Thermal expansion of MCrAlY alloys

The thermal expansion behaviors of thirteen plasma-sprayed MCrAlY and related coatings, plus Tribomet TM-309 and its NiCo matrix were determined. Replicate runs to 1100 °C in argon for all coatings allowed the experimental variability and reliability of differences between coatings to be described. Wet chemical analysis of eight samples allowed multiple correlations between coating expansion and composition to be found. The model equations give calculated expansions at 525 and 825 °C within a few 0.1 mm/m of the original measurement for most coatings. The model and the original expansion data both show a NiCrAlY alloy, such as LN-33 has significantly lower expansion than current CoNiCrAlY coatings. Using low expansion NiCrAlY as a bondcoat is predicted to generate longer thermal cycle life of TBC coatings due to reduced expansion-induced interface stress with the YSZ ceramic.