On the fracture behavior of Cr2AlC coatings. (August 2021)

• Record Type: Journal Article
• Authors: Völker, B.; Stelzer, B.; Mráz, S.; Rueß, H.; Sahu, R.; Kirchlechner, C.; Dehm, G.; Schneider, J.M.
• Is Part Of: Materials & design. Volume 206(2021)
• Publication Date: 2021-08
• Subjects: MAX-Phase -- Cr2AlC coatings -- Micro-cantilever -- In situ SEM testing -- Small scale fracture mechanics; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2021.109757
• Languages: English
• ISSNs: 0264-1275

Abstract

Graphical abstract: Highlights: The fracture toughness of the amorphous Cr2 AlC coating is significantly higher than for the crystalline Cr2 AlC coatings. The microstructure has a minor influence on the fracture toughness of crystalline Cr2AlC coatings. Crystalline Cr2 AlC shows brittle intercrystalline fracture. Abstract: Bulk MAX phase materials were investigated heavily in the last decades due to their advantageous combination of metallic and ceramic properties. In recent years, MAX phases also gained the interest of the protective coatings community. Cr2 AlC is a very promising material, since the crystalline MAX phase can be deposited at comparatively low (550 °C) substrate temperatures. Another advantage of the Cr2 AlC MAX phase is its self-healing ability. The goal of this investigation was to characterize the fracture toughness of Cr2 AlC protective coatings using in situ SEM micro-cantilever tests and to determine the influence of different microstructures on the fracture behavior. Surprisingly, the fracture toughness is only moderately affected by the microstructure of the crystalline samples investigated here, which reveal a fracture toughness ranging from 1.8 ± 0.1 MPam 1/2 to 2.4 ± 0.2 MPam 1/2 . In contrast to that, it could be shown that there is a significant increase in fracture toughness for the amorphous coating with identical chemical composition ( 4.1 ± 0.5 MPam 1/2 ) of almost twice the fracture toughness compared to the crystalline coatings. The detrimental influence of grain boundaries in the crystalline coating and the lack of grain boundaries in the amorphous sample might explain the formidable fracture toughness.