Microstructure uniformity detection of superalloy based on multi-channel ultrasound detection system for bars
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摘要: 高温合金锻件出现混晶或者组织不均匀现象时，材料的性能会下降，有效的超声无损检测方法可以对高温合金组织的均匀性进行评价。由于组织均匀性影响超声波信号在材料中的传播，故超声波在高温合金材料中的散射噪声分布，可以反映材料的组织差异。以某牌号高温合金锻造棒材作为试验对象，采用基于棒材的多通道超声自动检测系统进行超声波数据采集，在φ0.8 mm平底孔当量的灵敏度条件下对每个深度噪声信号进行分析。通过处理超声检测相应部位的显微组织数据，得到噪声信号的平均值与晶粒直径在99%置信区间显著正相关，噪声信号标准差与晶粒直径变异系数在95%置信区间显著正相关的结论。进一步结合聚类分析可以确定：当噪声平均值为1.6%~1.79%，噪声标准差为0.6~0.8时，材料为混晶组织；当噪声平均值为1.81%~2.6%，噪声标准差大于1时，材料含有树枝晶组织。Abstract: Mixed crystal or non-uniform structure of superalloy forgings will lead to the degradation of material properties. Effective ultrasonic nondestructive testing method can be used to evaluate the homogeneity of superalloy structure. Because the homogeneity of structure affects the propagation of ultrasonic signals in materials, the scattering noise distribution of ultrasonic waves in superalloy materials can reflect the structural differences of materials. Taking a certain grade of superalloy forged bar as research object, the ultrasonic data acquisition was carried out based on the multi-channel ultrasonic automatic detection system of bar, and the noise signal of each depth was analyzed under the sensitivity condition equivalent to φ0.8 mm flat bottom hole. According to the microstructural data of the corresponding positions by ultrasound detection, the average value of noise signal is positively correlated with the grain diameter in the 99% confidence interval, and the standard deviation of noise signal is positively correlated with the variation coefficient of grain diameter in the 95% confidence interval. Further cluster analysis can confirm that when the average noise is 1.6%-1.79% and the standard deviation of noise is 0.6-0.8, the material is mixed crystal structure. When the average noise value is 1.81%-2.6%and the standard deviation of noise is greater than 1, the material contains dendritic structure.
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Keywords:
- superalloy /
- microstructure uniformity /
- ultrasound /
- noise
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