Effect of Reversion Heat treatment on Duplex Stainless Steels

The thermal aging embrittlement of duplex stainless steels is one of the key material property degradation that would limit their industrial applicability. In this investigation, we study the effect of reversion heat treatment on the mechanical properties of the thermally embrittled steels. The samples were solutionized, aged, reversion heat treated and re-aged. The tensile strength of the aged sample had increased with respect to the solutionized condition because in aged condition, the ferrite phase was spinodally decomposed into iron rich alpha (a) and chromium rich alpha-prime (a') precipitates and also the chromium nitride precipitates was found along with these precipitates. The 60 minutes reversion heat treated samples showed a maximum recovery in tensile strength of upto 92% with respect to the solutionized condition because the temperature of 550 °C is above the (a + a') miscibility gap, the ferritic phase was homogenized again. In other words, Ferich a and Cr-rich a' prime precipitates which were formed during ageing become thermodynamically unstable and dissolve inside the ferritic phase.