Stress relaxation through thermal crack formation in CVD TiCN coatings grown on WC-Co with different Co contents

Rafael Panayiotis Stylianou, Dino Velic, Werner Daves, Werner Ecker, Andreas Stark, Norbert Schell, Michael Tkadletz, Nina Schalk, Christoph Czettl, Christian Mitterer

Publikation: Beitrag in FachzeitschriftArtikelForschungBegutachtung

9 Zitate (Scopus)

Abstract

TiCN coatings were grown by chemical vapor deposition (CVD) on WC-Co substrates with different Co contents, in order to control thermal stress. The driving force for the development of thermal stress is attributed to the difference between room and deposition temperature (ΔT ≈ −780 °C), and the mismatch of the coefficient of thermal expansion (CTE) between substrate and coating. Co contents of 6, 7.5, 10, 12.5, and 15 wt% were utilized to adjust the CTE of the substrate, and therefore tune the stress in TiCN coatings. Dilatometry of the substrates and high temperature X-ray diffraction of a powdered TiCN coating indicate a decreasing CTE-mismatch for increasing substrate Co contents. In consequence, residual stress in TiCN determined by X-ray diffraction increases up to 662 ± 8 MPa with decreasing Co contents down to 10 wt%. For Co contents below 10 wt%, the residual stress decreases. The formation of thermal crack networks in TiCN, analyzed by scanning electron microscopy, coincides with 10 wt% Co. Stress relaxation in TiCN coatings through the formation of thermal cracks becomes evident. A finite element simulation utilized for the calculation of residual stress distributions reveals shielding effects, which occur with the introduction of thermal cracks. Discrepancies between experimental and simulated thermo-elastic stresses imply the presence of secondary relaxation sources. High temperature residual stresses in TiCN, determined up to 1000 °C (i.e. above deposition temperature), suggest additional thermal crack formation for substrate Co contents of 6 wt%.

OriginalspracheEnglisch
Aufsatznummer105102
Seitenumfang9
FachzeitschriftInternational journal of refractory metals & hard materials
Jahrgang86.2020
AusgabenummerJanuary
Frühes Online-Datum16 Okt. 2019
DOIs
PublikationsstatusVeröffentlicht - Jan. 2020

Bibliographische Notiz

Funding Information:
The authors would like to thank Dr. Peter Schoderböck and Dr. Christian Saringer for the insightful discussions and generous support, in addition to Dipl.-Ing. Christoph Kickinger for high temperature X-ray diffraction measurements of the TiCN powder. The Austrian Federal Ministry for Digital and Economic Affairs and the National Foundation for Research, Technology and Development , in addition to the Austrian Research Promotion Agency (FFG) within the framework of the EOC 4 T project (grant number: 853857 ), is gratefully acknowledged for financially supporting this research. The authors also gratefully acknowledge the financial support, under the scope of the COMET program within the K2 Center “Integrated Computational Material, Process and Product Engineering (IC-MPPE)” (grant number: 859480 ). This program is supported by the Austrian Federal Ministries for Transport, Innovation and Technology (BMVIT) and for Digital and Economic Affairs (BMDW), represented by the Austrian Research Promotion Agency (FFG), and the federal states of Styria, Upper Austria and Tyrol.

Publisher Copyright:
© 2019 Elsevier Ltd

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