GB495311A - Improvements in or relating to the manufacture of articles with protective or resistant surfaces or surface parts - Google Patents

Abstract

An article having a surface or part thereof consisting of carbide of one of the metals, chromium, tungsten, vanadium, titanium, tantalum, molybdenum or uranium, hereinafter termed "heavy metals" is produced by applying the metal in finely divided form to a mould, e.g. of steatite, carburizing the metal and sintering the carbide formed, and then casting a carrier metal into the mould to form the remainder of the article; the article is separated from the mould after cooling. The heavy metal may be deposited by electrophoresis from a suspension in water or in an alcohol or ketone. The mould may be previously rendered conducting by a graphite layer; this may be covered with a thin layer of a metal of the iron group applied by cathode dispersion or electrolysis. The carbon necessary for carburization may be supplied by heating the mould with its heavy metal layer in iron, nickel or cobalt carbonyl vapour whereby metal is also deposited. The form is then heated in an inert or reducing atmosphere to a temperature slightly below the melting point of the iron group metal whereby carburization and sintering are simultaneously effected. The carbonyl treatment is preferably carried out at reduced pressure, which may be varied, together with the temperature, so that the vapour is alternately above and below the decomposition point. Alternatively carburization may be effected by heating the heavy metal layer in a carbon-containing gas or vapour such as acetylene or coal-gas, or by applying reactive carbon in admixture with the heavy metal or in alternating layers therewith in stoichiometric proportions and thereafter heating. The materials be applied by spraying. A layer of copper may be deposited on the sintered carbide layer before casting aluminium thereon; in other cases the carrier metal may be cast directly on the carbide. Casting is preferably carried out in vacuo, an inert or reducing gas being admitted before solidification has taken place. Specification 486,620, [Group XXII], is referred to.