2.2. Morphology and microstructure observations

The microstructures of the coatings were evaluated by TEM and SEM cross-sectional imaging. AFM was used to observe the surface of the TiAlN, SiNx, TiAlN/SiNx, TiAlN+CNx, TiAlN/ CNx+TiAlN, and TiAlN/CNx+CNx coatings [4, 7]. The morphological characteristics of the coatings were measured with the use of AFM in dynamic friction mode (DFM) with a carbon nanotube tip having a radius of approximately 44 nm. The AFM system (Digital Instruments Nanoscope III, Hysitron Inc.) was used. Calculations were performed within the scanning probe image processor (SPIP) software, which is a standard program for processing AFM data at the nanoscale. The grain diameter and surface roughness of the coatings were determined by scanning an area 3 3 μm with the AFM. To investigate the effects of grain diameter on the surface morphology and the boundaries between the grains, simulations were performed to calculate the mean grain diameter and surface roughness of the scanning area. The coating surfaces were characterized with the use of the roughness analysis module; the values for surface roughness, average roughness (calculated by Sa: distance between peaks), and peakpeak roughness (calculated by Sy: height difference between the highest and lowest peaks in the image), were obtained by analyzing the images and cross-sectional profiles and measuring the mean grain diameter parameters.
