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 accomplished by considering the porosity and nanocrystalline structure of a material and the algorithms of calculation of local force moments and angular velocities of microscale rotations. The excitable cellular automata method was used to carry out numerical experiment (NE) for heating of continuous and nanoporous specimens with nanocrystalline TiAlC coatings. The numerical experiments have shown that nanoporosity allows to substantially reduce the rate of collective crystallization. In so doing the nanoporosity slowed down propagation of the heat front in the specimens. This fact can play both positive and negative roles at deposition of the coatings and their 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 thermal expansion coefficient can give rise to the formation of large gradients of thermal stress, which initiate nucleation and rapid growth of a main crack.