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The coarsening and ageing hardening behaviors of γ’ particles in superalloy GH742 have been investigated by field emission scanning electron microscopy(FESEM),coarsening kinetics calculation and microhardness testing when ageing at 1 050,950 and 900 ℃ for different time.The cube of γ’ particle size and ageing time follows a linear law as predicted by LSW theory.The particle size distributions give better fit to the LSW theoretical distribution.The activation energy for γ’ coarsening is accurately determined to have 245.06±14.42 kJ/mol when considering the effect of temperature on the solution concentrations in matrix.Based on the activation energy,the coarsening kinetics of γ’ particle is predicted as r3t=7.35×1015Ce/Texp-(245 060±14 420)/RTt.The microhardness studies indicate that microhardness decreases rapidly with increasing the ageing temperature and it has a maximum value corresponding to a critical particle size beyond which the microhardness increase stalls with increasing the ageing time.
The coarsening and aging hardening behaviors of γ ’particles in superalloy GH742 have been investigated by field emission scanning electron microscopy (FESEM), coarsening kinetics calculation and microhardness testing when aging at 1 050,950 and 900 ° C for different time.The cube of γ’ particle size and ageing time follows a linear law as predicted by LSW theory. The particle size distributions give better fit to the LSW theoretical distribution. The activation energy for γ ’coarsening is determined to have 245.06 ± 14.42 kJ / mol when considering the effect of temperature on the solution concentrations in matrix. Based on the activation energy, the coarsening kinetics of γ ’particle is predicted as r3t = 7.35 × 1015 Ce / Texp- (245 060 ± 14 420) /RTt.The microhardness studies indicate that microhardness decreases rapidly with increasing the aging temperature and it has a maximum value corresponding to a critical particle size beyond which the microhardness increase stalls with increa sing the ageing time.