Method of depositing a thermally sprayed coating that is graded between being machinable and being wear resistant

A method of thermally spraying a coating onto an interior of a cylindrical surface, which coating is graded between machinability and wear resistance, comprising;

• (a) preparing a cylindrical bore surface of a metal substrate to be cleansed of grease and oils and modified to alter or remove any oxide present thereon;
• (b) thermally spraying a deposit of metallic droplets or particles onto said prepared bore surface using (i) metal wire or powder feedstocks, and (ii) an atomizing gas that projects the droplets or particles as a spray, said droplets or particles being capable of metallurgically bonding with said metal substrate, said spray being positioned, to lay down a generally uniform coating of such droplets of particles in initial and later stages, and (c) varying chemical content of said gas in two or more stages providing initially sprayed droplets or particles to have a higher hardness and wear resistance accompanied by decreased machinability when compared to the sprayed droplets or particles of the later stages, while the later stages of the sprayed droplets or particles have a decreased hardness accompanied by increased machinability when compared to the initially sprayed droplets or particles.