Hf lowers the incipient melting temperature of superalloy. As carbon content in Hf-bearing alloy decreases, the incipient melting temperature drops furthey. PD ingots have stronger tendency to incipient melting than H...Hf lowers the incipient melting temperature of superalloy. As carbon content in Hf-bearing alloy decreases, the incipient melting temperature drops furthey. PD ingots have stronger tendency to incipient melting than HRS ones. Even though in PD ingot, the sensitivities at both ends of the ingot are quite different. The melting of Ni_5Hf phase may be considered as one of the main factors affecting incipient melting. The more Ni_5Hf the alloy contains, the more serious the incipient melting becomes. The results of differential thermal analysis (DTA) have proved that the peak of 1135-1160℃ corresponds to the melting range or Ni_5Hf. By means of a pretreatment at 1150℃, 8h, Ni_5Hf phase can be eliminated in two ways: the reaction Ni_5Hf+γ(C)→MC_(2)+γ and solid solution, and therefore the final solid solution treatment can be carried out at 1260℃. This brings about a high homogenized structure and further increases the stress rupture properties of the alloy at 1040℃, 140 MPa.展开更多
The thin-wall effect of DZ25G, a directionally solidified (DS) superalloy, has been studied by ustng tubular investment cast thin-wall specimens with shape and wall thickness near the air-cooled hollow blades.The resu...The thin-wall effect of DZ25G, a directionally solidified (DS) superalloy, has been studied by ustng tubular investment cast thin-wall specimens with shape and wall thickness near the air-cooled hollow blades.The results show that the stress-rupture properties of the thin-wall specimens (thickness 0.8, 1.2 and 1.6 mm) are equivalent to the standard ones (diameter 5 mm),i.e., under the experimental conditions in this study the alloy DZ25G has insignificant thin-wall effect. It is apparent that the resulte are different from previous work. In the paper the reasons resulting in the difference were discussion in terms of the specimen manufacture process and thus microstructure feature.展开更多
文摘Hf lowers the incipient melting temperature of superalloy. As carbon content in Hf-bearing alloy decreases, the incipient melting temperature drops furthey. PD ingots have stronger tendency to incipient melting than HRS ones. Even though in PD ingot, the sensitivities at both ends of the ingot are quite different. The melting of Ni_5Hf phase may be considered as one of the main factors affecting incipient melting. The more Ni_5Hf the alloy contains, the more serious the incipient melting becomes. The results of differential thermal analysis (DTA) have proved that the peak of 1135-1160℃ corresponds to the melting range or Ni_5Hf. By means of a pretreatment at 1150℃, 8h, Ni_5Hf phase can be eliminated in two ways: the reaction Ni_5Hf+γ(C)→MC_(2)+γ and solid solution, and therefore the final solid solution treatment can be carried out at 1260℃. This brings about a high homogenized structure and further increases the stress rupture properties of the alloy at 1040℃, 140 MPa.
文摘The thin-wall effect of DZ25G, a directionally solidified (DS) superalloy, has been studied by ustng tubular investment cast thin-wall specimens with shape and wall thickness near the air-cooled hollow blades.The results show that the stress-rupture properties of the thin-wall specimens (thickness 0.8, 1.2 and 1.6 mm) are equivalent to the standard ones (diameter 5 mm),i.e., under the experimental conditions in this study the alloy DZ25G has insignificant thin-wall effect. It is apparent that the resulte are different from previous work. In the paper the reasons resulting in the difference were discussion in terms of the specimen manufacture process and thus microstructure feature.
