Surface Modification Of NiCrAlY Coating Irradiation By High Current Pulsed Electron Beam

Thermal barrier coatings (TBCs) are employed as a layer that protects turbine components against high temperature. NiCrAlY coating is the key factor to affect the oxidation resistance of the TBC. A new electron beam treatment method was applied to the surface of LPPS-MCrAlY coatings to improve the oxide scale behavior.This paper of the experimental research includes two parts, In the first part:the sample has been sprayed on the directionally solidified Ni-based superalloy DZ4by the low pressure plasma spary (LPPS)with an NiCrAlY bond coat, followed by the irradiation of high current pulsed electron beam(HCPEB) with the pulse duration50/200μs and electron energy density of12-20J/cm2, the second part of this article:the sample has been deposited6%-8%Y2O3partially stabilized ZrO2(YSZ) ceramic top coating by electron beam physical vapor deposition(EB-PVD) after sprayed NiCrAlY coating by LPPS. After that, the sample is irradiation by the HCPEB with the pulse duration200/3μs and electron energy of10J/cm2. oxidation was performed isothermally in a furnace at samples at900℃in air for times up to100/200h.Oxidation of coated sample was conducted in a furnace ant a constant temperature of900℃in air.Samples of electron beam treated and original samples were analyzed after100,200h heat treatment. The samples were examined using transmission electron microscope (TEM), electron probe micro analyzer (EPMA), energy dispersive spectrometer (EDS), scanning electron microscopy (SEM) of the surfaces as well as the cross-sections accompanied by X-ray diffractometry for phase determination of the oxides.1. The experimental results of part one showed:The NiCrAlY coating is characterized by the β and γ/γ’ phase, the part of β phase translate to γ/γ’ phase after the irradiation. The high roughness of the coating surface is reduced by HCPEB, the HEPEB treatment leads to a smooth NiCrAlY coating surface, and the surface was remelted up to a depth for approximately several micrometers, but produces micro-cracks and round at the surface. And the treated samples appeared to have a strongly enhanced oxidation resistance with a small amount of spinel NiCr2O4and NiO formation in the α-Al2O3oxide scale, according to the investigations of the coating, the optimum irradiation parameters of HCPEB have been found, as shown below:energy density of HCEPB is in range of12-20J/cm2, pulse duration is200μs. 2. The experimental results of part two showed:The electron beam treatment with the pulse duration3μs provides much better conditions for formation fusion of NiCrAlY and YSZ. At900℃on the treated samples, an α-Al2O3oxide scale grows. The optimum irradiation parameters of HCPEB have been found, as shown below:pulse duration is3μs.