TY - THES

T1 - Arc evaporated CrTa(B)N hard coatings for cutting tools

AU - Gruber, Georg

N1 - embargoed until 25-02-2025

PY - 2020

Y1 - 2020

N2 - This thesis represents a step to illuminate the suitability of CrTaN and CrTaBN hard coatings for cutting applications. Only limited literature has been published on CrTaN coatings and, to the best of the author’s knowledge, no literature is available for CrTaBN coatings. For this study, five CrTaN and five CrTaBN coatings were deposited on cemented carbide substrates. The deposition parameters bias voltage, arc current and nitrogen pressure were varied for the different coatings. The influence of the deposition parameters on the chemical composition, microstructure, hardness and Young's modulus of the coatings was investigated by glow discharge optical emission spectroscopy, X-ray diffraction and nanoindentation, respectively. The coatings are mainly composed of a face centred cubic-Cr1-xTaxN solid solution. For the CrTaBN coatings a significantly higher hardness, compared to the CrTaN coatings, was observed. The hardness values of both investigated coating systems are higher than those of comparable CrN coatings. To investigate the influence of elevated temperatures on the microstructure, hardness and Young's modulus, three CrTaN coatings were annealed for two hours at 700, 800, 900 and 1000 °C. Up to an annealing temperature of 900 °C, mainly grain coarsening and recovery processes occur. After annealing at 1000 °C, decomposition of the Cr1-xTaxN solid solution under the release of N2 into hexagonal-Cr2N, hexagonal-Ta5N6 and (Ta0.8W0.2)C, which is formed at the interface between the coating and the substrate, was found. The degree of decomposition depends on the deposition parameters.

AB - This thesis represents a step to illuminate the suitability of CrTaN and CrTaBN hard coatings for cutting applications. Only limited literature has been published on CrTaN coatings and, to the best of the author’s knowledge, no literature is available for CrTaBN coatings. For this study, five CrTaN and five CrTaBN coatings were deposited on cemented carbide substrates. The deposition parameters bias voltage, arc current and nitrogen pressure were varied for the different coatings. The influence of the deposition parameters on the chemical composition, microstructure, hardness and Young's modulus of the coatings was investigated by glow discharge optical emission spectroscopy, X-ray diffraction and nanoindentation, respectively. The coatings are mainly composed of a face centred cubic-Cr1-xTaxN solid solution. For the CrTaBN coatings a significantly higher hardness, compared to the CrTaN coatings, was observed. The hardness values of both investigated coating systems are higher than those of comparable CrN coatings. To investigate the influence of elevated temperatures on the microstructure, hardness and Young's modulus, three CrTaN coatings were annealed for two hours at 700, 800, 900 and 1000 °C. Up to an annealing temperature of 900 °C, mainly grain coarsening and recovery processes occur. After annealing at 1000 °C, decomposition of the Cr1-xTaxN solid solution under the release of N2 into hexagonal-Cr2N, hexagonal-Ta5N6 and (Ta0.8W0.2)C, which is formed at the interface between the coating and the substrate, was found. The degree of decomposition depends on the deposition parameters.

KW - Arc evaporation

KW - CrTaN

KW - CrTaBN

KW - Mikrostructure

KW - X-ray diffraction

KW - Nanoindentation

KW - Thermal stability

KW - Lichtbogenverdampfen

KW - CrTaN

KW - CrTaBN

KW - Microstruktur

KW - Röntgendiffractometerie

KW - Nanoindentation

KW - thermische Stabilität

M3 - Master's Thesis

ER -