Bill BeckmanDecember 9th, 2013

Wear of a Gas Turbine Friction Damper

MANE-6960Friction, Wear, and Lubrication of Materials

Overview Wear of a dry friction damper in turbine section of

engine investigated Blade excitation is one of many failure concerns due to

risk of cyclic crack propagation from dynamic loading coupled with high thermal and static loading

Turbine blade vibration amplitude mitigated by use of under platform “cottage-roof” damper to dissipate kinetic energy by means of frictional contact and heat generation

Theory and Methodology Archard’s law for adhesive wear: Relative tangential slip movement between damper

wearing surface and blade counter surface on the order of 25 micrometers

Damper wear due to adhesion and fretting cannot be avoided, but mitigated with appropriate materials

Low change in damper volume is essential in retaining vibrational damping capability over the lifetime of the component

Results Various hardness values of high temperature alloys

have an effect on damper wear rates Nickel and Cobalt-Chromium alloy hardness can range

from 165 BHN to 515 BHN in a high temperature environment

Surface modification by means of carburization can be an effective low cost solution over high bulk material hardness alloys

Conclusion Adhesive wear due to plastic deformation of asperity

and bulk material cannot be avoided over high cyclic loading

Increasing material hardness retains damping capability of the part over lifetime of engine operation

Gas carburizing further improves part capability Softer and lighter Ni alloy can behaves as high hardness Co-Cr

alloy for most of part lifetimeDamper volume

lost over lifetime

165 BHN

235 BHN

305 BHN

375 BHN

445 BHN

515 BHN

Carburized

19.8% 14.5% 11.5% 9.6% 8.2% 7.2% 9.8%