Key Issues And Applications Of Raman Spectroscopy In Measuring Residual Stressof Tool Coating

Understanding of the residual stres in the coating is essential for the design,manufacture,improving tool performance and extending tool life.Micro Raman spectroscopy technology has become an effective tool for non-destructive characterization of residual stress due to its unique advantages such as non-destructive,non-contact,and no special sample preparation,especially the small size of the light spot.Key issues and applications of Raman spectroscopy in measuring residual stressof tool coating are carried out,the scientific method for calibration of the zero-stress Raman frequency shift of the coating is explored,and the micro-area of the coating and the coating experience are carried out by using Raman spectroscopy.Measurement research on residual stress distribution after different degrees of wear.This article first studied the fitting of two complete and incomplete Raman bands and strong fluorescence Raman spectra of Ti Al N coating,and compared the repeatability of multi-peak fitting using Gauss and Lorentz peak profile functions respectively.And fitness,it is concluded that the notched Raman band should be fitted with Lorentz function,and the complete Raman band is more suitable for fitting with Gauss function.In this paper,the calibration method of the zero-stress Raman shift of the coating material is determined through comparative experiments.Two kinds of Ti Al N coating and Si substrate Cr₂O₃coating were used to carry out the Raman spectroscopy measurement experiment of scraping and heating to the preparation temperature,and the calibration method of the coating zero-stress Raman frequency shift was compared and determined.The experimental results show that the two methods of scraping powder and heating to the coating preparation temperature can be used to calibrate the zero-stress Raman frequency shift of the coating.In this paper,the residual stress changes of the coating samples in different temperature ranges are measured at the same time.The difference of the residual stress at different temperatures measured by the Raman experiment is consistent with the theoretical calculation results.In this paper,micro-Raman spectroscopy is used to study the local micro-area of chromium oxide coating on silicon substrate,including the deposition edge area where the electrode is placed,the crack micro-area and the residual stress of the large oxide particle micro-area.The thickness of the coating in the deposition edge area is determined by two methods:calculation using the color fringes observed in the deposition edge area and measurement with a step meter.Studies have shown that there is in-plane tensile residual stress in the chromium oxide coating.In the deposition edge zone,when the thickness of the coating is less than 0.8μm,the residual stress increases with the increase in thickness.When the thickness is greater than 0.8μm,the residual stress stabilizes between 0.55 and 0.75GPa.The stress is released at the microcracks,but the release is not complete;the large chromium oxide particles on the coating surface have almost negligible influence on the residual stress in the surrounding area.In this paper,Raman spectroscopy is used to study the residual stress evolution of Ti Al N coating on 304 stainless steel substrate after different degrees of friction and wear.Experimental results show that scratch wear will change the residual stress distribution of the coating,and even change the tensile and compressive properties of the residual stress,making the residual stress around the scratch change from compressive stress to tensile stress.The degree of wear is different,the influence range and size change of the residual stress are different,the deeper the scratch,the larger the influence range on the residual stress distribution,and the greater the influence on the residual stress value.