Open AccessMechanical properties of aluminized CoCrAlY coatings in advanced gas turbine blades
Author(s) -
J Kameda,
T. E. Bloomer,
Y Sugita,
A Ito,
Shigeo Sakurai
Publication year - 1997
Language(s) - English
Resource type - Reports
DOI - 10.2172/505288
Subject(s) - materials science , microstructure , ductility (earth science) , brittleness , coating , microprobe , indentation hardness , composite material , metallurgy , mineralogy , creep , chemistry
The microstructure/composition and mechanical properties (22-950 C) in aluminized CoCrAlY coatings of advanced gas turbine blades have been examined using scanning Auger microprobe and a small punch (SP) testing method. Aluminized coatings were made of layered structure divided into four regimes: (1) Al enriched and Cr depleted region, (2) Al and Cr graded region, (3) fine grained microstructure with a mixture of Al and Cr enriched phases and (4) Ni/Co interdiffusion zone adjacent to the interface SP tests demonstrated strong dependence of the deformation and fracture behavior on the various coatings regimes. Coatings 1 and 2 showed higher microhardness and easier formation of brittle cracks in a wide temperature range, compared to coatings 3 and 4. The coating 3 had lower room temperature ductility and conversely higher elevated temperature ductility than the coating 4 due to a precipitous ductility increase above 730 C. The integrity of aluminized coatings while in-service is discussed in light of the variation in the low cycle fatigue life as well as the ductility in the layered structure