| 摘要 |
Thermally spraying a metallic coating onto light metal cylinder bore walls, where the walls carry a film of grease or oil resulting from machining operations, involves: (a) honing the walls; (b) (either concurrent with, or following, step (a)) washing the honed surface with a mildly alkaline solution which leaves an aluminate residue on the walls; (c) rinsing the surface to remove the solution but leave the residue; (d) thermally spraying the surface with a metallised bond; and (e) thermally spraying a top coat onto the bond coat, the top coat having increased wear resistance and lubricity. The honing is carried out to produce a net shape cylinder surface having spiral overlapping cross abrasions with some peaks and valleys folded over and moulded to create surface tears, folds or undercuts giving a hook and ladder effect. A machining coolant is used during honing to prevent burnishing of the walls. In step (b) the alkaline solution comprises an aluminate-forming agent and surfactants which provide for wetting of the walls even when steam is present in the solution. The spraying is done with such velocity, impact and heating such as to promote migration of the particles into the tears, folds and undercuts for mechanical interlocking with the honed surface as well as chemical interaction with the surface. |
