International audienceFive Al–Al2O3 coatings were deposited by gas dynamic cold spray, using feedstocks containing 0, 10, and 50 wt.% of Al2O3 particles admixed into commercially pure Al powders. Two feedstocks were made using Al2O3 powders with an angular, blocky Al2O3 morphology, two feedstocks used Al2O3 powders with a spherical morphology, and the fifth consisted of 100% Al. The influence of Al2O3 concentration and morphology in the feedstock powders on the cold spray coating formation was measured in terms of Al2O3 recovery in the coatings, deposition efficiency, and microstructural analysis. The Al–Al2O3 coatings were then subjected to dry sliding wear experiments from which the friction, wear, and microevolution of third body structures in the wear track and transfer film were observed. The spherical Al2O3 morphology was associated with improved tribological behavior compared to the angular morphology when comparing similar coating concentrations of Al2O3

The paper considers the behavior of third bodies in dry contacts. A description of the mechanism operating in contacts is given and the influence of external parameters outlined. Both physicochemical and mechanical conditions greatly influence third body behavior. Depending on third-body composition, the external influence can be more or less dramatic. Due to difficulties with experimentation, numerical modeling is suggested as a complementary tool. Two approaches for such modeling are described, the continuum and the discrete approach. At present these models are at an early development stage (two-dimensional simulations), and great efforts should be made for their further development. While an experimental apparatus can study phenomena at only one scale; namely the nanometer with AFM, or the micron to millimeter with fretting machines, modeling is able to range from the microscopic properties (particle interactions like coefficient of restitution) to the macroscopic properties by integration or averaging (load capacity, friction coefficient).