A series of studies were undertaken to determine the optimum rejuvenation heat treatment of HAYNES 230 alloy and to examine its weld repairability. To simulate service exposure, samples of plate nominally 4.75 mm (0.187 in.) thick were exposed at temperatures of 760°C (1400°F) and 871°C (1600°F) for a period of 1500 hours. Room temperature tensile properties and stress-rupture properties at 927°C (1700°F)/62 Mpa (9 ksi) were determined and compared to the material in the unexposed condition. Rejuvenation heat treatments of exposed materials were performed at a temperature of 1177°C (2150°F) for times of 30 minutes to 3 hours followed by a rapid air cool. In all cases, the room temperature tensile and the stress-rupture properties were found to be comparable to those for the unexposed condition. Based on these data, a heat treatment time of 30 minutes was judged to be adequate. Plates representing the as-received, exposed, and exposed and rejuvenated conditions were gas tungsten arc welded (GTAW) using 230-W™ filler metal. Transverse tensile samples containing the weldments were tested at room temperature, and face and root weldment samples were bent around an approximate 2T radius. All of the results, including those for the exposed condition, were found to meet the requirements of Section IX of the ASME Boiler and Pressure Vessel Code.
Investigation of low stress rupture properties in Inconel-718 super alloy