Challenges of Hardness Testing on Ceramic Materials

n industries, such as medical engineering, automotive or electrics, technical ceramics are used in a variety of products and also for coatings of components which have to be highly wear-resistant or temperature-resistant as well as non-conductive or non-corrosive. Beside characteristics like low density or limited thermal dilatation, ceramic materials also show high hardness but low fracture toughness and a high elastic modulus. Due to these mechanical qualities, ceramics are used, for example, in capacitors, isolators, cutting nozzles or blades, bearings, pumps or powder-coated metal surfaces. Hardness testing is particularly important to prove the mechanical strength of ceramic work pieces which are highly affected by wear; typical examples are friction bearings, brake disks or turbine blades. Probably the most common hardness testing method for ceramics is the Vickers procedure, usually with low-load test forces; but Knoop is also applicable for hardness tests on ceramiccoated layers due to its little indentation depth and minor crack formation