高温合金热障涂层材料系统的热机械疲劳行为

IMR OpenIR

	高温合金热障涂层材料系统的热机械疲劳行为
	陈竹兵
学位类型	博士
导师	朱世杰 ; 王中光
	2011
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	材料物理与化学
关键词	热障涂层热机械疲劳热喷涂 Thermal Barrier Coating Thermomechanical Fatigue Thermal Spraying
摘要	"热障涂层系统包括涂覆在金属基体表面的金属粘结层和陶瓷层，可有效地降低基体表面温度、提高器件的热效率、减少室温气体的排放，已广泛应用于涡轮发动机的高温部件。在服役条件下，高温部件如涡轮叶片不仅经历着热循环同时还遭受交变的机械载荷，即热机械疲劳载荷。因此，对热障涂层材料系统的热机械疲劳研究是非常重要的。本文分别利用大气等离子喷涂和超音速火焰喷涂在镍基铸造高温合金M963表面涂覆NiCrAlY金属涂层，然后对其进行了450-900 ℃高低两个应变幅下的同相位和反相位热机械疲劳试验。结果表明，两种体系试样在同相位相同应变幅下寿命基本相同；反相位下，高应变幅时等离子喷涂制备的涂层试样寿命较长，低应变幅时超音速火焰喷涂制备的涂层试样寿命长。通过断口和纵截面观察分析表明，同相位下，涂层中很少出现裂纹；反相位下，等离子喷涂的涂层体系中，裂纹一般从表面萌生，而超音速火焰喷涂的涂层体系，裂纹从表面或界面缺陷处萌生；同时发现等离子体系中基体裂纹密度比超音速火焰喷涂的高。研究了粘结层分别采用大气等离子和超音速火焰喷涂、陶瓷层采用大气等离子方式制备的两种热障涂层体系（A/A TBC和A/H TBC）在450-850 ℃ 下同相位和反相位热机械疲劳。结果表明，对于A/A TBC体系，相同应变幅下同相位的寿命较长；而A/H TBC体系，相同应变幅下反相位寿命较长。试样的失效方式随相位的变化而改变，同相位下两种体系试样失效方式相同都表现为正断，而反相位两种体系试样断裂时都伴随着表面涂层的开裂和剥落，但是两种体系开裂和剥落的界面不同。应用Suo-Hutchinson 模型得到界面断裂韧性，评价了粘结层的制备工艺对陶瓷层与粘结层界面结合强度的影响。通过计算试样在不同相位下的受力状态，分析了系统的寿命关系和涂层开裂行为。对两种热障涂层材料系统进行了1000 ℃下100 h 预氧化，发现仅在A/H TBC系统中陶瓷层与粘结层界面形成了连续的热生长氧化物层。然后对预氧化后热障涂层试样进行450-850 ℃ 下反相位热机械疲劳试验。结果表明，预氧化严重降低了试样的疲劳寿命。对失效后试样宏观观察分析得知，试样的失效方式随应变幅的变化而改变，在高应变幅下试样表现为正断；低应变幅下试样在断裂的同时伴随表面涂层的开裂和剥落。对试样纵截面观察表明，两种体系试样涂层剥离都位于陶瓷层内且靠近陶瓷层与粘结层的界面处。"
其他摘要	"Thermal barrier coating (TBC) system consists of a metallic bond coat deposited on the surface of the substrate and a top coat, which can efficiently reduce the temperature of the substrate, increase the power efficiency and decrease the greenhouse gas emission. It is widely used in the hot sections of gas turbine engines. In service, the hot sections such as turbine blades experience not only thermal cycling but also cyclic mechanical loading which is called thermomechanical fatigue (TMF). Therefore, it is important to investigate thermomechanical fatigue behaviors of thermal barrier coating systems. In this thesis, the nickel based superalloy M963 was coated with NiCrAlY metallic coating which was produced by air plasma spraying (APS) or high velocity oxygen fuel (HVOF). Then in-phase (IP) and out-of-phase (OP) TMF tests were performed on it in the temperature range of 450-900 ºC with two mechanical strains. Results revealed that the fatigue lifetime was similar to each other between the two systems under the same mechanical strain in the IP tests, while under the OP condition the lifetime of APS coated system was longer at high mechanical strain but at low mechanical strain the lifetime of HVOF coated system was longer. Observations of fracture surfaces and longitudinal sections showed that there was few crack in the coating under the IP condition, while under the OP condition cracks initiated at the surface of the coating in APS coated system but in HVOF coated system cracks developed either from the surface or from the interface between the coating and the substrate. The crack density for the substrate in APS coated system was higher than that in HVOF coated system. IP and OP TMF tests with the temperature range of 450-850 ºC were conducted on the two kinds of TBC system (A/A TBC and A/H TBC) with the bond coat fabricated by either APS or HVOF and the top coat deposited by APS. Results revealed that under the same mechanical strain the lifetime under the IP condition was longer for A/A TBC while for A/H TBC the lifetime was longer in the OP test. The failure behavior changed with the phase condition. In the IP and OP tests all the specimens failed in the gauge length while under the OP condition the specimen fractured with the cracking and spallation of the coating. But the interfaces of the cracking and spallation were different between the two TBC systems. The effect of the bond coat spraying techniques on the bonding strength between the top coat and the bond coat was evaluated by the interface fracture toughness through the Suo-Hutchinson model. The relationship of the lifetime between the IP and OP tests and the cracking behaviors of the coating for the two TBC systems was analyzed by the state of the stress. A continuous thermally grown oxide layer was formed between the top coat and the bond coat only for A/H TBC when the as-sprayed TBC system experienced isothermal oxidation at 1000 ºC for 100 hours. OP TMF tests were performed on the pre-oxidation TBC systems in the temperature range of 450-850 ºC. Results revealed that the fatigue lifetime of the pre-oxidation TBC systems was much shorter than that of as-sprayed TBC systems. Observations of failed specimens showed that the failure mode changed with the mechanical strain amplitude. All the specimens failed in the gauge length while at the lower mechanical strain amplitude the specimen fractured with the cracking and spallation of the coating. From the observation of longitudinal sections it was shown that the fracture of the coating was located within the top coat near the interface between the top coat and the bond coat for the two TBC systems"
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64278
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	陈竹兵. 高温合金热障涂层材料系统的热机械疲劳行为[D]. 北京. 中国科学院金属研究所,2011.