Cooling precipitation and strengthening study in powder metallurgy superalloy Rene88DT

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 332; no. 1; pp. 318 - 329
• Main Authors: Mao, Jian, Chang, Keh-Minn, Yang, Wanhong, Furrer, David U, Ray, Koushik, Vaze, Suhas P
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.07.2002; Elsevier
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Hardening; Heat treatment; Materials science; Metals. Metallurgy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Powder metallurgy; Precipitation; Precipitation modeling; Quenching; Rene88DT; Solid-phase precipitation; Superalloy; Thermodynamic simulation; Superalloy; Hardening; Heat treatment; Precipitation; Thermodynamic simulation; Precipitation modeling; Powder metallurgy; Rene88DT; Quenching; Nickel base alloys; Cooling; Grain growth; Cooling rate; Digital simulation; Prime gamma phase; Experimental study; Interrupts; Superalloys; Tensile strength; Microstructure; Transition element alloys
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/S0921-5093(01)01758-0

The relationship of heat treat quench process, microstructure, and mechanical property in powder metallurgy superalloy Rene88DT had been experimentally studied to initiate the numerical simulation of γ′ precipitation and mechanical properties. Two novel cooling schemes were applied to study the cooling γ′ precipitation behavior. One was continuous cooling test carried out by linearly controlling cooling rate during quenching, which was to study the effect of cooling rate on the cooling γ′ precipitation and tensile strength. Another was interrupted cooling, which is performed by interrupting a continuous cooling test at the different intermediate temperatures. Interrupted cooling test is aimed at studying the development of γ′ precipitates during a quenching process. Strength response to the interrupt temperature was also investigated. Cooling γ′ precipitates are defined as those γ′ precipitates formed during the quenching after supersolvus solution. It was found that the size of the γ′ cooling precipitates increases with the decrease of cooling rate, which follows a power law with an exponential being about 0.47. The as-quenched strength increases with the increase of cooling rate. For a fixed cooling rate, the sizes of cooling γ′ precipitate increases as a linear function of interrupt temperature. However, a non-monotonic decrease in strength was observed as the interrupt temperature decreases. Aging treatment contributes to the final strength, with an increase of about 10%, which is believed to be related to the continuous growth of tiny γ′ during aging.