| TC18 titanium alloy is an important material for the main load-bearing components of the aviation structure,serving in the extreme environment of marine salt spray and hygrothermal for a long term.Its performance of the corrosion resistance and wear resistance is insufficient,which greatly hinders its application and development.Therefore,it is significant to design and develop high-quality coatings with anticorrosion and wear-resistant for TC18 titanium alloy.HVOF thermal spraying is widely used in the aerospace,defense-military industry,petrochemical industry and other fields with its high efficiency and quality.The technology of HVOF spraying WC powder is currently proven to be one of the most effective alternatives to the surface chromium plating as an effective means of surface strengthening.Reasonable spraying parameters can make most particles present the best deposition state.Quantitatively evaluate the effect of the spraying process parameters on the coating quality is the key to preparing high-quality coatings.The dynamic deformation behavior of particles cannot be captured in real time by experimental methods,more effective methods are urgently needed to study the sputtering behavior of multi particle deposition.The numerical simulation becomes the key method.In this study,based on the JP5000 system,the fullcycle numerical simulation of the spray deposition process was carried out.The effects of different parameters on the particle flight behavior,flame flow dynamic characteristic,particle impacting mechanism and coating growth process were investigated.The reliability analysis of the coating process parameters was performed by combining the response surface methodology to determine the optimal parameters,which was used to perform the coatings.Microscopic characterization experiments were conducted on the coatings to verify the validity of the results obtained from the numerical calculation,which provides a theoretical basis for the production and preparation of high-quality coatings.The main research contents are as follows:(1)A three-dimensional HVOF spraying model in flow field was established,and the changes of gas phase velocity,temperature and pressure during the spraying process were investigated according to the computational fluid dynamics(CFD)method.The content of each component in the combustion process was traced.By varying the spraying distance,O/F and particle diameter,the evolution of particle flight behavior during the spraying process was analyzed.(2)Based on the Euler-Lagrange(CEL)method,a three-dimensional random multi-particle deposition sputtering model was established.Combining the particle deposition flatness and spreading bonding,the evolution of the temperature,stress and strain fields on the coating and substrate during the deposition process was revealed.(3)Based on the reliability principle,the BBD method was applied to evaluate and verify the spraying parameters in the flow field calculation model and particle deposition model.By establishing response surface equations,the effects of spraying distance,particle size,O/F,and substrate temperature on the coating quality were calculated.The sensitivity of the parameters was calculated combing the Monte-Carlo method to obtain the optimal spraying process parameters.(4)Based on the calculated optimal process parameters for coatings,a threedimensional WC-12 Co coating growth model was established based on the Python scripts.It realized multilayer uniform coating growth by the birth-death cell method,and the transient evolution of the temperature,stress and strain fields during the coating growth process was revealed.(5)WC-12 Co coating was prepared according to the optimal process parameters.The WC-12 Co coating and TC18 substrate were tested and compared according to the experiment of mechanical properties and the material microscopic characterization.Under the seawater and salt spray corrosion environment,the corrosion resistance of the coating was tested and evaluated to verify the validity of the numerical simulation results. |
