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本文从中温断裂特征出发,论述了锆、铪、硼对铸造镍基高温合金中温性能的作用及枝晶间强化机理。认为在铸造镍基高温合金中,枝晶间是薄弱环节。提出了枝晶间强化与锆、鈶、硼之间的有机联系和共同特点:使共晶γ′增加,强化枝晶间;形成金属间化合物Ni_5Zr、Ni_5Hf和硼化物M_3B_2;加宽液相线-固相线距离。锆和鈶都改变MC碳化物的形态和成分,并攫取合金中的硫,形成稳定的高熔点的碳硫化物,争化枝晶间,提高枝晶间结合力。在研究合金化强化枝晶间薄弱环节的同时,还探讨了工艺参数的影响。认为工艺参数的变化,改变了合金的枝晶间状态。较快的凝固速度,细化枝晶,使共晶γ′量增加,减小共晶γ′和MC碳化物的尺寸,从而使合金得到强化。试验得出不同工艺的K5合金在760℃,66 kg/mm~2持久寿命与平均枝晶间距的关系。
In this paper, starting from the characteristics of medium temperature rupture, the effects of zirconium, hafnium and boron on the mid-temperature performance of cast Ni-base superalloys and the interdendritic strengthening mechanism were discussed. That in casting nickel-based superalloy, dendrite is the weakest link. The organic relations between dendrite strengthening and zirconium, gallium and boron are also discussed. The eutectic γ ’increases and dendrites strengthen, and intermetallic compounds Ni_5Zr, Ni_5Hf and boride M_3B_2 are formed. The widened liquidus - Solid line distance. Both zirconium and acenaphthene change the morphology and composition of MC carbides and grab the sulfur in the alloy to form a stable high-melting-point carbosulfide, thereby interlacing between dendrites and improving the interdendritic bonding force. In the study of alloying weakening the dendrite link at the same time, also discussed the impact of process parameters. It is considered that the change of process parameters changes the interdendritic state of the alloy. Faster solidification rate, refined dendrites, the eutectic γ ’amount increased, reducing eutectic γ’ and MC carbide size, so that the alloy is strengthened. The relationship between the average life span and average dendrite spacing of K5 alloy at 760 ℃ and 66 kg / mm ~ 2 was obtained.