3D Assessment of Surface Integrity and Performance

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In many cases failure mechanisms initiate and propagate from the surface, including failure under corrosion, fatigue and wear. Critical to this is the surface finish (SF) and the surface integrity (SI). While surface finish has received much attention, surface integrity, a term used to describe the localised sub-surface region that differs from the bulk (residual stresses, plastic deformation, chemical changes, hardness, etc) has received much less attention. Traditionally people have used simple cross sections to examine the surface microstructure.In this project we will apply a suite of state-of-the-art methods to characterise as fully as possible the local microstructure in 3D across a range of scales. These include serial sectioning using a focused ion beam (FIB), mechanical sectioning and X-ray tomography. In the latter X-rays are used to obtain a 3D picture without mechanically sectioning the sample. Critical to the former methods are the means of removing material quickly and efficiently without introducing damage. Emerging methods to remove the damaged layer will be developed such that we can obtain EBSD, texture, chemical mapping, residual stress and insights into plastic deformation near-surface. This will lead to one of the best surface integrity assessment facilities in the world to support industry. In addition we will develop micromechanical methods to assess mechanical properties and corrosion and wear performance. In this way we will relate surface integrity to surface durability. This is critical if we are to predict and engineer surface performance. In addition to developing these metrology tools we will apply them to a set of industrial case studies including corrosion of stainless steel for the energy sector, the performance of thermal barrier coatings for the turbine engine sector, the wear performances of WC-Co coatings and nanostructured coatings. Further case studies will be identified by our industrial steering group.