Turbine abradable layer with progressive wear zone having a frangible or pixelated nib surface

A method for reducing turbine engine blade tip wear, comprising:

• providing a turbine having a turbine housing, a rotor having blades rotatively mounted in the turbine housing, distal tips of which forming a blade tip circumferential swept path in the blade rotation direction and axially with respect to the turbine housing;
• inserting a generally arcuate shaped abradable component in the housing in opposed, spaced relationship with the blade tips, defining a blade gap there between, and the abradable component having:
• a support surface for coupling to the turbine casing;
• a thermally sprayed ceramic/metallic abradable substrate coupled to the support surface, having a substrate surface adapted for orientation proximal a rotating turbine blade tip circumferential swept path;
• an elongated first ridge projecting from the substrate surface across a majority of the circumferential swept path, having a pair of first opposed lateral walls terminating in a continuous surface plateau having a plateau height relative to the abradable substrate surface, the plateau defining a planform cross sectional width and length;
• and
• a plurality of second ridges projecting from the plateau, having spacing, planform cross sections height and groove dimensions selected so that the second ridges have less shear resistance than the first ridge;
• and
• operating the turbine engine, so that any contact between the blade tips and the abradable surface shears off at least one second ridge tip, so that remaining first ridge thereunder inhibits turbine gas flow between the blade tips and substrate surface.

A turbine engine, comprising:

• a turbine housing;
• a rotor having blades rotatively mounted in the turbine housing, distal tips of which forming a blade tip circumferential swept path in the blade rotation direction and axially with respect to the turbine housing;
• wherein the engine is capable of starting in both standard mode, less than 40-50 Mw/minute power output ramp up rate, and fast mode, equal to or greater than 40-50 Mw/minute power output ramp up rate, without modifying turbine blade tip gap;
• and
• a thermally sprayed ceramic/metallic abradable component having:
• a support surface for coupling to a turbine casing;
• an abradable substrate coupled to the support surface, having a substrate surface adapted for orientation proximal a rotating turbine blade tip circumferential swept path;
• an elongated first ridge projecting from the substrate surface across a majority of the circumferential swept path, having a pair of first opposed lateral walls terminating in a continuous surface plateau having a plateau height relative to the abradable substrate surface, the plateau defining a planform cross sectional width and length;
• a plurality of second ridges projecting from the plateau, each second ridge having respective planform cross sections smaller than the plateau planform cross section and second ridge heights smaller than the first ridge height, the second ridges separated by respective grooves.