Hot tearing of nickel-based superalloys during directional solidification

✍ Scribed by J. Zhang; R.F. Singer

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 383 KB
• Volume: 50
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/s1359-6454(02)00042-3

✦ Synopsis

The propensity to form cracks during directional solidification was studied in two Ni-based superalloys, CM247LC and IN792 (with varying Ti and Hf contents). Quenching experiments were employed to freeze in the amount of remaining liquid during different stages in solidification. It was found that alloys with a strong tendency to hot tearingand, therefore, bad castability -display a strong change in volume fraction of remaining liquid with temperature at the final stages of solidification. A simple mathematical model shows that a strong change in the fraction of liquid results in high strains and strain rates during solidification, and this leads to crack formation and bad castability. The castability of IN792 can be improved significantly, and even be brought to CM247 levels, by control of Hf and Ti, as these elements affect the change of liquid fraction during the final stages of solidification.