Abstract
A novel method is proposed for fracture toughness determination of graded microstructurally complex (Pt,Ni)Al bond coats using edge-notched doubly clamped beams subjected to bending. Micron-scale beams are machined using the focused ion beam and loaded in bending under a nanoindenter. Failure loads gathered from the pop-ins in the load–displacement curves combined with XFEM analysis are used to calculate K c at individual zones, free from substrate effects. The testing technique and sources of errors in measurement are described and possible micromechanisms of fracture in such heterogeneous coatings discussed.
Acknowledgements
We thank the Defense Research & Development Organization (DRDO), India, for funding this project. We also acknowledge Md. Zafir Alam, DMRL, Hyderabad for providing Pt-aluminide coatings for the tests and Dr A. Mahato (Mechanical Engineering, IISc) and T.S. Bhat (SUNY, Stonybrook, USA) for fruitful discussions on the FEM analysis.