Grain growth and carbide precipitation in superalloy, UDIMET 520

Abstract

The results of an experimental study on the grain coarsening behavior, M 23 C 6 carbide precipitation, and secondary MC carbide precipitation kinetics in UDIMET 520 are presented. Primary MC carbides and M(C, N) carbonitrides strongly influence the grain growth, with their dissolution near 1190 ЊC and 1250 ЊC, respectively, resulting in two distinct grain coarsening temperatures (GCTs). M 23 C 6 carbides precipitate in the alloy over a wide range of temperatures varying between 600 ЊC and 1050 ЊC. A discrete M 23 C 6 grain boundary carbide morphology is observed at aging temperatures below 850 ЊC. Secondary MC carbides formed at temperatures ranging between 1100 ЊC and 1177 ЊC, in specimens in which primary MC dissolution had been obtained at solution treatment temperatures of 1190 ЊC to 1250 ЊC. A schematic time-temperature-transformation (TTT) diagram for understanding the microstructure and precipitation inter-relationships in UDIMET 520 alloy is also presented.

Creep crack growth in the absence of grain boundary precipitates in UDIMET 520

“…It is above (the intermediate and large grain size specimens) noteworthy that the solution treatment temperatures of 1190 the MC carbide solvus temperature. However, the CCGR ЊC, 1200 ЊC, and 1250 ЊC lie above the MC carbide solvus of specimens solution treated below the MC carbide soltemperature (1190 ЊC) of UDIMET 520, [10] whereas, the vus temperature was approximately 2.5 times lower than solution treatment temperatures of 1110 ЊC and 1135 ЊC lie those treated above this temperature. The reason for below this temperature.…”

“…Such primary MC carbides were formed during solidification and could be dissolved during solution treatment. [10] These MC particles were much less abundant on fracture surfaces E. Metallographic Observations of specimens solution treated at 1200 ЊC and 1250 ЊC than of those solution treated at 1110 ЊC and 1135 ЊC. In some Figure 14 shows an optical micrograph of the cross section of a CCG specimen, which had been solution treated at 1135 regions, the fractographic features indicated that crack arrest lines were present on many of the grain boundary facets (e.g., ЊC.…”

“…diameter stainless steel lead wires spot welded to the opposite corners of the CT specimens, as shown in 1250 ЊC, 2 h, WC Figure 1. The potential drop data acquisition (DA) system These heat treatments were designed on the basis of an was computer-controlled using a Quick-Basic language subearlier microstructural investigation [10] on UDIMET 520 to routine written during the course of this research program. obtain different grain sizes while precipitating certain…”

“…An aging treatment invariably produces an an aging treatment, such as M 23 C 6 carbides, will therefore form a thicker as well as a more continuous film with increasing grain size. [10] In addition to the complication of changes in grain boundary precipitate distribution, the grain size effect is further complicated by environmental effects, especially at high temperatures. The focus of this article is also placed on experimentally isolating the effect of grain size on CCGR from the effects of grain boundary precipitates and environment.…”

Modeling Grain Size and Strain Rate in Linear Friction Welded Waspaloy

“…For the OM studies on the parent disk material, after ultrasonic cleaning, the polished samples were immersion etched for 5 seconds in a solution composed of 60 mL HCl, 40 mL HNO 3 ,a n d 40 mL CH 3 COOH. [14] For the OM studies on the solution heat-treated, hot-compressed, and LFWed samples, the polished surfaces were electroetched in a solution composed of 10 g oxalic acid in 100 mL deionized water [15] with voltages ranging from 5.5 to 6.5 V at a current of 0.1 A for period ranging from 8 to 42 seconds, depending on the processing conditions. SEM studies for c¢ particles characterization were carried out using a high-resolution Hitachi S-4700 Field Emission Gun (FEG) SEM operated at an accelerating voltage of 15 kV in secondary electron (SE) mode.…”