APPLICATION OF ANALYSIS METHODS TO OPTICAL IMAGES OF FRICTION SURFACE OF TI-AL-N BASED COATINGS TO CHARACTERIZE DAMAGE ACCUMULATION AND TO DIAGNOSE FAILURE UNDER TRIBOLOGICAL TESTS
Processes of damage accumulation and failure of thin ceramic coatings based on Ti-Al-N system deposited on ductile steel and brittle glass-ceramic substrates were investigated during tribological tests on conditions of dry friction. Fractal analysis as well as Fourier- and wavelet analyses of optical mages of coating friction surfaces were performed to characterize numerically their damage. The methods of spectral analysis (Fourier- and wavelet analyses) revealed well-defined correlation between the obtained numerical parameters and wear rate of the coatings at the steady-state wear stage. At the same time, the fractal dimension provided only estimation of dynamics of damage accumulation at the running-in stage but did not demonstrate such correlation at the steady-state wear stage.