摘要
对CMSX-4合金表面Pt改性铝化物(NiPtAl)高温涂层进行了短期高温氧化实验,研究了NiPtAl在1150℃形成表面氧化膜的微观结构。结果表明,氧化1h后形成的氧化膜包含亚稳态和稳态Al_2O_3区域,同时部分区域发生氧化膜脱落,并在氧化膜内部观察到空洞和Pt颗粒。分析表明,在涂层初期氧化过程中,NiPtAl涂层表面亚稳态q-Al_2O_3向稳态a-Al_2O_3转变,导致氧化膜中a-Al_2O_3与q-Al_2O_3呈区域层状分布,氧化1 h后Ni Pt Al涂层表面会形成约0.5 mm厚的q-Al_2O_3层。随着q-Al_2O_3的快速生长,NiPtAl中b-NiAl向g'-Ni_3Al转变,由于Pt在g'相比b相中溶解度小而发生偏析,从而导致在氧化膜a-Al_2O_3与q-Al_2O_3层界面处含有Pt颗粒。另外,初期Al_2O_3层的快速生长导致氧化膜内部形成空洞,氧化膜的生长和相变导致的内应力和内部空洞等缺陷降低了表面q-Al_2O_3层的黏结性能,最终导致氧化层脱落。
NiPtAI coatings are widely used as overlaying coatings besides bondcoats for thermal bar- rier coating (TBC) systems within high temperature environment. Oxidaiton behavior of NiPtAI coatings is mainly contribution for the failure of TBC systems or overlaying coatings. An initial oxide layer growth characteristics play a key role in extending lifetime of TBC system or overlaying coatings. In this work, the oxidation experiments of the Pt modified aluminide coating on CMSX-4 Ni-based alloy were carried out at 1150 ℃ for 1 h in 80%Ar+20%O2. The microstructures of oxide on the NiPtAI coatings are studied by OM, SEM, TEM and Raman spectroscopy. The results indicated that the oxide layer on the NiPtAI coatings included stable and met-stable AI203 after 1 h oxidation, and part of spalled oxide layer as well as pores within the oxide layer. The 0.5 μm thickness whisker-like 8-AI203 could form on NiPtAI coating during the initially oxidation stage. At the initial oxidation stage 8-AI203 fastly grew which resulted ,β-NiAI to γ'-Ni3Al,l transformation. The Pt particles formed on the inter-surface between a-AI203 and 8-AI203 layer due to a less Pt solid solubility in γ'-Ni3Al compared to/^-NiAI in the coating. Fast growth of initial AI203 could induce pores formation within the alumina layer. The pores and stress due to oxidation and phase transformation could decrease the alumina adherence, and at last result in the oxide spallation.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2017年第11期1504-1510,共7页
Acta Metallurgica Sinica
基金
国家自然科学基金项目No.51401097~~
关键词
NiPtAl
高温涂层
初期氧化
AL2O3
生长特征
NiPtAI, high temperature coating, initially oxidation, AI203, growth characteristics