METHOD OF DEPOSITING A THERMALLY SPRAYED COATING THAT IS GRADED BETWEEN BEING MACHINABLE AND BEING WEAR RESISTANT

摘要

A method of thermally spraying a coating onto the interior of a cylindrical surface which coating is graded between enhanced optimal machinability and enhanced wear resistance. The method comprises the steps of; (a) preparing a cylindrical bore surface of a light metal substrate cleansed of grease and oils and modified to alter any oxide film present thereon; (b) thermally spraying a deposit of metallic droplets or particles onto the prepared bore surface using metal wire or powder feedstocks (low carbon steel or stainless steel) and a primary atomizing gas that projects the droplets or particles as a spray, the droplets or particles having a chemistry capable of metallurgically bonding with the metal of the substrate, the spray being positioned to lay down a generally uniform coating of such droplets or particles; and (c) varying the chemical content of the atomizing gas in two or more stages to proceed from essentially a metal droplet oxide-forming gas (air or oxygen) to essentially an inert or non-oxidizing gas (nitrogen or argon) relative to the droplets or particles.