Defect accumulation in nanoporous wear-resistant coatings under collective recrystallization. Simulation by hybrid cellular automaton method

Abstract

A modification of a multiscale hybrid discrete-continual approach of excitable cellular automata is developed. The new version of the method is completed by taking into account porosity and nanocrystalline structure of a material and the algorithms of calculation of local force moments and angular velocities of microrotations. The excitable cellular automata method was used to carry out numerical experiment (NE) for heating of continuous and nanoporous specimens consisting of nanocrystalline TiAlC coatings. The numerical experiments have shown that nanoporosity allows to substantially reducing the rate of collective crystallization. Nanoporosity slowed down propagation of the heat front in specimens. This fact can play both positive and negative roles in deposition of coating and its further use. On the one hand, by slowing the heat front propagation one can significantly reduce the level of thermal stresses in deeper layers of the material. On the other hand, such deceleration in case of the high value of the coefficient of thermal expansion can give rise to the formation of large gradients of thermal stress, which initiate nucleation and rapid growth of the main crack.