浇注温度对K417G合金组织及力学性能的影响

Effect of Pouring Temperature on Microstructure and Mechanical Properties of K417G Superalloy

研究了不同浇注温度下的K417G合金试样。结果表明,1 450℃浇注,合金中碳化物以块状为主,γ′相边缘钝化,γ′尺寸为1μm左右;1 500℃浇注,合金中碳化物以长条形为主,γ′相边缘清晰,立方度较好,γ′尺寸为0.8μm左右。1 450℃浇注的合金屈服强度及断裂强度均高于1 500℃浇注的合金。合金拉伸裂纹主要产生于碳化物处,1 450℃浇注的合金,碳化物尺寸较小,产生裂纹需要的应力较大;1 500℃浇注的合金,碳化物细长,碳化物断裂所需应力较小。在760℃/645 MPa条件下,1 450℃浇注的合金,平均持久寿命可达到219 h,而1 500℃浇注的合金,平均持久寿命仅为25 h。前者的断裂方式为穿晶断裂,后者为沿枝晶断裂,断口上存在有部分疏松组织。

The K417G alloy samples at various pouring temperature were studied.The results show that the morphologies of phase were different at pouring temperature 1 450 ℃ and 1 500 ℃ in K417G alloy.The block carbide was observed in alloy pouring at 1 450 ℃,the edge of γ＇phase has been blunted,the length of the γ＇phase is 1 μm.And long strip carbide was shown in alloy poured at 1 500 ℃,γ＇phase＇s edge was clear,cubic better,the length of the γ＇phase is 0.8 μm.The yield strength and ultimate tensile strength of alloy poured at 1 450 ℃ are higher than the alloy poured at 1 500 ℃.The tensile cracks are generated in carbides,for the length of carbide shorter in alloy poured at 1 450 ℃,and carbides slender in alloy poured at 1 500 ℃,the fracture of carbides required bigger stress in alloy poured at 1 450 ℃ than alloy poured at 1 500 ℃.The average stress rupture life was 219 h ofalloypoured at 1 450 ℃ at the condition of 760 ℃/645 MPa.But at the same conditions,the average stress rupture life was 25 h only ofalloypoured at 1500 ℃.The fracture of alloy poured at 1450 ℃ is transgranular fracture,but fracture ofalloypoured at 1 500 ℃ is along the dendrite and found some microporosities on fracture surface.