Determination of fracture toughness of a platinum-modified nickel aluminide coating by micromechanical testing

The fracture toughness of an industry benchmark platinum-modified nickel aluminide coating (RT22LT) is determined by microcantilever bending tests. Cantilevers are prepared in three microstructurally-different zones across the cross-section focused ion beam machining and then bent in-situ a nanoindenter scanning electron microscope. Elastic-plastic mechanics, combined with finite element analysis, implemented to compute toughness. It found that varies through its thickness: middle zone has highest (7.62 MPam), followed surface (6.59 interdiffusion lowest (4.89 MPam). main reason for such difference amount plastic deformation prior corresponding contribution energy release rate vary from zone. Observations show ?-phase matrix predominantly transgranular. However, morphology depends on precipitate content each higher gives rise more interfacial decohesion between ?-matrix precipitates. Analysis microstructural-compositional features their correlation component suggests plays major role variation zones. behaviours compared those reported literature rationalised Weibull analysis.