摘要
MCr Al Y涂层在高温环境下可在涂层表面生成致密连续的氧化层,以阻止阳离子和氧离子的扩散,在保护镍基高温合金基体免受高温氧化和腐蚀方面发挥着重要作用。氧化层主要由α-Al2O3组成,其具有较高的热稳定性和化学稳定性,同时在其六方密堆积(HCP)结构中氧离子和金属离子具有较低的扩散系数。随着氧化铝层的生长,使得涂层/氧化层界面铝浓度降低,进一步抑制了连续的Al2O3层的生长,导致氧化层中形成混合氧化物和裂缝以及空隙。同时,伴随着界面扩散过程,使得氧化层的微观结构因化学成分的变化而转变,这将对涂层的抗氧化性能产生显著影响。在高温条件下,由于扩散的热活化特性及涂层与基体化学成分的差异,涂层/镍基合金基体界面扩散过程将对基体合金产生有害影响。此时,Al会从涂层内扩散至基体合金中,同时Ni会从基体合金扩散至涂层中,使得基体合金的微观结构发生相转变(γ-Ni相→γ’-Ni3Al相),形成互扩散区(IDZ)。镍基合金微观结构的相转变使得难熔元素析出,形成二次反应区(SRZ),其主要由富含难熔元素的拓扑密堆积(TCP)相组成,例如σ、μ和Laves相等,且具有枝状晶结构。因此,TCP相的析出将会对镍基合金的高温疲劳寿命产生严重影响。本文综述了MCr Al Y涂层界面扩散的详细过程,同时对界面扩散过程的影响进行了总结。这将有利于深入了解涂层在氧化过程中的组织结构变化和元素扩散行为,对提高涂层的高温抗氧化性能及研究涂层的失效机理具有借鉴意义。
MCrAlY coatings are playing an important role in protecting the Ni-based superalloy substrate from oxidation and corrosion at high temperature,which can form dense and continuous oxide scales on the surface to retard the diffusion of cations and oxygen.The oxide scale is mainly composed of byα-Al2O3 of high thermal and chemical stabilities as well as the low diffusivity of oxygen and metal ions in its hexagonal close-packed(HCP)structure.The concentration of aluminum in the coating near coating/oxide scales interface decreases with the depletion of Al for the growth of alumina layer,which further suppresses the consecutive Al2O3-scale growth,causing the formation of mixed oxide compounds and cracks as well as voids.Also,accompanied with the interface diffusion behavior,the microstructure of the oxide scales evolves due to the changes of the chemical composition,which makes a significant influence on the oxidation resistance property of the coating.At elevated temperature,the coating/Ni-based superalloy interface diffusion process will make deleterious effects because of its thermally activated nature and the difference in chemical composition.The inward diffusion of Al from the Al-rich coating and the outward diffusion of Ni from the Ni-rich superalloy,accompanied with the phase transformation fromγ-Ni phase toγ′-Ni3Al phase,will result in an interdiffusion zone(IDZ).Furthermore,the phase transformation will result in a secondary reaction zone(SRZ),which mainly consists of refractory element-rich topologically close-packed(TCP)phases,such asσ,μand Laves phases.These TCP phases with dendritic nature of solidification in the matrix may reduce the high-temperature fatigue life of the Ni-based superalloy.The interface diffusion process of MC AlY coatings is addressed in this paper,together with a summary of current understanding of the effects accompanied with the interface diffusion.This work can help to understand the microstructure change and element diffusion behavior of the MC AlY coatings in the oxidation process,which has guiding significance for improving the oxidation resistance and understanding the failure mechanism of the coatings.
作者
杨洪志
邹俭鹏
石倩
林松盛
代明江
王迪
Yang Hongzhi;Zou Jianpeng;Shi Qian;Lin Songsheng;Dai Mingjiang;Wang Di(State Key Laboratory of Powder Metallurgy,Central South University,Changsha 410083,China;Guangdong Institute of New Materials,National Engineering Laboratory for Modern Materials Surface Engineering Technology,Key Lab of Guangdong for Modern Surface Engineering Technology,Guangzhou 510651,China)
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2020年第7期2240-2249,共10页
Rare Metal Materials and Engineering
基金
Scientific Research Fund of Guangdong Province(2016A030312015)
GDAS’Special Project of Science and Technology Development(2017GDASCX-0202)
Natural Science Foundation of Hunan Province(2018JJ2524)
Guangdong Science and Technology Program(2017A070701027)
GDAS’Project of Science Technology Development(2017GDASCX-0111)
Guangdong Science and Technology Plan Project(2014B070705007)。
