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Microstructure control of HIPed inconel 718 alloy

N.El-Bagoury, M.Ramadan, M.Waly, K.Ogi

The influence of solution and aging heat treatment processes on microstructure of Hipped Inconel 718 (IN718) alloy has been investigated. Conventional solution treatment (CST) at 1273Kfor 1h precipitates a thin filmof ä phase at the grain boundaries of matrix.However, after solution at 1440K for 3h long (modified solution), the precipitates of  phase entirely eradicate fromthemicrostructure. Small colonies of needle-like  phase start to appear with aging at 1023K for 4h, afterCST. Prolonging the aging time to 50h, these colonies enlarge in size and spread in the matrix. XRD and TEM observations were used to identify the precipitation of hard  and  phases. The changing in hardness measurements was evidence about the precipitation of these hard phases. CST has higher rate to increase in hardness with aging time comparing to modified solution specimens.