Friction and Wear of Sintered Fibermetal Abradable Seal Materials

Three abradable gas path seal material systems based on a sintered NiCrAlY fibermetal structure were evaluated under a range of wear conditions representative of those likely to be encountered in various knife-edge seal (labyrinth or shrouded turbine) applications. Conditions leading to undesirable wear of the rotating knife were identified and a model proposed based on thermal effects arising under different rub conditions. It was found, and predicted by the model, that low incursion (plunge) rates tended to promote smearing of the low density sintered material with consequent wear to the knife-edge. Trade-off benefits between baseline 19 percent dense material, a similar material of increased density, and a self-lubricating coating applied to the 19 percent dense material were identified based on relative rub tolerance and erosion resistance.