Adam Gilewicz

Surface Microstructure of Mo(C)N Coatings Investigated by AFM

MoCN coatings have been formed by cathodic arc evaporation using the mixture of acetylene and nitrogen and pure molybdenum target. The surface structure, in conjunction with x-ray data, was analyzed by atomic force microscopy (AFM). The AFM results show differently shaped grain forms on the surface of coatings investigated. The increase in carbon in chemical coatings composition results in the reduction in surface grain size and the increase in roughness of the coatings.

Application of dilatometry with modulated temperature for thermomechanical analysis of anti-wear coating/substrate systems

Abstract Modern vacuum-plasma surface modification technologies of tools for metal and wood machining are based inter alia on the deposition of thin gradient and multilayer protection coatings with a thickness of several micrometers. Exploitation of tools are frequently carried out in complex tribological nodes, where next to mechanical loads, there are significant changes in temperature at the interface of the tool/workpiece material; hence, the knowledge of the thermomechanical stability of the coatings operating under these conditions is an important criterion used in the processes of designing of wear-resistant coating technology. In this paper, the objects of research were three types of gradient PVD coating/molybdenum substrate systems, for which time courses of amplitudes of elongation and equivalent thermal expansion coefficients of the systems were measured. Experimental measurements were made using a temperature-modulated dilatometry using concepts of dynamic load thermomechanical analysis. It was demonstrated that the developed method allows a quantitative determination of the influence of the gradient layer type on the total elongation of the substrate of the system. It was also shown that the changes of thermomechanical properties of the systems during annealing process are correlated with the time evolution of the equivalent thermal expansion coefficient. In addition, using the concepts of transition function describing the continuous change of physical and chemical parameters as a function of the spatial variables and finite element method for each of the systems, the distributions of internal thermal stresses were determined.

Temperature modulation in dilatometric investigation of PVD substrate-coating systems

Temperature modulation technique and phase sensitive analysis is applied for investigation the thermal stresses induced at higher temperature in the space between coating and substrate. The method applying only phase shift parameter eliminates influence of the intensity variation of measured signal. Comparison with conventional application of temperature modulation is presented. Method gives comprehensive information about the state of coating which is usually immersed using amplitude analysis.

Investigations on the Thermo-Mechanical Properties of CrN/CrCN Gradient Coatings Using a Thermo-Dilatometric Method

The paper describes issues related to the use of dilatometric methods for the study of thermo-mechanical properties of PVD gradient coatings. Tests were conducted on three types of CrCN / CrN coatings, which differed in the nature of the change of physico-chemical parameters in the gradient transition layer, deposited on a molybdenum substrate with the use of the cathodic arc evaporation method. The scope of the experimental studies included an analysis of the changes of the thermal “extortion” of the substrate – PVD coating system during annealing processes. In parallel, for comparison purposes, a mathematical description was proposed of gradient coatings containing the transition functions of material parameters. These functions describe the changes of such parameters as the Youngs modulus, the Poissons ratio, the thermal expansion coefficient, and the density as a function of spatial variables. Using the mathematical description proposed, numerical calculations of the state of thermal stress and strain for coatings are represented, respectively, by the transition function forms (a stepped, square, and square root) were carried via FEM. Based on the experimental and computational results obtained, the comparison between the elongation of the tested samples, and the state of thermal stress and strain in the substrate-gradient coating systems analysed were all specified.

Wear and Corrosion Behavior of CrCN/CrN Coatings Deposited by Cathodic arc Evaporation on Nitrided 42CrMo4 Steel Substrates

In the paper, the results of wear and corrosion tests of the CrCN/CrN multilayer coatings, formed by cathodic arc evaporation on 42CrMo4 (AISI 4140) steel substrates are presented. The substrates were subjected to thermo-chemical treatment–nitriding with various nitriding potential. The results of nitriding were determined by XRD and the hardness profile in the samples cross-section. The morphology of thin coatings was examined with SEM. A Vickers FV-700 and Fisherscope HM2000 hardness testers enabled to investigate hardness of steel substrates and CrCN/CrN coatings respectively. A pin-on-disc wear tests were used to determine the hardness and tribological parameters of the coatings: the coefficient of the friction and wear rate. The scratch test and Rockwell test were applied to assess the adhesion of the coatings to the substrates. The corrosion properties of coating–steel substrate systems were investigated using potentiodynamic polarisation tests. Corrosion potential, corrosion current density and polarization resistance were determined. It was found that that the nitriding of steel substrates improves properties of the coating–substrate system. The nitriding 42CrMo4 steel substrate with low nitriding potential enable to obtain substrates without surface “white layer” what favours good adhesion of the coating to the substrate. The CrCN/CrN multilayer coating–steel substrate systems show good mechanical and tribological properties and corrosion resistance.