Coating metals and other material with stable metal oxides

摘要

Coatings of heat-stable metal oxides or mixtures of such metal oxides alone or combined with other materials to form heat-stable substantially wholly metal oxide mixtures are produced by feeding a rod of said oxide into a flame hot enough to melt it, atomizing the molten oxide with a blast of gas as it is melted, and spraying the atomized molten oxide on to the material to be coated, e.g. metal, graphite, ceramic or sintered oxide. The rod of oxide to be spray coated may be formed by sintering. As shown, a metal spray gun having a flexible shaft drive 14 from a motor 10 drives through two sets of worm gearing 20, 22 a pair of rubber-covered rollers 26, 27 which feed between them a sintered metal oxide rod 30. The rod is melted by an oxy-acetylene flame supplied from hoses 32. 33 and the liquid oxide is atomized by an air blast from hose 31. Prior to coating it is preferable to sandblast the receiving material especially if this is iron or steel. Molybdenum gas turbine blades may be coated by this method with stabilized zirconia containing 3 to 6 per cent lime as described in U.S.A. Specification 2,535,526 to resist oxidation in use, and similarly refractory graphite parts for guided missiles and rockets may be coated with alumina, while moulded alumina articles may be rendered less porous by coating with alumina. Suitable oxides for use in the invention are those of aluminium, barium beryllium, calcium, cobalt, magnesium manganese, molybdenum, nickel, niobium, strontium, tantalum, thorium, tin, titanium, uranium, vanadium, zinc, zirconium and minerals comprising combinations of these oxides, such as the spinels including those of chromium and iron (except magnetite), with or without other oxides, such as of antimony as in lewisite and of lead as in uraninite, and miner proportions of other substances such as helium, rare earths as in thoriahite, and even silicon as in emery or halogens.ALSO:A moulded crucible of pure crystalline and/or amorphous alumina, optionally together with 1 per cent bentonite, is spray-coated with molten alumina to render it non-porous.ALSO:Mixtures of heat-stable oxides of aluminium, barium, beryllium, calcium, cobalt, magnesium, manganese, molybdenum, nickel, niobium, strontium, tantalum, thorium, tin, titanium, uranium, vanadium, zinc, and zirconium, especially as minerals, and one or more minerals containing one or more of said oxides with iron oxides such as chromite, ilmenite, and tantalite or even emery, are melted and spray-coated on to metals such as molybdenum, ceramics such as alumina, or graphite to provide wear-resistant, refractory surfaces.