Effect of high temperature annealing on the properties of PtW thin film strain gauge on alloy substrate
In order to realize the health monitoring of the aero-engine hot components,a high temperature PtW thin film strain gauge was fabricated on GH4169 alloy substrate.The strain gauge consists of NiCrAlY transition layer,thermally grown oxide layer,YSZ/Al2O3 composite insulating layer and PtW sensitive layer.The microstructure of PtW films before and after annealing was investigated.After annealing,the grain size of PtW films increased,resulting in decreasing electrical resistivity.Meanwhile,the content of W decreased and the segregation of W at the grain boundary was observed.The strain-sensitive properties of PtW thin film strain gauge from room temperature to 600 ℃ were characterized with high temperature cantilever beam test.The results show that the gauge factor decreases with increasing temperature.Furthermore,the variation of the gauge factor becomes more severe after high temperature annealing.The upper limit of this PtW thin film strain gauge is as high as 1400με with good repeatability,which demonstrates great potential for surface strain measurement of hot components in aerospace field.
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