| In this paper,the nanostructured zirconia thermal barrier coatings were prepared on GH3030 high temperature alloy surface by plasma spray.The nanostructured agglomerated ZrO2 feedstock was used as initial powders,and the NiCoCrAlY alloy as bond coating material..The relationship between bonding strength and spray current,secondary gas flow and spray distance were analyzed;The optimum parameters were acquired by orthogonal experimental design methods.The microstructures and phase structures of nanostructured zirconia thermal barrier coating were investigated thoroughly by SEM,FESEM,TEM and X-Ray.The coating forming process was simulated,also.The porosity,microhardness, bonding strength,thermal shocking resistance and high temperature oxidation resistance were test.The results showed that:the coating average crystal grain size were 44.7nm,which was larger than the nanostructured agglomerated ZrO2 feedstock.But it was nanostructured.The microstructure was composed of the melt zone and the partially-melt zone.The melt zone was consisted of columnar structure and equiaxed structure.The formation of columnar crystal was because the direction of grain growth was perpendicular to the substrate,while other directions were restrained.The formation of equiaxed crystal was because the molten particles was no time to grow up or grow slightly.There was no grain growth orientation and the growth rate was the same in all directions.The phase composition of the coating was the tetragonal(t-ZrO2) phase,and the monocline(m-ZrO2) phase was not discovered.Under this technological conditions,the average porosity was 10.61%;the average bonding strength was 45.63MPa,which was increased 23.4%by compared with conventional TBCs coating;the datas of microhardness were remarkably submitted to Weibull distribution; the thermal shock number of times was 55,45,40,respectively,at 1000℃,1050℃,1100℃; the coating oxidation kinetics curve approximatly matched parabola rule. |
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