EFFECT OF THE TEMPERATURE-DEPENDENT RESIDUAL STRESSES OF DIAMOND COATED TOOLS WITH DIFFERENT ADHESION QUALITIES ON THEIR INTERFACIAL FATIGUE STRENGTH

摘要

The below investigations aim at quantifying the effect of the residual stresses, developed in the Nano-Crystalline Diamond (NCD) coating structure on the fatigue strength of NCD coating-substrate inter-phase boundary layer (IB layer) at operational temperatures up to 400 degrees C. A dynamic 3D-FEM thermo-mechanical model simulating the inclined impact test is employed in order to achieve this target. This FEM model takes into consideration the temperature-dependent residual stresses in the NCD coating. By means of this 3D-FEM model, the fatigue strength of the coating-substrate IB layer is quantified in terms of a shear failure stress (SFLS) for IB layer damage after 106 impacts. This metric also depends on the treatments conducted prior to the deposition of the NCD coating for enhancing the adhesion of the coating to its cemented carbide substrate. The results of the inclined impact test using NCD coated cemented carbide inserts with improved or insufficient adhesion, were employed as input data to these FEM calculations. The effectiveness of the conducted pre-treatments prior to NCD coating deposition can be assessed and quantified by decoupling the effect of residual stress in the NCD film structure on the interfacial fatigue strength.