Numerical Simulation Of PVD Processing And Spinodal Decomposition For TiAlN-based Coatings

TiAlN-based coatings are the most widely used hard coating materials for cutting tools due to its high hardness,good wear resistance and thermal stability.TiAlN-based coatings are generally prepared by physical vapor deposition(PVD)technology in the industry.The performance of TiAlN-based coatings largely depends on the microstructure formed during the PVD preparation process and the microstructure evolution during spinodal decomposition in service.The phase-field simulation is able to describe the microstructure evolution of TiAlN-based coatings during the preparation and service processing,providing theoretical guidance for the improvement of coating production and mechanical properties.TiAlN-based coatings are taken as the research objects in the present thesis,and the numerical simulation research for PVD coating preparation and spinodal decomposition process is conducted.Firstly,by combining high-throughput phase-field simulation and hierarchical multi-objective optimization strategy,the screening and design of TiN coating properties and processes are realized.Furthermore,the weak coupling strategy of PVD phase-field simulation and spinodal decomposition simulation of TiAlN coatings is developed to study the effect of PVD process stability on the coating service process.The major research achievements and innovations in the present thesis are described as follows.(1)Based on a large number of microstructure evolution simulation results of PVD coating deposition process,combined with experimental data such as average grain size,surface roughness,porosity and coating deposition rate,a quantitative relationship between process parameters,phase-field model parameters and coating characteristic properties was constructed.Then,by studying the Pareto front distribution law of coating properties under different process conditions,the mutual dominance relationship of different coating properties was analyzed.Ultimately,by using the hierarchical multi-objective optimization method,the model parameters and process parameters with the best performance of coatings were selected,and the process parameter design results consistent with the experimental design results were obtained.(2)Considering the influence of experimental noise in the PVD process,a weak coupling strategy of PVD coating phase-field simulation and spinodal decomposition simulation was proposed,and the numerical simulation of the microstructure evolution of TiAlN coatings in the spinodal decomposition process under different noise levels was successfully achieved.The results showed that the spinodal decomposition process of TiAlN coating at 1173 K has obvious stage characteristics,and there was a significant component separation phenomenon after aging/service.Comparing the effect of different noise levels on the simulation results of microstructure evolution,it can be found that the experimental noise generated by the preparation process has a remarkable impact on the component separation rate,average wavelength and energy evolution of the coatings.Based on the film growth phase-field model and the Cahn-Hilliard equation,the microstructure evolution simulation of the deposition process and service process of TiAlN-based coatings was implemented.The hierarchical multi-objective optimization strategy of coating performance screening and the weak coupling strategy of PVD coating phase-field simulation and spinodal decomposition simulation were developed,which can provide theoretical guidance for the PVD process design and performance optimization of TiAlN-based coatings.This thesis consists of 29 figures,3 tables,99 references.