Thick Coatings and Surface Treated Materials
The high applied load (20 N) possible with the MicroTest loading head of the NanoTest, together with the range of techniques (depth-sensing microindentation, micro-scratch, micro-wear and micro-impact) make the system also ideally suited for testing and optimisation of the properties of coatings, either single layers or multilayers where the total thickness is greater than about 5μm.
Thermal spray coatings
Nanoindentation is a fast and convenient way to quantitatively characterize the complex microstructures of plasma sprayed coatings.
Research groups currently using the NanoTest to improve the quality of plasma sprayed and HVOF coatings include Prof. Subra Suresh's group at MIT, Prof. Sanjay Sampath's group at SUNY at Stonybrook, Prof. Bill Clyne's group at the University of Cambridge and VTT in Espoo, Finland. Research at SUNY and MIT in particular has shown the importance of modulus determination as an indicator of coating quality.
Multilayered CVD coatings
Optimisation of the performance of multilayered coatings is possible using a combination of micro-scratch, micro-wear and micro-impact testing to assess their micro-tribological behaviour and indentation to determine their mechanical properties. NanoTest users at CEROC/Safety centre near Tours, France, have tested coatings such as the tri-layer coating TiN-Al2O3-TiCN on WC-Co. In the example below, the improved scratch and wear performance of the multilayered coating is evident.
Micro-scratch tracks for (a) single layer (b) bilayer (c) trilayer coatings on WC-Co.
Variation in number of cycles to failure with applied load in the micro-wear test
Further reading
An investigation of the nanoindentation and nano/micro-tribological behaviour of monolayer, bilayer and trilayer coatings on cemented carbide BD Beake and N Ranganathan, Mater Sci Eng A 423 (2006) 46.
Improving thermal spray coating quality in the 21st century by nanomechanical property testing, Surface Engineering vol. 17 2001, 345.
