Atmospheric Plasma Spray of a Zero Coefficient of Thermal Expansion Ceramic on Varying Metallic Substrates

Ceramic materials with zero coefficient of thermal expansion (CTE) can be used as coatings to alleviate thermal shock from high temperature applications such as fusion energy and high temperature reactor linings that can result in mechanical failure. However, CTE mismatch between the ceramic and the metallic substrates make deposition and adhesion of the coating challenging due to the thermal stresses induced during substrate cooling. This study uses atmospheric plasma spray (APS) to deposit a zero CTE polycrystalline ceramic, Al_0.5Sc_1.5W₃O₁₂, onto metallic substrates. Thermal stresses of the ceramic coatings were measured for a variety of metallic substrates with variable CTE’s. Temperature management and time off the substrates was used to mitigate thermal stress to the coatings while spraying. Tensile testing was performed to evaluate adhesion of the coatings once thermal stress in the coatings were allayed. This study demonstrates that zero CTE ceramics can be deposited onto a variety of substrates with no evidence of delamination once thermal stresses are reduced. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.