The Oxidation Characteristics of the γ–γ′ Tie-Line Alloys of a Nickel-Base Superalloy

Abstract

A novel family of bond coats designed to be in EQuilibrium with their nickel-base superalloy substrates has been developed. These coatings have hence been termed 'EQ coatings'. The first step taken for EQ coating development was to examine the -0 tie-lines of several superalloys. In these superalloys, and 0 are in equilibrium with each other, and elemental activities are thus equal in these two phases. With equal activities, there will be no chemical potential differences between the two phases, and there is thus no driving force for diffusion. Applying ; 0 , or a combination of both as bond coat candidates will ensure that no inter-diffusion zone (IDZ) will form. This is desirable, as IDZ causes gross local mechanical property degradation.In this paper, the 0 volume fraction was varied from 0 to 100% at 25% intervals along the -0 tie-line of a nickel-base single-crystal alloy, TMS-82+. Cyclic and isothermal oxidation tests were conducted at 1100 C in ambient atmosphere. The resultant oxide structures, and the element concentration profiles from around the oxide/substrate interface, through the depletion zone, into the sound substrate, were analyzed by SEM/EDX.All samples started with the same element activities; hence, at the onset of oxidation, all samples were expected to form the same oxide structure. However, experiments showed that the specimens formed vastly different oxide structures, and that 0 had the best resistance against high temperature oxidation.

The Role of the γ′ Precipitate Dispersion in Forming a Protective Scale on Ni-Based Superalloys at 750 °C

“…They have been optimised for high creep strength and microstructural stability and, with *6 wt% Al and *3 wt% Cr, would be expected to have only a borderline capacity to form and maintain a protective alumina layer [1]. Reported work on the oxidation of these types of alloys tends to be focussed on behaviour at high temperatures, C1,000°C [2][3][4][5][6][7]. At these temperatures, under thermal cycling conditions, non-protective oxides form together with sub-surface oxidation.…”

Intermediate Temperature Internal Oxidation in Fourth Generation Ru-bearing Single-Crystal Nickel-base Superalloys

“…TCPs break up the rafted microstructure [2] and deplete the matrix of solid-solution strengtheners [3]. Although the effect of Ru on ''reverse partitioning'' is the subject of debate, its effect on oxidation performance has been reported only at higher temperatures, typically C1,000°C [4][5][6][7][8][9]. At these temperatures, non-protective oxides form together with sub-surface oxidation.…”

Sandwich‐Like Cu/Al/Cu Composites Fabricated by Cryorolling

“…Laminated metal composites are composed of alternating layers of metals or alloys, bonding together at their interface, which have gained extensive attention because of their advantages such as improved fracture toughness, impact behavior, corrosion, wear, and damping capacity, and have many applications in industrial sectors such as aerospace, automotive, and household applications . To fabricate laminated metal composites, researchers have developed many methods such as hot roll bonding, cold roll bonding, cryogenic roll bonding, accumulative roll bonding, cross‐accumulative roll bonding, and explosive welding . Roll bonding is the most widely used method to process all kinds of metallic composites.…”