Raman Spectroscopy Of Residual Stress Of Alumina Coating And Its Application

Alumina is widely used as coating material for high speed cutting tools because of its excellent performance.Due to the performance difference between the coating and the substrate material,especially the difference of thermal expansion coefficient,there are inevitably residual stresses in the coating that affect its service performance.Micro-raman spectroscopy is a potential method for residual stress measurement of coatings.However,there are still some fundamental problems to be solved when it is applied to residual stress measurement of alumina coatings.The Raman spectroscopy of residual stress of alumina coating and its application are studied in this paper.In this paper,in the absence of lattice dynamics equation of alumina material,the Raman frequency shift-stress component theoretical relation of arbitrary orientation alumina coating is derived based on piezoelectric spectral coefficient of the main crystal axis of single crystal alumina and euler rotation matrix.The visibility of Raman vibration modes with different polarization configurations was calculated by combining Raman tensor and polarization characteristics of alumina.The relationship between the polarization Raman intensity and the crystal euler Angle in different laser incident directions is derived.The method of determining the euler Angle of crystal according to miller exponent is given.Aiming at the oriented alumina coating material with specific texture,the quantitative relationship between Raman frequency shift-plane stress component measured on the surface and cross section of alumina coating is determined.Respectively according to the relationship of miller indices and crystal euler angles,under different incident direction of laser polarization Raman intensity and the relationship between euler Angle and the CAD geometry graphic method,calculating,measuring the sample surface and cross section of euler angles,combined with different crystallographic axis corresponding pressure spectrum coefficient,single crystal alumina is given?0 1-1 2?,?1 1-2 0?texture orientation alumina coating the surface of the samples and cross section of Raman frequency shift-quantitative relation between plane stress component.Based on the determined Raman frequency-stress component quantitative relationship between the surface and section of alumina coating,the residual stress distribution on the surface of alumina coating and the distribution of residual stress along the depth of the layer are further measured and analyzed in this paper.The residual stress distribution on the surface of alumina coating with different thickness and alumina coating with different sandblasting processes was measured.The results showed that the residual stress value of the thick coating sample was greater than that of the thin coating sample,The residual stress of ZrO₂ wet sand blasting process was more uniform than that of untreated samples,The residual stress level of the A1₂O₃ wet sandblasting process was lower than that of the untreated sample.By cross section Raman measurement,it is found that the residual stress of the coating from the surface of alumina coating gradually increases.Finally,the deviation range of stress results obtained by using the same Raman frequency shift-stress quantitative relation between surface and section is calculated and analyzed.