Research On High Temperature Properities Of YSZ/Al Composite Coatings On The Surface Of GH4169 Alloy

GH4169 superalloy is widely used in aerospace and has become the main material for manufacturing turbine disks and blades in aeroengines.Thermal barrier coatings play an important role in further improving the operating temperature of superalloys,prolonging service life and reducing fuel consumption.At present,plasma spraying technology is widely used to produce the thermal barrier coatings.However,there are many pores and cracks on the surface of the prepared thermal barrier coating.In order to solve these problems,the metal Al layer is prepared by radio frequency magnetron sputtering technology on the surface of the thermal barrier coating prepared by plasma spraying in this paper.The purpose of this method is to form a composite thermal barrier coating to further improve the oxidation and corrosion resistance of the thermal barrier coating.The surface and cross-section morphology,element distribution and phase composition of the two thermal barrier coatings prepared by the best process were analyzed by SEM,EDS and XRD.A series of mechanical properties of the coating were then measured.The high temperature oxidation behavior of plasma sprayed thermal barrier coating and YSZ/Al composite thermal barrier coating at different temperatures was compared and the oxidation mechanism of the two were analyzed.The corrosion behaviors of plasma sprayed thermal barrier coatings and YSZ/Al composite thermal barrier coatings in molten CMAS environment were compared and the corrosion mechanisms of the two were analyzed.The results show that:?1?The plasma sprayed thermal barrier coating prepared by the optimum process has a thickness of about 300?m,and the thickness of the YSZ/Al composite coating is about310?m.The coatings are well bonded and the elements chang uniform.Compared with the surface morphology of the plasma sprayed thermal barrier coating,the surface of the YSZ/Al composite thermal barrier coating has no undulations and no obvious holes and cracks.The surface of the plasma sprayed thermal barrier coating mainly exists c-ZrO₂ and t-ZrO₂ phases,while the surface of the YSZ/Al composite thermal barrier coating also has the presence of Al phase.?2?The surface of the YSZ/Al composite thermal barrier coating has a lower hardness and modulus of elasticity.At the same time,the roughness RMS value of the YSZ/Al composite thermal barrier coating is only 131.705,while the roughness RMS value of the plasma sprayed thermal barrier coating is 194.691.The surface of the YSZ/Al composite thermal barrier coating is significantly smoother.The bonding force between the metal layer and the ceramic layer in the YSZ/Al composite coating is about 74.6N.?3?The plasma sprayed thermal barrier coating performs well at 750°C and 850°C and has good oxidation resistance.However,after oxidizing at 950°C for 60 hours,the cracks and pores inside the coating rapidly expand and the coating peel off.The YSZ/Al composite coating maintains good oxidation resistance after oxidation for 100 hours at different temperatures,and there are no holes or cracks on the surface of the coating.?4?When the plasma sprayed thermal barrier coating is exposed to the molten CMAS corrosive environment,the volume expansion of the coating is caused by the phase transition of ZrO₂ due to corrosion.Plasma sprayed thermal barrier coatings begin to fail after 60 hours of CMAS corrosion.YSZ/Al composite thermal barrier coatings do not show obvious holes and cracks after 80 hours of corrosion in molten CMAS environment,and always maintain good corrosion resistance.