采用不同重熔工艺制备K452合金试样,测试试样在900℃下的拉伸性能.结果表明:当浇注温度为1430℃时,试样的抗拉强度从410 MPa变化到510 MPa,延伸率从3.5％变化到22.0％,实验数据较分散;试样中O和N平均含量较高,尤其N含量达0.0028％之多;断口上存在大量疏松.当浇注温度提高到1500℃时,拉伸性能得到提高,试样中O和N的平均含量有所降低,断口上疏松减少.当合金经过1590℃保温5 min的高温净化处理,浇注温度仍为1500℃时,试样的拉伸性能大幅度提高,O和N的平均含量明显降低,断口上没有观察到疏松,实验数据具有较好的一致性.
K452 alloy is a nickel-based cast superalloy having the good tensile properties at high temperature and excellent corrosion resistance.It has been applied as a blade material of engines when environmental temperature is not above 950 ℃.It is found that the tensile properties of the alloy have become more scattered and unstable although its chemical compositions are not changed.Hence,the tensile properties of the alloy were studied in order to increase its stability at high temperature and improve its applied properties.Tensile specimens were prepared using the different re-melting processes.Tensile tests were done at 900 ℃.When the pouring temperature was 1430 ℃,tensile properties were not only lower than expected,but also had great degree of dispersion,ie.,the vales of ultimate strengths changed in the range of 410 MPa and 510 MPa,and the elongations changed in the range of 3.5％ and 22.0％,the average contents of O and N were the highest among three tested conditions.The highest N content was 0.0028％.And the shrinkage area was higher than those in other two re-melting processes.When the pouring temperature was 1500 ℃,the tensile properties were improved,and their changing scopes became small,the average contents of O and N decreased,the shrinkage area decreased.When the refining temperature was 1590 ℃ and the holding time was 5 min,both average contents of O and N were decreased greatly,the shrinkage was not seen in the fracture surfaces.And the tensile properties were improved.Furthermore,their changing scopes were very small.
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