Thermal fatigue of functionally gradient coatings processed by plasma spray method

• Main Authors: Zhong-Ren Wu, 吳中仁
• Other Authors: Hsien-Kuang Liu
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/54387384140599193421

碩士 === 逢甲大學 === 材料與製造工程所 === 95 === As far as application of Atmosphere Plasma Spray (APS) method is concerned, insulation coating on the surface of components is widely used to enhance heat-resistance in high-temperature condition. Nevertheless, thermal fatigue failure often occurs when coating materials undergo a rapid change in temperature. In this proposed study an advanced APS is used to fabricate functionally gradient materials as thermal barrier coatings. Performance of conventional plasma-coating and functionally gradient coating fabricated by APS is compared. In conventional plasma coating, ZrO2/MgO is coated as thermal barrier coatings (TBCs) with MCrAlY (wherein M is Ni, Co or Fe or composite alloy of the three elements) as insertion between substrate and TBCs. Basically conventional coating method uses same materials with advanced but being developed in a different way, the former refers to a method of coating an insertion on a substrate then ceramics layer is coated on, while the latter is to graduated adjust/change the structure and components to produce a ceramics coating layer on insertion. After coating layer being produced, porosity, tensile strength and icro-hardness are measured, and thermal fatigue tests were conducted to compare performance of coatings formed by conventional plasma-coating method and the advanced functionally gradient materials (FGM) approach. The experimental results suggest that FGM better enhances thermal fatigue resistance by showing less cracks on specimens than that by conventional plasma coating. Moreover at 900oC in air, Ni–base functionally gradient thermal barrier coatings demonstrate better thermal fatigue performance than Co-base’s.