Hot cracking in cast alloy 718

Abstract

Hot cracking susceptibility of the Fe–Ni-based precipitation hardening cast superalloy Alloy 718 was studied by Varestraint weldability testing. The effect of two hot isostatic pressing (HIP) treatments commonly employed in the aerospace industry was investigated in reference to the as cast condition. It was found that the heat affected zone (HAZ) liquation cracking susceptibility increased for samples with pre-weld HIP treatments. The as cast condition disclosed the best response for liquation cracking followed by HIP-1120 (1120°C/4h (HIP) + 1050°C/1h and furnace cooling to 650°C/1h in vacuum + 950°C/1h) and HIP-1190 (1190°C/4h (HIP) + 870°C/10h and furnace cooling to 650°C/1h in vacuum + 950°C/1h). The amount of the secondary precipitates and base metal grain size was found to be important parameters influencing the cracking susceptibility. Regarding solidification cracking susceptibility, the three conditions appear to behave similarly.