Large amount of dust can be ingested into the engines of aircraft and helicopters in sandy fields. Any ingested particles through the compressor impact the airfoil surface causing progressive erosion of the blades. To protect compressor components from erosion, thin films have been developed. Studies have shown that W base coatings produced by PVD deposition, can be a good solution to protect Ti-6Al-4V blades. We have simulated the impact of sand particles in order to optimize such coatings. Our first aim is to know whether the loading could be described by a quasistatic approach or needed a complete dynamic calculation. It is made for wide range of radii of particles supposed to be spheres and of impact velocities. To be representative of experimental conditions, the dynamic character cannot be ignored. Explicit finite element simulations give rise to the amplitude of the stresses inside all the components (particle, coating, substrate). During impact time, depending on the initial particles velocities, on the depths of the layer and on the sphere radii, the stresses inside the sphere can increase faster than in the layer and than in the substrate. They also reach locally the limit of rupture. So the particle might break before the stresses become critical in the other components. Our second aim is the improvement of the model by taking into account the initial compressive residual stress field in the coating.