A family of extremely fine-grained alloys are used to make coatings or
free-standing bodies having desirable properties for use as a
heat-resistant and wear-resistant material. In an illustrative
embodiment, the alloys are comprised of a multiplicity of alternate,
microcrystalline or nanocrystalline films of tungsten metal and tungsten
compound. The tungsten compound film may be comprised of a tungsten
carbide or a tungsten boride. The tungsten films are the primary films.
Their desirable characteristics, in addition to their very fine
crystalline habit, per se, are the high strength, high hardness, high
resilience, and high fracture energy which these fine crystallites
foster. They may be manufactured by a chemical vapor deposition process
in which reactive gas flows are rapidly switched to produce alternate
films with abrupt hetero-junctions and thereby to produce the useful
micro-crystalline habit. The unique synthesis method allows effective
control of critical flaw size. The structure is such that the primary
films may be made sufficiently thick so as to assure some desirable
ductile behavior, but sufficiently thin so as to have high yield strength
by dint of their microcrystalline size, and as to limit the size of any
flaws. The secondary films are made of enough thickness to prevent the
epitaxial growth from one primary film to the next-deposited primary film
and thin enough so that they can not contain a flaw of critical size. In
addition, the exterior surface of any body made by this method may have a
sufficiently smooth surface that the strength of the body is determined
by the bulk properties of the material and not by surface flaws.