Dynamic fracture of CrN coating by highly-resolved nano-impact

Nano-impact testing has provided localized high strain rate deformation information in either (i) repetitive impact for fatigue of brittle materials or (ii) high-resolution data acquisition of single impacts for energy dissipation and dynamic hardness in ductile materials. The current study focusses...

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Bibliographic Details
Published in:Surface & coatings technology 2020-02, Vol.383, p.125288, Article 125288
Main Authors: Shi, Xiangru, Li, Heng, Beake, Ben D., Bao, Mingdong, Liskiewicz, Tomasz W., Sun, Zhengming, Chen, Jian
Format: Article
Language:English
Subjects:
Acceleration
Brittle materials
Coating
CrN coating
Ductile fracture
Energy dissipation
Failure mechanism
Fracture toughness
High resolution
High speed tool steels
High strain rate
Impact analysis
Ion beams
Nano-impact
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Summary:Nano-impact testing has provided localized high strain rate deformation information in either (i) repetitive impact for fatigue of brittle materials or (ii) high-resolution data acquisition of single impacts for energy dissipation and dynamic hardness in ductile materials. The current study focusses on whether high-resolution data acquisition can be used to determine fracture occurring during a single impact event. A PVD CrN coating on 42CrMo4 high speed steel (HSS) was impacted with a cube corner indenter over a range of different acceleration forces. By analyzing the high precision depth-time curves during the first contact phase of the impact, an abrupt depth change was observed at and above 30 mN acceleration force. Focused ion beam technology confirmed through-thickness coating fracture without delamination on tests where the step was observed. The step was absent at lower force or on the more ductile HSS throughout the load range. The fracture dissipated energy and fracture toughness of the coating was estimated under 50 mN acceleration force based on the analysis of impact energy. The calculated dynamic fracture toughness of CrN coating is in the range of 2.75–7.74 MPa·m1/2, depended on the indenter geometry constant, which is comparable with the reported value of about 3.13 MPa·m1/2. •Highly-resolved nano-impact testing was used to evaluate the dynamic fracture of CrN.•The fracture of CrN can be indicated by the 1st contact cycle of impact curves.•The failure mechanism of CrN coating was investigated by FIB-SEM technology.•The dynamic fracture toughness was estimated based on the energy method.
ISSN:0257-8972
1879-3347
DOI:10.1016/j.surfcoat.2019.125288