Meaning
Physical vapor deposition creates a transition metal nitride layer on tool steel substrates to elevate hardness and reduce friction during high speed forming. This crn coating deposits a stoichiometric compound of chromium and nitrogen in a vacuum chamber through a reaction between vaporized metal ions and nitrogen gas. It provides a superior thermal barrier and oxidative resistance compared to standard titanium nitride alternatives when polymers contain glass fillers or abrasive flame retardants.
Hardness values for this metallic ceramic typically reach twenty gigapascals.
Tooling Application
Specialized chemical stability prevents molten resin from adhering to cavity surfaces during high pressure injection cycles. Process engineers select this crn coating to eliminate surface pick up and galling that often occur when processing crystalline resins or high glass fiber loadings. Friction reduction allows for lower ejection forces during parts removal from deep cavities or complex slides.
Moulders gain stability across production runs because the layer maintains its thickness and geometry despite repetitive mechanical contact with abrasive particulate matter.
Operational Efficiency
Consistent film thickness across complex geometry protects core pins from excessive wear when tolerance windows remain narrow. The low coefficient of friction helps minimize cycle times by allowing smoother flow through gates and runners. Regrind materials that possess metallic impurities or dust create less damage to tool geometry when surfaces exhibit this level of hardness.
Maintenance intervals lengthen because the surface resists the chemical degradation usually caused by halogenated resin additives or high heat exposure.
Technical Boundary
Maximum temperature exposure limits the utility of this layer before the chromium nitride undergoes phase decomposition into softer metallic constituents. Atmospheric oxygen triggers this oxidation process at temperatures exceeding seven hundred degrees Celsius in continuous duty. Tooling designers specify the surface treatment according to the anticipated thermal load of the melt rather than simple abrasion resistance alone.
This treatment effectively halts mechanical wear but fails to stop the chemical leaching of additives from specialized thermoplastic compounds.
