A method of forming an interstage seal including removing a diaphragm seal box (14) from a gas turbine compressor assembly (10) and removing a labyrinth sealing member (12) from the diaphragm seal box (14). An abradable material layer (34) may be deposited on the diaphragm seal box (14). A spray gun may be mounted in relation to an engine disk (16) of the gas turbine compressor assembly (10) for cold-spraying a quantity of particles toward the engine disk (16). The particles may be sprayed at a velocity sufficiently high to cause at least a portion of the quantity of particles to adhere to the engine disk (16). The spray gun may be controlled to deposit a quantity of particles on the compressor disk (16) to form a geometry (32) that will abrade the abradable material layer (34) during operation of the gas turbine compressor assembly (10). The geometry (32) abrading the abradable material layer (34) forms an interstage seal. Rotation of the engine disk (16) within the gas turbine compressor assembly (10) may be controlled during the step of controlling the spray gun. The diaphragm seal box (14) may be reinstalled within the gas turbine compressor assembly (10) so that the geometry (32) aligns with the abradable material layer (34).