Influence of solutioning on microstructure and hardness of hot isostatically pressed Astroloy

• Published in: Journal of alloys and compounds 2017-11, Vol.723, p.1082-1090
• Main Authors: Bassini, E., Marchese, G., Cattano, G., Lombardi, M., Biamino, S., Ugues, D., Vallillo, G., Picqué, B.
• Format: Article
• Language: English
• Subjects: Astroloy; Astroloy (trademark); Coarsening; Cooling rate; Grain boundaries; Hardness; Heat treating; High temperature; High-temperature alloys; Hot isostatic pressing; Microstructure; Net-shape; Powder metallurgy; Solutioning heat treatment
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2017.06.332

The influence of solutioning treatment on Astroloy fabricated via Hot Isostatic Pressing has been investigated. Both sub- and super-solvus solutioning treatments were performed, gradually increasing the test temperature from 1115 to 1200 °C in order to cross the ɣ′ solvus. The effects of the solutioning temperature and of the following cooling step were studied in terms of amount of reinforcing precipitate ɣ′, of γ-grain coarsening and of alloy hardness. Grain boundaries morphology was observed to be clearly modified by the solutioning conditions moving from the “smooth” to the “serrated” type. It was also possible to draw a clear correlation between cooling rates and Astroloy hardness. [Display omitted] •1115 and 1160 °C resulted best sub- and super-solvus temperature respectively.•Slow cooling causes coarse and irregular ɣ′ precipitation, which is detrimental.•The hardness is affected by solution temperature but more markedly by cooling rates.•Cooling rates between 50 and 70 °C/min result to be the optimal compromise.•Correct cooling rate allows to retain serrated grain boundaries.