Research On Microstructure And Performance And Finite Element Analysis Of Gradient Coatings

Domestic tuyeres are made of pure copper which is an important part of the blast furnace. The working conditions of tuyere is often so bad, such as abrasion form coal dust with high rate and erosion from burner gas with high temperature. At the present,in china the lives of tuyeres are about only two months. If tuyeres are changed frequently, the stability of the blast will cut down; the production of the blast will be reduced; the working strength of workers will be increased. Studying the means of improving the service life of tuyere is actual significance.In this paper, base on the application of tuyere, the gradient coating were designed, and the gradient coating were prepared by atmospheric plasma spraying (APS);the micro-morphology of the prepared coating was observed; the tensile test, thermal shock test, calculation of temperature field and thermal stress simulation of the prepared coating were carried out.The results showed that: A mount of the micro-cracks and pores exist in ceramic coating ,the pore of coatings are nearly spherical and rectangular. The NiCrAlY coating has the layer structure, and exist a mount of pore. When the temperature field reaches steady state, the maximum temperature and the lowest temperature of pure copper tuyere are 337℃and 38℃; the maximum temperature and the lowest temperature of gradient layered coating tuyere are 364℃and 38℃. The front of tuyere always receive the high temperature, the high temperature of pure copper tuyere directly effect on the pure copper, while the gradient layered coating tuyere is inside the coatings, effectively reduce the copper substrate temperature. Both the double-layer coatings and the gradient coatings have large residual stress in the fringe of coatings interface. Compared to double-layer coatings, the utility of transition layer recessive relaxed the stress mutation. Mechanical is the main combination ways of coating, the gradient coatings have higher bonding strength. Working within the gradient coatings is in most of the weak throughout the coating-substrate system. The thermal shock performance of (ZrO2-NiCrAlY) gradient coating is better than the thermal shock performance of (ZrO2/-NiCrAlY) double coating. After the 600℃heat treatment, the diffusion layer was appeared between the coating and substrate.