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熔模铸造K417G合金低压涡轮工作叶片通常需要进行表面细晶处理,在晶粒度检查过程中容易产生过腐蚀现象。通过试验考察了FeCl3腐蚀剂、CuSO_4腐蚀剂对K417G合金表面及性能的影响。结果发现,当采用CuSO_4腐蚀剂进行不同时间的腐蚀后,合金晶界处的碳化物会脱落而形成晶界损伤。合金在950℃、235 MPa条件下的持久寿命表明,当腐蚀5min时,对合金的持久性能不会产生太大的影响,但是当腐蚀时间延长至20min,合金的持久寿命会大幅度降低。当采用FeCl_3腐蚀剂进行不同时间的腐蚀后,合金晶界处的碳化物不会脱落。合金在950℃、235 MPa条件下的持久寿命表明,当腐蚀5min和20min时,合金的持久性能变化不大,但是当腐蚀时间延长至40min后,合金的持久寿命大幅度降低。这主要是FeCl3腐蚀剂对合金的晶界并没有产生损伤,但是随着腐蚀时间延长,合金枝晶间的疏松有扩大趋势,这导致了持久寿命的降低。因此,采用FeCl_3腐蚀剂用于叶片晶粒度检查较为适宜。
Investment casting K417G alloy low-pressure turbine blades usually need to fine-grained surface treatment, in the grain size check process is prone to over-corrosion phenomenon. The effects of FeCl3 etchant and CuSO_4 etchant on the surface and properties of K417G alloy were investigated. The results show that when the CuSO_4 etchant is used for corrosion at different times, the carbides at the grain boundaries of the alloy will fall off to form grain boundary damage. The long life of the alloy at 950 ℃ and 235 MPa shows that the long-term life expectancy of the alloy will not be greatly affected when the corrosion time is 5 minutes. However, when the corrosion time is extended to 20 minutes, the long life of the alloy will be greatly reduced. When the use of FeCl_3 etchant corrosion at different times, the carbide grain boundary alloy will not fall off. The long life of the alloy at 950 ℃ and 235 MPa shows that the lasting properties of the alloy have little change when the corrosion time is 5min and 20min, but the lasting life of the alloy is greatly reduced when the corrosion time is extended to 40min. The main reason is that the FeCl3 etchant does not damage the grain boundary of the alloy, but as the corrosion time prolongs, the looseness between the alloy dendrites tends to expand, which leads to the decrease of the durable life. Therefore, the use of FeCl_3 etchant for leaf grain size examination is more appropriate.