Reduction of operating clearance between the HP turbine and the shroud in the new generation of gas turbines is one way often used by engine manufacturers to improve efficiency. This implies developing a blade tip coating/shroud coating system to minimize the degradation (particularly blades wear) during eventual rubbing. In this study, the chosen systems are: - VPS NiCoCrAIYTa as HP blade tip coating, - Plasma-sprayed MCrAIY coatings deposited under various atmosphere as abradable coatings. In order to understand the wear mechanisms of these systems tribological tests (block on ring and fretting) were performed to study the influence of the coating microstructure on the wear mechanisms. The results were compared and correlated to those of rub tests performed with real engine components.