Failure Analysis of Ti6Al4V Gas Turbine Compressor Blades

A. Kermanpur, H. Sepehri Amin, S. Ziaei Rad, N. Nourbakshnia, M. Mosaddeghfar

Engineering Failure Analysis, Vol. 15, pp. 1052–1064, 2008

ABSTRACT

The failure mechanism of Ti6Al4V compressor blades of an industrial gas turbine was analysed by means of both experimental characterisations and numerical simulation techniques. Several premature failures were occurred in the high pressure section of the compressor due to the fracture of the blade roots. Metallurgical and mechanical properties of the blade alloy were evaluated. A 2D finite element model of the blade root was constructed and used to provide accurate estimates of stress field in the dovetail blade root and to determine the crack initiation in the dovetail.

The results showed no metallurgical and mechanical deviations for the blade materials from standards. SEM fractography showed different aspects of fretting fatigue including multiple crack initiation sites, fatigue beach marks, debris particles, and a high surface roughness in the edge of contact (EOC). The numerical model clearly showed the region of highest stress concentration at the front EOC of the blade root in the dovetail region, correlated closely with the experimentally characterised fatigue crack region. It was concluded that this failure has occurred due to the tight contact between the blade root and the disk in the dovetail region as well as low wear resistance of the blade root.

Keywords:

• Failure analysis; 
• Compressor blades; 
• Fretting; 
• Fractography; 
• Finite element analysis

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