Thermal Spraying for Offshore Wind Turbines – Keeping Corrosion and Friction at Bay

In general, offshore wind turbines (OWT) need different kind of protection depending of the regarded parts and functions. Thermally sprayed coatings represent a promising way to provide protection for complex geometries and large areas. Corrosion of the tower segments as well as slip in flange connections between foundation, transition piece, tower and nacelle constitute challenges solved by novel coating systems. Wire-arc sprayed ZnAl coatings with adapted phase composition promote the formation of favourable, stable and dense, corrosion products. For the flanges, Zn-based coatings with hard phases were designed to provide sufficient corrosion protection while increasing the friction coefficient and limiting creep. The main bearing of wind turbines represent another challenge. As a promising alternative, thermally sprayed coatings have been developed, allowing the first-time use of sliding bearings under such severe conditions instead. Therefore, Co-based coatings with hBN were developed, to reduce friction and wear under critical conditions, such as low relative velocities and high loads. These coatings are for instance validated in fields test near the coast of Helgoland in North Sea and demonstrator tests in a 1 MW main bearing test rig.