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In this study, we used the depth-sensing indentation technique to determine the cracking resistance of different PVD hard coatings deposited on tool steel substrates. By comparison, with the load–displacement curves, measured at the sites of carbide inclusion and a tempered martensite matrix in the D2 tool steel substrate surface, we observed different fracture mechanisms on TiAlN hard coating prepared by sputtering. Additional information about the deformation and fracture phenomena was obtained from the SEM images of FIB cross-sections of both types of indents. We found that the main deformation mechanism in the coating is the shear sliding along the columnar boundaries, which causes the formation of steps on the substrate surface under individual columns. Using nanoindentation test, we also analyzed the cracking resistance of a set of nl-(Cr,Al)N nanolayer coatings with different Cr/Al atomic ratios, which were sputter deposited in a single batch. From the indentation curves, we determined the loads (Fc) at which the first pop-in appears and compared them with the plasticity index H3/E2. A good correlation of both parameters was found. We also compared the indentation curves of the TiAlN coating, which were prepared by cathodic arc evaporation using 1-fold, 2-fold and 3-fold rotation of the substrates. Additionally, on the same set of samples, the fracture toughness measurements were performed by micro-cantilever deflection test. The impact of growth defects on the cracking resistance of the hard coatings was also confirmed. [ABSTRACT FROM AUTHOR]

In this study the use of AlTiN/aCN, TiAlN/TiN and three types of CrAlN/CrN coatings deposited on HSS steel was investigated. These protective coatings were prepared using PVD (physical vapor deposition) method. The objective of this study was to compare the microstructure, chemical composition and properties of Cr, Al or Ti based coatings deposited on a substrate made of high-speed steel HSS. The thicknesses of coatings based on titanium were approx. 4 µm, and those based on chromium were less than 1 µm. The morphology and chemical composition were studied using scanning electron microscopy (SEM) and X-ray dispersion spectroscopy (EDX). The X-ray photoelectron spectroscopy (XPS) method was applied. The adhesion was evaluated by scratch test. Nanohardness and durability tests of uncoated and coated knifes were performed. It was found that the knifes made of HSS covered with two-layer TiAlN/aCN coating exhibited the best durability characteristic. Coatings containing chromium were less durable due to their small thickness. The highest nanohardness was found in the AlTiN/TiN coating due to its multi-layer nature. The nanohardness of the other coatings is comparable but more than two times lower compared to the multilayer AlTiN/TiN nanocoating. [ABSTRACT FROM AUTHOR]

This paper details the analysis of the micro geometry in modified tools coated with the nano multi-layer TiN/AlTiN obtained by the PVD method. In standard replaceable cutting blades made of WC-Co before deposition, the radius of the blade rounding was increased from about 4 µm to about 13 µm using the drag finishing method with usage of OTEC company device. Next, the tools coated with the multilayer nano-coating TiN/AlTiN were subjected to blunting process. Mentioned above procedure was carried out on a standard 18 mm thick chipboard, assuming the blunting criterion (maximal tool wear on clearance face) Vbmax = 0.2 mm. In addition, previously blunted tools (modified and unmodified) were subjected to a detailed geometric analysis on a contact profilometer. Results show significant differences in the changes of various geometric parameters, in particular in the coefficients determining the asymmetry of the edge roundness denoted with letter K. Especially analysis of changes that concerns coefficient KR based on loss of cutting edge from rake face in comparison to clearance face suggests more intensive abrasive tool wear on rake face. Based on durability tests it can be supposed that changes in values of asymmetry coefficients in general described with letter K can decide about tool life. [ABSTRACT FROM AUTHOR]

In the present study, (Cr,Al)N nanolayer coatings with different Al/Cr atomic ratios were deposited by magnetron sputtering on different substrate materials (H11 and D2 tool steel, alumina). To prepare the (Cr,Al)N coatings with different Al/Cr atomic ratios in the same batch, we used two targets composed of two triangle-like segments together with two standard Al and Cr targets. This approach enabled us to study the evolution of structural and mechanical properties in dependence on composition. The elemental composition of the coatings was determined by energy-dispersive X-ray analysis (EDS). The phase composition of the (Cr,Al)N coatings was determined utilizing X-ray diffraction (XRD), while scanning electron microscopy (SEM) was employed to assess their morphology and microstructure. The coating surface topography was analyzed by atomic force microscopy (AFM). In order to evaluate the effect of the Al/Cr atomic ratio on the oxidation behavior, the (Cr,Al)N coatings were oxidized in ambient atmospheres at temperatures between 700 and 850 °C and subsequently analyzed by means of cross-sectional SEM and transmission electron microscopy (TEM). The oxidation rate, determined by weight gain over time, was utilized to quantify the oxidation process. The oxidation tests showed that the Al-rich (Cr,Al)N nanolayer coatings exhibit a considerably better oxidation resistance than the Cr-rich ones. We found that the oxide scale formed on the Al-rich coating is composed of double layers: a Cr-oxide top layer and an inner (Cr,Al) mixed oxide layer. In contrast, the oxide scale of the Cr-rich coating mainly consists of the Cr2O3 layer. In particular, we focused on the oxidation process occurring at the locations of growth defects. We noticed that the first oxidation products on the coated substrate occurred at a temperature that was much lower than the temperature for the (Cr,Al)N coating oxidation initiation. These products (iron oxides) formed only at the sites of those growth defects that extended through the entire coating thickness. [ABSTRACT FROM AUTHOR]