Influence of heat treatments on the mechanical properties and microstructure of a 50Cr-50Ni niobium containing alloy

Abstract

. Influence of heat treatments on the mechanical properties and microstructure of a 50Cr-50Ni niobium containing alloy. A heat resisting 50Cr-50Ni niobium-containing casting alloy, particularly developed for petrochemical plants was studied. The alloy combines high temperature strength with fuel ash corrosion resistance. However, during service, the exposure to high temperatures gives rise to precipitation of embrittling phases, strongly depleoting the material ductility. Therefore, studies on the thermal aging at 700 C were carried outo either in the as cast condition or after heat treatments at 1000, 1075, 1150 C. Alloy modifications were analyzed from a microstructural point of view and through hardness measurements, with the aim of relating them to other mechanical properties. It was found that the thermal treatments, providing a coarse precipitation, were effective in preventing excessive embrittlement levels to be reached.

Dissimilar welding of AISI 310 austenitic stainless steel to nickel-based alloy Inconel 657

“…It is known that Nb-rich phases have detrimental effect on weldability and weld mechanical properties such as ductility, fracture toughness, fatigue and creep rupture as well as consuming significant amounts of useful alloying elements (Caironi et al, 1993). Moreover, the presence of large amount of chromium in the alloy composition leads to a decrease in heat conduction.…”

Microstructural evolution and precipitation behavior in heat affected zone of Inconel 625 and AISI 904L dissimilar welds

“…On the other hand due to the presence of Mo, Cr and Ni rich in amount can enhance the precipitation of intermetallic phases including carbides and nitrides in these steels during prolonged exposure at elevated temperatures between 550 to 800°C [3]. Caironi et al [4] reported that during weld metal solidification, a hard brittle compound Nb-rich phase forms in regions of inter-dendritic due to the segregation of Nb, thereby deteriorate the mechanical properties. Dupont et al [5] investigated the bimetallic joints of two nickel alloys (Inconel 622 and Inconel 625) with AL-6XN super stainless steel and reported that the filler metal chemistry and the effect of welding processing parameters influences on the weldability and microstructure.…”

Influence of Artificial Aging on Microstructure and Mechanical Properties of Dissimilar Welds between 310 Stainless Steel and INCONEL 657

“…In the case of joint between 310 austenitic stainless steel (SS) and INCONEL* 657 superalloy in oil industries, failure of weldment under service can lead to serious dangers and vital determents. Formation of brittle and weak phases in the microstructure of weld and base metal of 310 SS-INCONEL 657 weldment may tremendously decrease impact toughness and yield-ultimate strength of the joint, [1,2] and therefore limit the choice of filler metal types. Although several types of filler metals, such as INCONEL 82, INCONEL 182, INCONEL 617, INCONEL A, INCONEL 52, INCONEL 152, and 310 SS, can be proposed for joining 310 austenitic SS to INCONEL 657, behavior and thermal stability of these weld metals in high temperatures and for long times should be clarified in order to be able to select the most appropriate filler materials.…”