Effect of Melt Holding Time on γ‏'‏‎ Precipitates and Stress Rupture ‎Properties of Rene 80 Superalloy

The purpose of this investigation, is study the effect of melt holding time (3 , 20 min) in vacuum induction melting furnace (VIM) with alumina crucible on the amount of gases, γ' precipitates and stress rupture properties of Rene 80 superalloy. For this purpose, the amount of O, N gasses and chemical composition were analyzed. The microstructure was assessed by scanning electron microscopy (SEM) and stress rupture properties was performed at 980˚C. The results showed that with increasing the melt holding time from 3 to 20 min, γ' volume fraction reduced from 46 to 37% and also, oxygen level of the alloys increased from 79 to 165 ppm because of the alumina reduction. The morphology of γ' changed from semi-cubic to cubic one. The result of mechanical test showed that the stress-rupture life of samples reduced from 22.6 to 19 hours by increasing melt holding time because of reducing γ' volume fraction.