The Effects of Carbon Content on the Microstructure and 650°C Tensile Properties of Incoloy 901 Superalloy

Abstract

The microstructure and tensile properties of Incoloy 901 superalloy with various contents of carbon (0.02-0.09 wt%) were studied and a proper amount of carbon was determined to achieve good tensile properties at 650°C. The alloys were produced by vacuum induction melting and electro-slag refining (VIM þ ESR) process and then they were hot rolled. After heat treatment, microstructures and 650°C tensile properties of specimens were investigated. Phase analysis with X-ray diffraction (XRD) indicated that Incoloy 901 contained Metallic carbides (MC)-type carbide enriched with Ti and Mo. With increasing carbon content from 0.02 to 0.09 wt%, carbide area fraction increased from 0.73% to 1.2%. Also, increasing of carbon content gave rise to higher amounts of carbide sizes. Using XRD patterns, the lattice parameters of γ and γ′ phases were determined and the results showed that, with increase of carbon content, the lattice parameters of γ and γ′ phases decreased and the mismatch between them increased from 0.119% for alloy containing 0.02 wt% to 0.167% for alloy containing 0.09 wt% C. The maximum strength of the alloy was obtained at 0.05 wt% carbon and ductility decreased slightly with increasing carbon.

Nanoindentation size effects of mechanical and creep performance in Ni-based superalloy

“…Figure 2 demonstrates SEM micrograph of carbides which are situated in grains and at grain boundaries in alloy 901. The EDS spectra from the observed carbides indicate that elements Mo and Ti are present in carbides and (Ti, Mo)C carbide was also reported in the same alloy [23] and other superalloys such as U-500 and Rene 77 [12]. Annealing twinnings, one of the microstructural features of this alloy, are also illustrated in Figure 2.…”

“…It is worth noting that γ′ precipitates could not be detected at the magnifications of SEM, since this family of alloys exhibit an ultrafine precipitate in nanometric size in face-centered cubic (FCC) matrix [13]. According to previous study [23], the increase of carbon content of 901 can lead to a higher amount of carbide sizes, meanwhile it can give slight rise to the mismatch between γ and γ′ phases, which are beneficial to the alloy in the first place, and then big blocky carbides become crack initiation sites, because of the incoherent interface of MC and matrix. The average grain size (equivalent circular diameter) is around 100 µm and most precipitates’ size is several micrometers, Figure 2, while the maximum indenting depth is set to be 200 to 2000 nm and the corresponding maximum indentation size (equivalent circular diameter) is between 2 and 10 µm as shown in Figure 1.…”

Dependence of titanium carbide stability at elevated temperatures on Co content in Co(Ni)-25Cr-1.6Ti-0.4C superalloys

“…Titanium is a light metallic element, used for example for aeronautic components possibly exposed to moderate and even high temperatures (as aluminides [1,2]) or in in biomedical applications [5,6]. It is a strong carbide-former element, as well as a nitride-former one, this allowing it to be involved in bulk materials as well as in coatings, to improve the room or high temperature mechanical behaviour of various components [7][8][9]. In these applications titanium is often associated to other MC-former elements as Nb or W, this leading to multimetallic MC carbides not necessarily very stable at high temperature [10][11][12].…”