Saving in metal, corrosion and wear control of machine parts are the
problems of increasing priority. Conventional constructional materials
are unable to provide re- liability and durability of equipment under
conditions of increased working speeds and loads, aggressive medium
attacks and elevated temperatures. Solution to these problems involves
change in properties of the surface layers of products, in the first
instance, by means of depositing functional coatings on machine parts.
Rela- tive simplicity of the process and. practically unlimited
possibilities of varying properties of coatings have resulted in their
wide usage in machine building and transport industry, instrument
engineering, radio electronics and other industries. Coating provides
means for enhancing constructional strength of steels and al- loysl. It
makes possible a combined method when one group of dislocation
mechanisms is used for bulk hardening (grain refining, creation of
stable sub- granular dislocation structures), while the working surface
is hardened through other mechanisms (dislocation density increase,
separation of excess phases, etc). Combined hardening saves valuable
alloying components and provides reduction in metal consumption of
machines and constructions. Coating allows manufacturing new composites
that combine high durability (fatigue resistance, wear resistance) with
sufficient reliability (fracture toughness); enhancement of operational
stability of machine parts and tools as compared to stability attainable
using conventional heat treatment methods; restoration of worn surfaces
and, consequently, reduction in demand for spare parts.
