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The effect of sintering and CMAS on the stability of plasma-sprayed zirconia thermal barrier coatings

机译：烧结和CMAS对等离子喷涂氧化锆热障涂层稳定性的影响

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摘要

State of the art thermal barrier coatings (TBCs) for gas turbine applications comprise (7 wt.%) yttria partially stabilized zirconia (7YSZ). 7YSZ offers a range of attractive functional properties – low thermal conductivity, high thermal expansion coefficient and high in-plane strain tolerance. However, as turbine entry temperatures are raised, the performance of 7YSZ coatings will be increasingly affected by sintering and environmental contamination, by calcia-magnesia-alumina-silica (CMAS) deposits.The effect of sintering-induced stiffening on the driving force for spallation of plasma-sprayed (PS) TBCs was investigated. Spallation lifetimes of TBC specimens sprayed onto alumina substrates were measured. A simple fracture mechanics approach was employed in order to deduce a value for the strain energy release rate. The critical strain energy release rate was found to be constant, and if this value had been known beforehand, then the rationale presented here could be used for prediction of coating lifetime.The effect of vermiculite (VM) and volcanic ash (VA) contamination on the sintering-induced spallation lifetime of PS TBCs was also investigated. The presence of both VM and VA was found to accelerate the rise in their Young’s modulus with sintering. Spallation results show that coating lifetime may be significantly reduced, even at relative low addition levels, due to the loss of strain tolerance caused by the penetration of glassy deposits. This result gives a clear insight into the role CMAS plays in destabilizing TBCs.Finally, the adhesion characteristics of ingested volcanic ash were studied using a small jet engine. The effects of engine speed and particle size were investigated. Deposition on turbine surfaces was assessed using a borescope. Deposition mainly occurred on the nozzle guide vane and blade platform. A numerical model was used to predict particle acceleration and heating in flight. It was observed that larger particles are more likely to adhere because they have greater inertia, and thus are more likely to impact surfaces. The temperature of the larger particles at the end of its flight was predicted to be below its softening point. However, since the component surface temperatures are expected to be hotter, adhesion of such particles is probable, by softening/melting straight after impact.
机译：用于燃气轮机应用的现有技术的隔热涂层（TBC）包括（7重量％）氧化钇部分稳定的氧化锆（7YSZ）。 7YSZ具有一系列引人入胜的功能特性-低导热率，高热膨胀系数和高面内应变容差。然而，随着涡轮机入口温度的升高，氧化钙镁铝氧化铝（CMAS）沉积物将对烧结和环境污染产生越来越多的7YSZ涂层性能影响。烧结引起的硬化对剥落驱动力的影响研究了等离子喷涂（PS）TBC的数量。测量了喷涂在氧化铝基材上的TBC标本的剥落寿命。为了推断应变能释放速率的值，采用了简单的断裂力学方法。发现临界应变能释放速率是恒定的，如果事先知道该值，则此处提出的原理可用于预测涂层寿命。.石（VM）和火山灰（VA）污染对还研究了烧结引起的PS TBC的剥落寿命。发现VM和VA的存在会加速烧结的杨氏模量。散裂结果表明，由于玻璃状沉积物的渗透导致的应变耐受性下降，即使在相对较低的添加量下，涂层的使用寿命也可能会大大降低。该结果清楚地了解了CMAS在稳定TBC中的作用。最后，使用小型喷气发动机研究了摄入的火山灰的粘附特性。研究了发动机转速和颗粒尺寸的影响。使用管道镜评估涡轮机表面的沉积。沉积主要发生在喷嘴导流叶片和叶片平台上。使用数值模型预测飞行中的粒子加速和发热。观察到较大的颗粒更可能粘附，因为它们具有更大的惯性，因此更可能撞击表面。预计较大颗粒在其飞行结束时的温度将低于其软化点。但是，由于预计部件表面温度会更高，因此通过在冲击后直接软化/熔化，这些颗粒很可能会粘附。

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    Shinozaki Maya;

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  • 年度 2013
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