A process for producing bulk alloys as engineering materials is carried out in a vacuum vessel and includes evaporating the constituents and depositing them upon a collector in such a way that the deposit is laid down in successive layers. This is achieved by arranging that the collector and the source or sources from which the constituents are evaporated move relative to one another. Preferably the source or sources are stationary and the collector is moved relative thereto. In this way it is possible to achieve the high evaporation and deposition rates necessary to economical production of alloys by deposition of the constituents from the vapor phase and also faults in the deposit such as columnar growth and intercolumnar porosity may be substantially eliminated. Apparatus in which this process may be carried out is described.
A method of producing metal coated diamond particles in which the coatings are strongly bonded to the diamond particles characterised in that a layer of an alloy consisting of a major proportion of a metal such as copper, nickel or iron and a minor proportion of a carbide-forming metal such as titanium, chromium or vanadium is applied to the uncoated particles and then the coated particles are heat treated to a temperature of between 500.degree.C and a temperature just below the melting point of the alloy for a time sufficient to enable a bonding carbide layer to form at the alloy/diamond interface, the steps being carried out in a non-oxidising atmosphere. The invention further provides diamond particles having bonded thereto an alloy comprising a major proportion of nickel and a minor proportion of a carbide-forming metal such as titanium, chromium or vanadium, the bonding being achieved by means of a carbide layer, which is preferably continuous, at the alloy/diamond interface.
