GB1273691A - Electric arc or plasma hard facing of metals - Google Patents

Abstract

1,273,691. Fusion welding. LA SOUDURE ELECTRIQUE AUTOGENE PROCEDES ARCOS, S.A. 16 Jan., 1970 [6 Feb., 1969], No. 2267/70. Heading B3R. A process of overlaying e.g. hard-facing, a metal workpiece comprises coating the workpiece with a material capable of forming a barrier layer to inhibit dilution of the facing metal by the base metal, and finally applying the facing metal by an electric arc or plasma torch device, this step being accompanied by melting (or remelting) of the material forming the barrier layer. Materials referred to as barrier layers include cobalt, chromium, tungsten, molybdenum, the carbides of chromium, tungsten and molybdenum, zirconium oxide and titanium oxide. Methods of application of the barrier layer include flame spraying, plasma spraying, electroplating or application as an emulsion, containing possibly also a binder and adhesive. The overlay metals include those known under the Registered Trade Marks Stellite and Inconel as well as stainless steel. The facing metals may be applied by a series arc procesi in which the arc is struck between two consumable electrodes 3, 4 arranged symmetrically to the plane of the workpiece. Alternatively one of the electrodes may be of graphite or tungsten, in the latter case optionally thoriated or zirconated and with argon shielding. Where the barrier layer is of one of the oxides mentioned the arc may be struck by a high-frequency discharge. In an example a powdered alloy of 1% Carbon, 28% Chromium, 5% Tungsten and the balance Cobalt was applied by plasma spraying under a nitrogen atmosphere and a hard-facing layer applied using electrodes of the following composition:1% Carbon, 31% Chromium, 5À5% Tungsten, balance Cobalt.