氯化物熔盐体系电沉积铱及其组织结构和抗高温氧化性能

Microstructure and high-temperature oxidation resistance of iridium coating electrodeposited from chloride-based molten salts

[目的]随着航空航天技术的迅猛发展,对飞行器热端部件的性能要求日益严苛。金属铱(Ir)因具有超高的熔点、优异的耐蚀性、高强度及稳定的物理化学性能,被认为是热端部件理想的防护层材料。[方法]采用NaCl-KCl-CsCl-IrCl_(3)氯化物熔盐体系在高纯铼片表面电沉积Ir。通过热重分析初步确定了电沉积的适宜温度范围,再通过扫描电镜(SEM)和能谱仪(EDS)研究了温度和阴极电流密度对Ir镀层表面形貌和元素组成的影响。采用X射线衍射仪(XRD)分析了较优条件下制备的Ir镀层的晶相结构,并通过高温烧蚀检测了其抗高温氧化性能。[结果]NaCl-KCl-CsCl-IrCl_(3)熔盐体系在490℃时开始熔解,596℃开始挥发,且挥发速率随着温度的升高而升高,650℃左右时挥发速率达到0.5%/min。该熔盐体系电沉积的适宜温度范围为550~650℃。当温度为600℃、阴极电流密度为0.2 A/cm^(2)时,所得Ir镀层连续致密、纯度高,呈(111)晶面择优取向的面心立方多晶结构,并且抗高温氧化性能良好。[结论]通过调控氯化物熔盐体系电沉积工艺参数能够制备连续致密的纯Ir镀层,并且其抗高温氧化性能有进一步提升的空间。

[Introduction]With the rapid advancement of aerospace technology,the performance requirements for the hot-end components of aircraft are becoming increasingly stringent.Iridium(Ir),known for its exceptional melting point,excellent corrosion resistance,and high strength,along with stable physicochemical properties,is considered as the ideal protective coating material for hot-end components.[Method]Iridium coating was prepared on high-purity rhenium substrate by electrodeposition in NaCl-KCl-CsCl-IrCl_(3)molten salts.The suitable temperature range for electroplating was firstly determined through thermogravimetric analysis.The effects of temperature and cathodic current density on the surface morphology and elemental composition of Ir coating were studied by scanning electron microscopy(SEM)and energy-dispersive spectroscopy(EDS).The phase structure of Ir coating obtained under the optimized conditions was analyzed by X-ray diffraction(XRD),and its resistance to high-temperature oxidation was tested by high-temperature ablation.[Result]The NaCl-KCl-CsCl-IrCl_(3)molten salts began to melt at 490℃and volatilize at 596℃.The volatilization rate of the molten salts was increased with the increasing of temperature,and up to 0.5%/min at a temperature of 650℃.The suitable electrodeposition temperature was from 550℃to 650℃.The Ir coating electrodeposited at temperature 600℃and cathodic current density 0.2 A/cm^(2) was continuous,compact,highly pure,and featured a face-centered cubic polycrystalline structure with preferred orientation of(111)and good resistance to high-temperature oxidation.[Conclusion]A continuous,compact,and pure Ir coating can be prepared by adjusting the electrodeposition parameters of chloride-based molten salts,and its resistance to high-temperature oxidation can be further improved.