Connect, no.128, January - February 2004, p.2

Nickel superalloy blades pass the test

Fig.1. L20A gas turbine and directionally-solidified high-pressure turbine blade Courtesy of Kawasaki Heavy Industries Ltd

Industrial Member company Kawasaki Heavy Industries Ltd (KHI) recently consulted TWI to assess the service life of newly developed turbine blades for the L20A gas turbine ( Fig. 1). This is a new 20 MW-Class gas turbine developed by KHI, for distributed generation, co-generation and combined cycle applications. Blades were made from directionally-solidified and polycrystalline Mar-M247 ^® and IN713C ^® alloys.

The development of advanced turbine blades has seen the introduction of a new range of directionally-solidified and single-crystal superalloys with compositions, microstructures and mechanical properties tailored to suit the demanding requirements of the high-pressure section. The project has provided considerable data on the long-term stability of the blade alloys and was able to demonstrate that the blades were fit for purpose.

Nickel superalloys are mainly strengthened by the precipitation of ' phase ( Fig.2), which forms coherently with the matrix. Detrimental microstructural changes may occur during high temperature service, degrading blade performance. Long-term stability is an important aspect of blade design and TWI were able to successfully demonstrate that the microstructure of the blades had not suffered any detrimental effects during service.

Fig.2. Scanning electron micrograph of the ' phase in a directionally-solidified blade Courtesy of Kawasaki Heavy Industries Ltd

For further details on how TWI can help you with regard to nickel superalloys, please contact Andrea Gregori. E-mail: andrea.gregori@twi.co.uk.

For general enquiries on gas turbines contact Chris Bagley. E-mail: chris.bagley@twi.co.uk

For information on KHI gas turbines contact Koji Take. E-mail: take_koji@khi.co.jp.