Digital Repository, CONVEGNO IGF XXII ROMA 2013

Font Size: 
Microstructure and mechanical characterization of HVOF CoCrAlTa base coatings with different reinforcements
E. Cerri, P. Leo, G.P. Zanon

Last modified: 2013-06-27


High temperature oxidation causes degradation of materials in aircraft engines. Typical coatings like
MCrAlY (where M is Co, Ni or Fe) are used to prevent or retard oxidation. High Velocity Oxygen Fuel
(HVOF) is a thermal spray technique used in this field.
This work aims to characterize different reinforced CoCrTaAlY coatings that have been thermally sprayed on
CMSX-4 superalloy specimens by HVOF. The reinforcements were aluminum oxide, a mixture of Y, Zr and Aloxide
or TaC. The samples were exposed at 1100°C for long times (100-500 h) in air to develop oxidation.
Interdiffusion processes were activated at high temperatures and microhardness values decreased as a function
of time and distance from the surface. After 500h oxidation, hardness values in the coating surface were
comparable to that in the matrix, with a 25% reduction compared to the pre-oxidized condition. At the same
time, a strong aluminum oxide developed on the surface to protect the coating; the aluminum oxide was 5 μm
thick after 96 h and higher than 12 μm after 500h. Microstructure characterization was performed by light
microscopy and SEM.

Full Text: PDF