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This study deals with thermal and mechanical modelling of plasma sprayed zirconia coatings on stainless steel substrates, with a NiCrAlY bond coat. Applications concern thermal barrier coatings (TBC). Typically a coating of some hundreds micrometers induces a decrease of some hundreds degrees on the substrate temperature following the thermal flux. NiCrAlY permits to regularise the gap of the dilatation coefficients between the substrate and the ceramic. The NiCrAlY improves the adhesion of the coatings by providing a transition between the level of residual stresses in the three layers. A numerical model is developed and integrated to the industrial code ABAQUS based on finite elements approximation to simulates these behaviours under a parametric study. [ABSTRACT FROM AUTHOR]

The applied thermo-mechanical loading during cutting process leads to an important tool failure especially when machining is effected on refractory super-alloys such as titanium and/or nickel based-alloys. Heat removal generated by tool/workpiece friction plays an important role in preserving the structural integrity of the cutting tool. Efficient heat removal in machining depends solely on the thermal properties of the tool and on their evolution with temperature and mechanical parameters (strain, strain rate, etc.). In the present work, the effect of these thermal properties on the produced wear during the machining of refractory alloys is particularly investigated. Finite-Element Analysis (FEA) and SEM-imagery were used to map the thermal conductivity within the affected tool zone. The results indicate that depending on the temperature rise, the tool-tip might undergo a severe drop in thermal conduction. This drop may locally restrict the ability of the tool material to dissipate the applied thermal load. This may nucleate thermally congested clusters within the tool-tip where the material completely loses the ability to transport heat. Thermal congestion renders an energetically active zone where the thermal energy available may be used to activate wear through different mechanisms. It is also found that the immediate layer under the surface of the tool tip is important to enhance the ability of the tool material to dissipate the thermal loads. The results also highlight the importance of matching the temperature dependant properties of the different coating layers in order to enhance delamination resistance. [ABSTRACT FROM AUTHOR]