Microstructure evolution, hardness response, and corrosion resistance of Inconel 625 weld overlay obtained by the ESSC process after post-welding heat treatments

Effect of the Shielding Gas and Heat Treatment in Inconel 625 Coatings Deposited by GMAW Process

“…Due to the high content of these elements, precipitates form at some points, which can be of the MC type ((Mo, Nb, Ti) C), Laves phase (Ni, Fe, Cr)2(Nb, Mo), phase γ" Ni3(Nb, Mo), and δ phase (Ni3Nb), as found by other authors in the literature [2,4,12]. According to Durandcharre [13], for welded coatings, the behavior of the solid/liquid interface is governed by a high-temperature gradient that quickly solidifies the molten metal. Dendritic solidification promotes a variation in the chemical composition between the center of the dendrites and its immediately adjacent region because the first regions to solidify reject the solute into the remaining liquid as solidification occurs (solute segregation).…”

“…According to Cieslak and Headley [24], the solidification of Inconel 625 begins with the formation of the austenitic γ phase in the form of dendrites and continues with the formation of second phases and carbides. The segregation of elements such as Nb, Si, and C into the interdendritic region makes solidification prone to forming secondary phases According to Durandcharre [13], for welded coatings, the behavior of the solid/liquid interface is governed by a high-temperature gradient that quickly solidifies the molten metal. Dendritic solidification promotes a variation in the chemical composition between the center of the dendrites and its immediately adjacent region because the first regions to solidify reject the solute into the remaining liquid as solidification occurs (solute segregation).…”

“…Different welding techniques have been used to produce Inconel overlays. Lowdilution coating processes such as cold metal transfer [9], laser [10,11], plasma transferred arc (PTA) [2,4], and gas tungsten arc welding (GTAW) [12] minimize the alteration of the chemical composition of the coating with elements from the substrate and reduce segregation, ensuring coatings with superior properties [13]. Alternatively, there is also the possibility of using gas metal arc welding (GMAW), which, on the one hand, leads to substantially greater dilution but, on the other hand, promotes greater production capacity [6,8].…”

“…A very influential factor in the microstructure of the Inconel deposits is the realization of the postweld heat treatment (PWHT). Some authors have investigated the influence of PWHT on different characteristics of Inconel 625 overlays [13,15,21]. The temperature and time used in PWHT can modify the microstructure and properties of the cladding.…”

“…The temperature and time used in PWHT can modify the microstructure and properties of the cladding. Heat treatments at around 1000 • C have been shown to decrease internal stresses by reducing the density of dislocations and, consequently, the coating hardness [10,13,15].…”