Correlation Between Cooling Rate and γ ' Precipitate Size in Rene 95 Alloy Fabricated Through a Powder Metallurgy Process

We investigated the correlation between the cooling rate and the cooling γ ′ ( γ ′ c ) precipitate size in a Rene 95 alloy. The alloy powders were prepared through an electrode induction gas atomization, and the powders were consolidated by hot isostatic pressing. The solution heat treatment was performed using a gas-quenching furnace, which can control the cooling rate via the gas pressure. The samples were annealed at a sub-solvus temperature of 1135°C, and argon was used as the quenching gas. Experiments were carried out under four conditions with quenching gas pressures of 1, 2, 3, and 9 bar. At these pressures, the cooling rate increased to 114.5°C/min, 157.1°C/min, 201.1°C/min, and 282.9°C/min, respectively. The average size of the γ ′ c at the cooling rate of 114.5°C/min was 133 nm, and it decreased to 88 nm at 282.9°C/min. The power law relation was used to derive the equation for predicting the γ ′ c size concerning the cooling rate, while the data obtained from this study and the results from a previous study were used to fit the power law equation. From the analysis, parameters of A and n were determined to 179.4 and 0.493, respectively.