Synthesis and Accelerated Testing of Oxynitride Films for High Temperature Applications

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NON-TECHNICAL DESCRIPTION:There is a critical need for new protective ceramic coatings that can operate in harsh environments with service temperatures in the 1000-1500oC range. These ceramic coatings must exhibit excellent heat resistance, chemical stability, fracture toughness and wear durability so they can be reliably be used in applications such high performance engines, shrouds, rotors, seals, slides, and bearings. A major problem is that conventional ceramic coatings crack and delaminate during thermal cycling in reactive gases at extreme temperatures. This project focuses on developing and testing Si-Al-O-N and Si-Zr-O-N thin film coatings and tailoring their properties to achieve high performance in terms of corrosion resistance, wear resistance, and fracture toughness. To efficiently test and evaluate the performance of the ceramic coatings in high temperature harsh environments, a microfabricated test platform is being developed, upon which the ceramic films are strategically deposited, to carry out accelerated testing under conditions that mimic those that are encountered during service. The project trains a graduate student and two undergraduate students in the areas of high temperature materials, thin film technology, and microfabrication, and K-12 students are being educated about high temperature materials science. Collaborations with industrial partners are being used to evaluate the effectiveness of the new coatings that are developed. TECHNICAL DETAILS:Ceramic thin film coatings that can withstand harsh environments with service temperatures of 1000-1500oC must exhibit excellent heat resistance, chemical stability, fracture toughness and wear durability. Conventional ceramic coatings crack and delaminate during service because of interdiffusion phenomena, chemical reactivity, and stress generation during thermal cycling in reactive gases at extreme temperatures. This project focuses on developing and testing SiAlON and SiZrON films that are precisely fabricated using magnetron sputtering and ECR-plasma-assisted e-beam evaporation. Nanoscale architectures are being investigated including gradient and multilayer compositions in order to achieve high performance in terms of corrosion resistance, wear resistance, and fracture toughness. To efficiently test and evaluate coating performance under thermal cycling conditions, a microfabricated MEMS test platform is being developed that consists of microheaters, temperature sensors, oxidation sensors, stress indicators, and microsliding fixtures. The project trains a graduate student and two undergraduate students in the areas of high temperature materials, thin film technology, and microfabrication, and K-12 students are being educated about high temperature materials science. Collaborations with industrial partners are being pursued to evaluate the effectiveness of the SiAlON and SiZrON coatings.