Method and apparatus for application of thermal spray coatings to engine blocks

A method of applying a thermal spray metallic coating to cylinder wall portions of a cast aluminum block member of a water-cooled engine, said block comprising a bank of in-line parallel cylinders defined by cast surfaces and each terminating at one end in an opening in a flat head surface of the casting, and a passage for coolant adjacent a portion of each cylinder wall, the passages extending to openings at the head surface and being interconnected with the passage of the adjacent cylinder, said method comprising

• inverting the block with its flat head surface downward and closing the coolant passage openings at the head end of the block without closing the cylinder openings,
• flowing water through the coolant passages from an inlet at the head opening adjacent the cylinder at one end of the bank to completely fill the coolant passages and to pass around each cylinder in the bank in series flow and exit at the upper end of the passage at the opposite end of the bank to maintain the cylinder wall surfaces at a suitable temperature for the application of spray droplets of molten alloy, and
• spraying molten droplets of an alloy onto the surface of the cylinders and solidifying them thereon in an adherent, dense coating of said alloy over selected portions of each cylinder surface without thermal damage or distortion to the casting, the spray pattern being such that overspray exits the cylinder at the head end without coating block surfaces not intended to be coated.