Why do PVD coatings improve performance?
Low deposition temperature
PVD thin film coatings can be deposited at temperatures below 500 deg.C. This allows substrates such as bearing steels and titanium or aluminium alloys to be coated. This would not be possible using chemical vapour deposition, CVD. The coating temperature can even be reduced to such a level that polymers can be coated.
Magnetron sputtered coatings follow the exact surface roughness of the substrate material. If a fingerprint was present before coating you will see it after coating. Smooth coatings are vital for applications such high precision forming
PVD coatings are deposited while under concurrent ion bombardment. These energetic ions allow the deposition of dense, hard films by supplying the sputtered neutrals with sufficient energy to find a suitable nucleation site and inducing high compressive stress. PVD coatings with a hardness of 1000-4000HV can be deposited with this technique, approximately 5x the hardness of high speed steel.
PVD coatings can be deposited that are resistant to all forms of wear. In machining for example substantial reductions in the following wear mechanisms are observed:
Problem: Crater wear (chemical interaction between the tool and the work piece).
Solution: Stable coatings that do not readily chemically react.
Problem: Flank wear – abrasive wear by hard constituents of the work piece.
Solution: Hard coatings
Problem: Built-up at the edge – welding of the work piece material to the tool tip which may detach along with part of the tip.
Solution: Low friction coatings that reduce heat generation and the formation of solid solutions.
Problem: Depth of cut notching – oxidation of the tool material with some abrasion from the edge of the chip.
Solution: Coatings can be deposited that resist oxidation up to 1000 deg.C.
Problem: Thermal cracks – produced by temperature gradients in repeated heating and cooling in interrupted cutting
Solution: Low friction coatings that reduce heat generation.