Microstructural formation during hot isostatic pressing and heat treatment of EP741NP Ni-base superalloy, and the effect of the microstructure on mechanical properties

The structure and mechanical properties of highly-alloyed EP741NP superalloy in various conditions of HIP, isothermal forging and heat treatment were examined and tested. HIP`ing temperature has an influence on the structure and mechanical properties of the EP741NP superalloy. Microstructures and room and working temperature mechanical-properties of EP741NP superalloy after HIP carried out at the temperature of the complete dissolution of the {gamma}-phase, and temperatures in two- and single phase fields are shown. Problems concerning structure development in EP741NP superalloy mill products produced by PM technique followed by isothermal forging are discussed. Necklace structure and fine-grained microstructures developed in mill products produced by different techniques are examined. An advantage of the isothermal upsetting of extruded bars is shown. Parameters of the microstructure formed in the mill products produced by this technique and heat treated under optimum conditions ensuring high level of strength and high-temperature strength are studied.