The Effect of Surface Columnar Grains on Mechanical Properties in a Nickel-Based Gas Turbine Blade

M.R. Alizadeh¹ , M. Naseri² , A.M. Kolagar³

Section:Research Paper, Product Type: Journal-Paper
Vol.11 , Issue.4 , pp.20-24, Dec-2024

Online published on Dec 31, 2024

Copyright © M.R. Alizadeh, M. Naseri, A.M. Kolagar . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
 

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Abstract :
The morphology of surface grain of a gas turbine blade has always played a significant role on the mechanical and properties. In this pare, the effect of surface columnar grain on the mechanical properties has been studied on a Nickel-based gas turbine blade. For this purpose, two ceramic moulds were produced by coating ceramic layer. The moulds had different weights due to applying different number of ceramic layers on the moulds; one mould was heavier than the other. Then super alloy IN738LC was poured into the moulds and their surface grains was investigated. The results showed that there was some columnar grain in the blade which was in the heavier ceramic mould, while the other blade which was in the lighter mould, had no columnar grain size. Finally, three mechanical samples were prepared from each blade and their mechanical properties were compared. The test results showed that the mechanical properties of the blade with no-columnar grain were slightly higher than the other blade; in effect, the difference can be insignificant. In fact, the direction of the observed columnar grains was not exactly perpendicular to the airfoil to cause and propagate any cracks when stress is applying. In addition, the critical grains’ length was 80 mm that estimated the critical length of the grain which above that can be destructive and should be avoided.

Key-Words / Index Term :
Columnar grain, Mechanical properties, Ceramic mould, Investment casing, Nickel-Based super-alloy

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