两种MCrAlY系复合涂层的制备和性能研究

IMR OpenIR

	两种MCrAlY系复合涂层的制备和性能研究
	马军
学位类型	博士
导师	孙超
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料加工工程
关键词	电弧离子镀电镀恒温氧化循环氧化热腐蚀 Arc Ion Plating Electroplating Isothermal Oxidation Cyclic Oxidation Hot Corrosion
摘要	"燃气轮机叶片用高温合金防护涂层通常需要兼顾两个方面的性能：一是须具有良好的抗高温氧化和热腐蚀性能，二是尽量避免涂层与基体的相互作用，如互扩散。通过改善上述两方面的性能，以提高涂层的长期使役寿命一直是研究者的重要目标。本论文工作采用电镀和电弧离子镀的联合工艺分别制备了普通MCrAlY涂层C1、具有多层结构的梯度复合涂层C2和原位生成Cr基扩散阻挡层体系C3。研究了涂层的沉积工艺和形成该多层结构的机制，并对各亚层的成分、结构进行了表征。分析表明，退火态的C2涂层具有双层结构：外部富Al（以β-NiAl相为主，并含有少量的Cr3Si或σ-NiCoCr相），内部富Cr（β-NiAl、γ′-Ni3Al和α-Cr等的混合相）。C3涂层则具有三层结构：外部以Al和Cr成分呈梯度分布构成梯度复合涂层（与C2类似）、涂层与基体界面处以α-Cr相为主形成扩散阻挡层。该Cr基扩散阻挡层是由沉积态的Ni-Re镀层在退火过程中原位转变而来，主要与外部的AlSiY层和MCrAlY层发生扩散型相变引起Cr、Co等原子内扩散有关。对比研究了C1涂层和梯度复合C2涂层在1150℃氧化后的氧化膜结构以及高温氧化性能（恒温和循环氧化）。结果显示，C1涂层表面在氧化初期形成了单一的α-Al2O3膜，但随着氧化时间的延长，表面氧化膜转变为非保护性的NiCr2O4尖晶石和α-(Al, Cr)2O3的混合物，氧化膜内部含有大量的孔洞，且氧化物有向内生长的趋势，导致涂层内部退化也非常严重，厚度大为减少，趋于失效。C2涂层的表面氧化膜结构在整个实验期间基本没有变化，氧化初期即形成双层结构：外部以粗大的NiAl2O4尖晶石和细小的α-Al2O3组成混合氧化层，内部是单一的α-Al2O3层。表面氧化膜的剥落区域很快会被新形成的α-Al2O3膜覆盖；涂层内部的退化以Al的损耗为主，氧化结束时仍含有约19 at.%的Al。研究了C2涂层在真空退火条件下涂层/基体互扩散对涂层退化的影响以及原位生成Cr基扩散阻挡层在长期氧化过程中对Al内扩散的抑制作用。同时，比较了C2和C3涂层在1000-1150℃范围的恒温和循环氧化性能差异。结果表明，在低氧压下表面氧化不占主导因素时，互扩散也会造成涂层的迅速退化；在涂层/基体界面处添加Cr基扩散阻挡层时，可以在较长时间内显著地抑制Al内扩散；由于C2和C3涂层对应的各亚层具有不同的成分（主要为有益微量元素含量），并且Cr基扩散阻挡层减缓了C3涂层的退化速度，因此，后者具有更为优异的长期氧化性能。研究了C1、C2和C3涂层在700和900℃下（Na2SO4+K2SO4）和（Na2SO4+NaCl）两种混合盐体系中的热腐蚀性能和腐蚀机制。腐蚀动力学曲线和结构分析表明，C3涂层的热腐蚀性能最好，C2涂层次之，C1涂层最差。"
其他摘要	"Usually, high temperature protective coatings need to give consideration two things: firstly, they must possess good anti-oxidation/corrosion properties; secondly, they need to avoid the interactions between coating and substrate, such as interdiffusion. It is always one of the most important objectives of researchers to enlong the lifetime of a coating via improving the abovementioned two properties. In this paper, a normal MCrAlY coating C1, a composite coating C2 with multilayer structure, as well as an in situ forming Cr-base diffusion barrier system C3 have been prepared by combining electroplating and arc ion plating method. The deposition processes, mechanism of forming these multilayer structures and detailed characterizations to the sublayer in the three coatings have also been performed. The results demonstrate that as-annealed C2 coating possesses double-layer structure: the outer layer is Al-rich with mainly β-NiAl plus some Cr3Si and/or σ-NiCoCr, the inner layer is Cr-rich composed of β-NiAl, γ′-Ni3Al and α-Cr. As-annealed C3 coating is trilaminar: gradient distribution of composition of Al and Cr in the outside (similar to C2 coating) and a diffusion barrier mainly consisting of α-Cr in the interface of coating/substrate. The Cr-base diffusion barrier is transformed by the original Ni-Re electroplated layer during annealing treatment, which is related to inward diffusion of Cr, Co, etc., resulted by the diffusion transformation between AlSiY layer and MCrAlY layer. The microstructure of oxide scale of C1 and C2 coating and the high temperature oxidation properties at 1150 °C have been comparatively investigated. The oxide scale on the surface of C1 coating is simplex α-Al2O3 at the initial stage, while prolonging the oxidation time it changes into less protective mixed structure composed of NiCr2O4 spinel and α-(Al, Cr)2O3 with massive holes and tends to grow into the inner coating, leading to greatly degradation and even failure of the coating. The oxide scale on C2 coating is nearly unchanged throughout the experiment. A duplex structure has been formed at the initial stage: the outer layer is composed of coarse NiAl2O4 spinel and fine α-Al2O3 particles; the inner layer is simplex α-Al2O3. The localized scaling zones produced during oxidation will be re-covered by newly formed α-Al2O3, which implies that C2 coating degenerates primarily by consuming Al-reservoirs despite 19 at.% Al have still been preserved. The effects of interdiffusion between C2 coating and substrate on coating degradation under the condition of vacuum annealing, as well as the inhibiting effect of in situ forming Cr-base diffusion barrier in C3 coating on inward diffusion of Al during long term oxidation have been investigated. Meanwhile, we have also compared the differences of C2 and C3 coating in the isothermal and cyclic oxidation properties at the range of 1000-1150 °C. The results show that interdiffusion can also degrade the C2 coating quickly even if surface oxidation does not occupy the dominant status; it can evidently retard inward diffusion of Al for a very long time when applying a Cr-base interlayer at the interface of C3 coating and substrate; since the corresponding sublayers in the C2 and C3 coating are various (mainly the compositions of beneficial elements), and the Cr-base interlayer slows down the degeneration of C3 coating, the latter possesses better long term oxidation properties. Hot corrosion properties and mechanisms of C1, C2 and C3 coatings at 700 and 900 °C have been studied using Na2SO4+K2SO4 and Na2SO4+NaCl mixed salts systems. Corrosion kinetics curves and microstructure analyses demonstrate that C3 coating exhibits the best hot corrosion properties, followed by C2 coating, and the worst C1 coating. "
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64504
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	马军. 两种MCrAlY系复合涂层的制备和性能研究[D]. 北京. 中国科学院金属研究所,2012.