Microstructure Development and Property Improvement in Mill Products Produced from Ingot Metallurgy and Powder Metallurgy Ni-Based Superalloys of the Same Chemical Composition

Abstract

Despite projected inroads from competing materials Ni-based superalloys remain the material of choice in the hot sections of advanced gas turbine engines. In this paper microstructural development and improvement of mechanical properties in mill products produced by ingot metallurgy (IM) and powder metallurgy (PM) techniques are discussed. Particular attention is given to approaches to improvement in ingot ductility. Thermomechanical treatment schemes used during forging of a complex-alloyed Ni-based superalloy are recommended. It is demonstrated that the PM technique used for production of this complex-alloyed superalloy is a promising approach. On the basis of the studies carried out the salient features of the structure of material produced both by both IM and PM techniques have been defined. The mechanical properties of two versions of an advanced Ni-base superalloy produced by IM and PM techniques are discussed. The best combination of mechanical properties are exhibited by a PM material with a necklace structure; and this latter structure is superior to a fine grained structure for IM product also.