Effect of final aging heat treatment on microstructure and mechanical properties of IN792

The IN792 casting superalloy is used in the manufacture of movable blades for gas turbines. Due to exposure to hard conditions, these parts are subjected to a variety of microstructural changes. The control of various stages of blade manufacturing includes casting, forging and heat treatment. In the meantime, controlling the heat treatment variables during the processing of nickel base superalloys is easier due to the ease of switching than other variables and the great influence on the microstructure and mechanical properties. Therefore,. The present research work is directed towards determining the effect of heat treatment`s parameters (time and temperatures of the final stage of aging treatment) on the hardness and microstructure properties of IN792 nickel-based superalloy. For this purpose, the 9 samples were annealed and then were solution heat treated, followed by a two-stage ageing process. In final stage of ageing, 3 different temperatures (870,845,800°C) in different ageing time (16, 24, 30 hours) have been chosen. The result revealed that in a constant time by increasing temperature, size of 𝜸́ phases increased while the amount of them decreased. The results was the same in a constant temperature and increasing time. The strength of these alloys is basically depends on a factors like volume fraction, size, growth rate, composition and well distribution of 𝜸́ precipitates. Homogeneous and uniform distribution of 𝜸́ precipitates was observed in a sample that was age treated at 845°C for 16 hours in which, the maximum hardness had been occurred. Also by increasing time and temperature, eutectic phases dissolved in matrix and carbides precipitate in the matrix and near boundaries which will improve mechanical properties.