃.[Conclusion]A smaller welding heat input and a faster cooling speed could be used to reduce residence time of heat affected zone and weld in the zero plasticity temperature range and the brittle temperature range,thereby preventing formation of hot cracks.Above 900℃,thermoplasticity of HT700 increased first and then decreased with the increasing temperature.At the zero plasticity temperature,liquidation of grain boundary occurred,and fracture mode was completely intergranular brittle fracture.Moreover,liquidation of grain boundary was related to liquidation of γ′and MC components at grain boundary.
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