Patent GB-1354262-A (GB)
Title: Process for preparing layers of particulate fillers in a metallic matrix
IPC: B23P5/00
Filed: 1971-04-19
Abstract: 1354262 Coating COMPOSITE SCIENCES Inc' 19 April 1971 [30 March 1970] 25660/71 Heading B3A [Also in Divisions B2 B5 and B6] A layer of a particulate filler in a metallic matrix is produced by applying to a substrate either a layer comprising the particulate filler in an organic binder and a layer containing a metal or an alloy or a self-supporting layer comprising a mixture of the filler, binder and metal or alloy, the metal or alloy having a lower solidus temperature than the filler and when molten wetting the filler particles, heating the assembly to a temperature which is above the solidus temperature of the metal or alloy but below that of the filler so as to decompose the binder and disperse the filler particles in a molten matrix of the metal or alloy, and cooling the assembly to below the solidus temperature of the metal or alloy. Substrates can be a metal, e.g. iron, nickel, cobalt, copper or titanium or an alloy thereof or when the layer of particulate filler in the metallic matrix does not form an adherent coating a low carbon steel which has been treated with an aqueous solution or suspension of magnesium hydroxide and then heated at 300-1000 C. Preferably the matrix is an iron-based, nickel-based or cobaltbased alloy, preferably an alloy containing 5% silicon, 3À5% boron, 15% chromium, 4% iron, 0À6% carbon and the balance nickel. The filler can be an abrasive such as a metal carbide, e.g. tungsten, tantalum, chromium, titanium or silicon carbide, a metal boride, a metal silicide, a metal nitride, diamond, or a mixture of these. The filler can also be another metal or alloy. The layer containing the matrix metal alloy can be in the form of a self-supporting sheet which is either a solid sheet consisting essentially of the metal or alloy or of a sheet of a powdered metal or alloy in an organic binder. Suitable binders for the layer of filler are adhesives such as shellac, rubber cement, benzene solutions of a polymeric acrylate or methacrylate, a polyvinyl alcohol or preferably a polytetrafluoroethylene. Methods of applying the matrix metal alloy and the filler are (1) a powdered matrix metal or alloy can be mixed with binder and the mixture then doctored upon the substrate in a uniform layer, the process then being repeated using a mixture of the filler and the binder; (2) a mixture of the binder, matrix metal or alloy and filler is coated on to the substrate, (3) the layer of filler and layer of metal alloy are applied in the form of self-supporting sheets comprising a binder, each sheet having been formed by mechanically working a mixture comprising either the particulate filler or a powdered metal or alloy and binder and calendaring the mechanically worked mixture into a self-supporting sheet; (4) a layer of filler and a layer of metal alloy are applied in the form of self-supporting sheets which are laminated together, optionally with the use of an adhesive. Various arrangements of the layers on the substrate are illustrated including the arrangement on J-shaped and U-shaped substrates. When the substrate is a clean metal the layer produced is metallurgically bonded to the substrate. Articles which can be coated are turbine blades, tools, workpieces or various structural members. In an example a mixture of 5 volumes polytetrafluoroethylene and 95 volumes of particulate nickel-based alloy was ball-milled, pressed into a sheet and a ring formed from the sheet and placed upon a low carbon steel plate. A mixture of 5 volumes of polytetrafluoroethylene and 95 volumes of particulate tungsten carbide was ball-milled, pressed into a sheet and a circular ring formed from the sheet and placed on top of the first mentioned ring and the assembly heated at 1070-1080 C. in a furnace having a hydrogen gas purge to produce a tungsten carbide filled metal ring metallurgically bonded to the steel plate.