Chemical Vapor Deposition (CVD) is a heat-activated process which relies on the reaction of gaseous chemical compounds with suitably heated and prepared substrates including carbides and tool steels.
The Bernex CVD process has been developed in the early 1970s and has been continuously improved over the years in order to respond to ever more demanding market requirements in terms of the coating process, structures and combinations.
The typical process temperature for CVD coatings is between 900กใ C and 1050กใ C for high temperature CVD and between 720กใ C and 900กใ C for the Bernex? MT CVD process.
Items Typically Coated
The most common items coated are carbide inserts, punches, metal forming tools and extrusion dies, however applications also exist for various components that are subject to abrasive or corrosive environments. In terms of substrate materials, carbides, tool steels, Inconels, ceramics and graphite can be coated, however due to the high temperature of the process, most steels will require a post coating heat treatment.
Coatings Typically Deposited
The coatings typically deposited are TiC, TiCN (both high temperature and moderate temperature), TiN and alpha and kappa aluminum oxide (Al203). The coatings are almost always deposited as multi-layers such as TiC / TiN or TiCN / Al203 or TiCN / Al203 / TiN where the layer combination is engineered to meet the demands of a specific application such as milling cast iron or interrupted cutting of difficult to machine materials.
Coating thickness typically range from 5 to 12 microns, but in some cases coatings can be as thick as 20 or more microns with total cycle times ranging from 8-24 hours.
Advantages of the process:
Extreme toughness of coatings
High loading capacity of certain tools (but long cycle times)
Items to be coated do not require rotation within the retort
Possible to coat complex geometries, including certain inner diameters
Excellent coating uniformity, independent of part geometry