Study On Microstructure And Propreties Of Atmospheric Plasma-sprayed Nanostructured YSZ Coatings

In this paper,the bimodal micro structure YSZ coatings with different nanostructure contents were prepared successfully by atmospheric plasma spraying(APS)technology.During the process of coatings' preparation,the nano structured and agglomerated YSZ powders were employed and the molten decent of YSZ powders was controlled by changing the value of arc current with Ar-He-H2 as the working gas.In order to investigate the influence of the nanostructure content of YSZ coatings on the thermal cycle life,the thermal shock resistance of YSZ coatings were tested by water quenching method and compared with conventional YSZ coatings prepared under the same conditions.Finally,the nano structured coatings were heated at 1300? for 10 hours,and the thermal stability of the coatings was compared.The results show:(1)The nano structured YSZ coatings exhibit a bimodal microstructure consisting of partial melted area and full melted area.The nanostructure content of YSZ coatings prepared by Ar-He-H2 gas at 300A,400A and 500A was about 46.5%,40%and 31%,respectively.(2)The nano structured YSZ coatings and conventional YSZ coating were mainly composed of tetragonal(t)phase and non-equilibrium tetragonal(t).Nanostructured coatings exhibit a bimodal distribution of Vickers microhardness.The Weibull plots of the Vickers microhardness of the conventional coatings does not exhibit a bimodal distribution.Instead,single lines are noticed.(3)The thermal shock resistance test shows that the YSZ coating,whose nanostructure content is about 40%,has a better thermal shock resistance when compared with other nanostructure contents.When the nanostructure content is low(about 31%),the failure location mainly occurs between the ceramic coating and the adhesive layer.When the nanostructure content is high(about 46.5%),the failure location mainly occurs in the ceramic coating.The thermal shock resistance of nanostructured YSZ coatings are better than that of the conventional YSZ coatings.(4)After 1300? heat treatment for 10 hours,The thermal stability test shows that the nanostructured coatings still exhibit a bimodal micro structure.Meanwhile,the size of nanoparticles has had a certain degree of growth and hardness of all coatings were improved substantially.