Optimization of the Hot Isostatic Pressing of Ni-base superalloys and titanium alloys using principles of modern physical metallurgy and materials characterization

Hot Isostatic Pressing (HIP) offers a number of advantages for the (near-) net shaped processing of components for industrial applications. Despite these various advantages, there are a number of application-limiting problems associated with this processing route that have been the subject of study over many decades. In this paper, the successful application of aspects of physical metallurgy to the problems associated with prior particle boundaries (ppb) in Ni-base superalloys, and the HIP’ing of Ti alloys to avoid complications associated with dwell-fatigue. Regarding the first of these, i.e., ppb’s in HIP’d Ni-base superalloys, the nature and distribution of second phase particles have been characterized using recent developments in electron detection technology in scanning electron microscopy. This has permitted the determination of the coincidence of particles and high angle grain boundaries as a function of powder type. From this characterization, the ways to minimize the influence of ppb’s may be deduced and these will be discussed. In the second example, powders of a recently developed Ti-Al-V-Fe alloy have been HIP’d. Microstructural characterization reveals an absence of beta-flecks and the presence of a rather uniform and refined microstructure. The results of mechanical property determinations will be presented and the resulting microstructure/property interrelationships will be discussed.