Surface integrated thin film sensors for high precision measurement of temperature, wear, pressure and displacement in tribological contacts

This contribution deals with novel surface integrated thin film sensors which were developed for use at various mechanical components and tools. In general the sensors consist of hard coatings with optimized tribological properties well arranged to a wear resistant thin film system with inherent sensory properties. One class of sensors for measurement of temperature, force or pressure in mechanical contact zones is based on nano structured diamond-like-carbon films, which show an impressive piezoresistive effect (K > 100) besides excellent tribological properties. Because of the extreme hardness and high elasticity in the order of 15 - 30 GPa and 140 - 270 GPa, respectively, the coatings can be applied directly to mechanical parts. Examples of mechanical components with local sensors for measurement of load distributions, force detecting washers and ball bearings with micro load sensors in the race track of the balls are described. Another example for high precision measurement by use of surface integrated thin film sensors will deal with turning operations. To this the authors developed a wear resistant coating system for cutting tools based on hard Al2O3 films and an intermediate arranged thin film structure of hard TiN for measurement of surface temperature, wear, tool breakage and cutting edge geometry. Results on in-situ measurements at cutting of steel and aluminum will be discussed.