Synchrotron nano-diffraction for advanced CVD coatings

Research Project, 2020 – 2021

Purpose and goal: CVD (Chemical Vapour Deposition) is a very important technique for Sandvik Coromant, which is used to coat cutting tools. The stresses in the coatings have a great impact on performance in cutting operations, especially for crack resistance. The project aimed to use nano-diffraction on MAX IV for to demonstrate how the technology can be used to measure stress profiles in thin (<10 micrometer) CVD layers by AlTiN, which in turn provides the opportunity to tailor stress profiles for optimised performance and service life. Expected results and effects: AlxTi1-xN grown by CVD is a new coating system within the metal cutting industry and at present only a few companies offer CVD AlxTi1-xN coated products.The development is still at an early stage and the connection between material properties and performance is not yet fully understood. Residual stresses is a key parameter for performance, but traditional techniques often have large uncertainties and cannot resolve the stress gradients. Combining synchrotron nanodiffraction and performance tests will facilitate development and manufacturing of high-performance cutting tools. Approach and implementation: Coatings deposited with different process parameters will be investigated using nanodiffraction at MAX IV. The samples will be prepared using advanced techniques (focused ion beam) and by determining the strains inside the material from the measured lattice parameters, residual stresses can be calculated. As the beam is much smaller than the coating thickness, changes in the stress through the coating thickness can be measured. The measured residual stress states as a function of process parameters will be correlated with cutting tests from Sandvik to explain cutting performance.