Hi Wasif
to the Surface Engineering Forum.
From
https://www.gordonengland.co.uk/abradable.htm
Quote:The main application of thermal spray abradable coatings is for gas path clearance control in gas turbine engines. In an ideal situation, gas turbine engines would be manufactured with minimal clearance in the gas seal locations, but in the real world these clearances are very much larger to permit operation without catastrophic interaction between rotor and the casing. The clearance at the gas seal locations has a significant effect on the gas turbine engine efficiency which directly translates to fuel consumption. Thermal spray abradable coatings successfully reduce these clearances to a minimum, without the risk of catastrophic failure.
In an ideal world I would say 0%. The more material that is abraded, the larger the clearance becomes. So to a large extent it will depend on the design and construction of the engine.