Fabrication and Characterization of the Newly Developed Superalloys Based on Inconel 740

Abstract

The chemical composition of standard Inconel 740 superalloy was modified by changes in the Al/Ti ratio (0.7, 1.5, 3.4) and addition of Ta (2.0, 3.0, 4.0%). Remelted Inconel 740 (A0) and nine variants with various chemical compositions were fabricated by lost-wax casting. The microstructure, microsegregation, phase transformation temperatures, thermal expansion coefficients and hardness of the superalloys were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy, differential scanning calorimetry, dilatometry and Vickers measurements. Typical dendritic microstructure was revealed with microsegregation of the alloying elements. Segregation coefficient ki for Ti, Nb and Ta did not exceed unity, and so precipitates enriched mainly in these elements were found in interdendritic spaces. The Nb-rich blocky precipitates, MC carbides, MN nitrides, oxides, and fine γ’ was in all modified castings. Presence of other microstructural features, such as Ti-rich needles, eutectic γ-γ’ islands, small Al-rich and Cr-rich precipitates depended on the casting composition. The lowest solidus and liquidus temperatures were observed in superalloys with a high Al/Ti ratio. Consequently, in A7–A9 variants, the solidification range did not exceed 100 °C. In the A0 variant the difference between liquidus and solidus temperature was 138 °C. Hardness of all modified superalloys was at least 50% higher than for the remelted Inconel 740 (209 HV10).

Anisotropic Growth of the Primary Dendrite Arms in a Single‐Crystal Thin‐Walled Nickel‐Based Superalloy

“…Franke et al [ 4,5 ] and Grudzień‐Rakoczy et al [ 6 ] studied the influence of thermophysical properties, such as enthalpy of fusion, heat conductivity, and specific heat, on the solidification of nickel‐based superalloys. The temperature gradient at the solidification front and the solidification rate plays a major role in the formation of as‐cast microstructures.…”

Selected Properties of High Entropy Alloys Based on the AlFeMnNbNiTi System

“…One example includes materials based on the Co 1.5 CrFeNi 1.5 Ti 0.5 (Yeh et al 2014) system, which exhibits excellent high temperature properties and is considered as a competitive materials for nickel based alloys. Preparing elements made of refractory high entropy alloys using special foundering methods, such as casting into multilayer molds with ceramic shells, has an influence on the material behavior under high temperatures, broadening this application (Rakoczy et al 2019;Grudzień-Rakoczy et al 2020). Another example is high entropy steels based on the Fe-Mn-Al-Si-C system having excellent mechanical properties in low temperatures (below 0 • C) (Raabe et al 2015).…”

Investigations of the Usefulness of Dilatometric Methods in the Diagnostics of Combustion Engines

“…The multi-level nature of dilatometric analysis and the use of such methods for various analytical tasks related to the characteristics of materials have led tools based on this type of method to be successfully used in widely understood materials science [18][19][20][21][22][23][24]. Additionally, the ease of use and the mostly simple geometry of the sample make dilatometry a productive tool for thermophysical materials testing.…”