A numerical study was realized in order to simulate the plasma spraying of a Mo/NiCrBSi powder mixture under atmospheric conditions. The influence of the spray parameters on particles' in-flight characteristics was investigated numerically. The PHOENICS CFD code was used for the computation of the plasma jets and an in-house code was developed for the modeling of plasma/particles interactions. In view of the high melting temperature of Molybdenum and the presence of a self fluxing alloy like NiCrBSi, the state of the Mo particles prior to their impact on the substrate (velocity, temperature) was regarded as one of the major element influencing the quality of the produced coatings. Different spray parameters were considered: the plasma gas was an argon/hydrogen mixture with two different total flow rates and three different hydrogen fractions. Corresponding experiments are presented and appear to be consistent with numerical results.

A mathematical model of the impingement of a plasma jet on a flat structure is proposed. This model can be used to predict temperature and velocity fields in the jet and in the near substrate region, but also to estimate thermal exchanges at the surface of this substrate. Different options were tested concerning the modeling of the near wall region and results indicate that a boundary layer calculation is necessary to predict the energy flux transferred to the substrate with a good accuracy. Nevertheless, the influence of the presence of the substrate on temperature and velocity fields was found to be important only in the near substrate region, indicating that the flow fields calculated from free jet modeling are accurate over the major part of the domain.

The mechanical properties (i.e., tensile and shear properties) of vacuum plasma spray copper deposits presenting different porosity levels were determined. The tensile properties of the copper plasma spray deposit appeared to strongly depend on the porosity level, but whatever was the porosity level of the sample, the fracture always exhibited a ductile character, with the failure cups expanding preferentially on the pores and secondarily on the grain boundaries of the annealed microstructures. The tests clearly shown that the material presented an isotropic ductile-plastic hardening behavior typical of copper based materials, but this behavior being significantly influenced by the porosity level of the deposit.