Fracture Toughness Measurement of Chromium Nitride Films on Brass
M Krishnamurthy, Ivar E. Reimanis, J Berger, Elizabeth S. Drexler
Two methods of measureing the fracture toughness of films are critically examined using well-characterized films of CrN and Cr2N approximately 6(mu)m in thickness bonded to brass. The first method invokes a model developed by Beuth and Klingbeil in which the film fracture stress is related to the fracture energy through an expression that accounts for work hardening of the substrate. The second method is to directly measure the displacement field around the crack tip using electron-beam moire, and subsequently to estimate the crack tip stress intensity factor using full field displacement equations. The films were prepared by magnetron sputtering on brass substrates heat treated at different temperatures, thereby altering the microstructure and hence the substrate yield stress. Unexpectedly, the same films deposited on different substrates lead to very different inplane compressive residual stresses. The effect on crack driving force is discussed and a comparison between these two methods is made. Both techniques agree resonably well, and reveal that CrN exhibits a higher toughness that Cr2N.
, Reimanis, I.
, Berger, J.
and Drexler, E.
Fracture Toughness Measurement of Chromium Nitride Films on Brass, Journal of the American Ceramic Society, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851332
(Accessed February 21, 2024)