Piotr Myśliński

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.

Irreversing thermal expansivity of materials coated with adhesive thin films detected by modulated-temperature dilatometry and differential thermal analysis

Usability of simultaneous modulated-temperature dilatometry (MT DIL) and modulated-temperature differential thermal analysis (MT DTA) for the quantitative description of degradation kinetics of wear-resistant film adhesion to the substrate as a function of temperature are presented in this work. The reversing thermal expansion coefficient of materials as a parameter sensitive to the relaxation of mechanical thermal stresses in films tested was used for this purpose. Sample experimental results allowing the process of film degradation to be described as a function of increasing temperature are quoted. Usefulness of this method considering the films deposited at diversified process parameters is also substantiated.

Characterization of the ceramic coating of iron with TiN by temperature-modulated dilatometry

Arc-evaporated ceramic films such as TiN, TiCN, and TiAlN find application for enhancing wear-resistance of tools for metal cutting. The wear-resistance is influenced by adhesive forces between film and substrate, which may be degraded by residual and imposed stresses, leading to delamination and damage of coating. The aim of this work was to find a relationship between physical properties of the coated iron and thermally induced stresses detected by dilatometry. Samples of iron coated with layers of TiN were investigated. In order to obtain more details about the degradation process of adhesion, the dilatometric analysis was carried out simultaneously with differential temperature and magnetometric analysis. The significant increase in thermal response was achieved by applying temperature modulation, a novel method in this field.

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.

Changes of thermal, mechanical and magnetic properties of an amorphous Fe80Cr5B15 alloy during magnetic and structural phase transitions

Thermal, mechanical and thermomagnetic properties associated with the magnetic and structural transition of an amorphous Fe80Cr5B15 alloy are described. The investigation was carried out in a simultaneous dilatometric and thermomagnetic experiment. An anomaly of the thermal expansion coefficient at the Curie point and a change in mechanical properties just before the onset of crystallization are observed. The results are compared with the thermal behavior obtained by differential scanning calorimetry.