脱氧对精密铸造K403镍基合金铸件的影响

通过在K403镍基高温合金真空熔炼过程中添加0.02%的Ca及0.002%的C并于1 650℃保温5min实现充分脱氧。发现未经过脱氧处理的铸件表面易出现裂纹而导致铸件报废。而经脱氧后成形的镍基高温合金精密铸件外部未观察到裂纹且内部夹杂物明显减少。通过扫描电镜及电子探针表征铸件的微观形貌,发现未经脱氧处理的铸件内部氧化物夹杂较多且易偏聚于裂纹周围,而经脱氧处理后的铸件内部夹杂物密度明显降低。

Influence of Deoxidization on Investment Casting Nickel-base Superalloy

Element Ca and C with a mass fraction of 0.02% and 0.002%,respectively,were added into K403 nickel-base superalloy during vacuum melting in order to deoxidize the alloy at 1 600℃ for 5 min before casting.The results reveal that a number of cracks can be observed on the casting surface without deoxidization treatment for the Ni based superalloy,which directly leaded to the scrapping of investment castings.It is found that the formation of cracks is suppressed efficiently after deoxidization and the number of impurities are obviously decreased.The microstructure of the castings with and without deoxidization treatment was observed through optical microscope and electronic probe.Vast oxide impurities were observed in the investment castings without deoxidization,of which the majority were distributed around the cracks.The impurities are decreased obviously in the investment castings with deoxidization,which may be the main factor for the suppression of cracks.