Effect of high pressure and high temperature on the microstructural evolution of a single crystal Ni-based superalloy

A quantitative metallographic assessment of the evolution of porosity during processing and creep in single crystal Ni-base super alloys

“…They have equiaxed shapes, Figures 7a, 8a. The fact that pores form during heat treatment is in line with previous work [8,14,20]. Previous work also suggests that a HIP treatment results in a decrease of porosity and an increase of creep life [20,16].…”

“…The fact that pores form during heat treatment is in line with previous work . Previous work also suggests that a HIP treatment results in a decrease of porosity and an increase of creep life . Creep life of single crystal Ni‐base superalloys is strongly affected by processing pores and their alignment along primary dendrites .…”

“…It is also well known, that in the absence of cast microporosity, pores can nucleate and grow during creep . The present work was motivated by recent work addressing porosity in single crystal Ni‐base superalloys . Pores can grow in single crystal Ni‐base superalloys, which creep under high temperature and low stress conditions .…”

“…This scatter in rupture behavior with different distributions of pores in the different creep specimens is explained. For heat treated LEK 94 porosity decreases when cast single crystal Ni‐base superalloys are subjected to HIP treatments, where a superimposed hydrostatic pressure represents the driving force for pore closure . In contrast, in the absence of external hydrostatic pressure, at temperatures above 1100 °C, pores grow during solution heat treatments.…”

On the Effect of Hot Isostatic Pressing on the Creep Life of a Single Crystal Superalloys

“…[3,4] This in turn stabilizes the g'-particles. [22] The effect is small and further work is required to find out whether this influence of HIP pressure on the g'-volume fraction is significant. All parameters describing the g/g'-microstructures prior to creep are summarized in Table 2.…”