The Requirements Of The PVD Coating For The Surface Of The Workpiece

- May 19, 2018-

The surface condition of the workpiece or tool has a decisive influence on the performance of the coating, and is a prerequisite for the quality of the perfect coating. In order to have good quality coated workpiece, the workpiece needs to be ground or polished and preservative treatment for transportation.

1. The ground surface should not be lightly cracked, oxide skin or re-hardening burn.

2. The coolant used during grinding cannot contain any calcium sulfonate, boron or iodine compounds, or silicon containing defoamers.

3. The grinded surface, surfaces ground by grindstones, polished surface, or plated surface must be free of abrasives and residues.

4. The blade must be free of burrs to prevent breakage during the first use.

5. In the EDM (Electrical Discharge Machining) process, multiple surface treatment paths are recommended to reduce the formation of "white layer".

6. The surface must be shiny metal. A rusted surface, a brown lighted surface, a steamed blue surface, or a similarly treated surface cannot be coated.

7. Blind holes and internal threads must be free of hardened salt and other contaminants.

8. Chippings, waxes, tapes, oil paints and other non-metallic impurities grinding powders, detergent residues, fingerprints and the analogues must be removed from the workpiece.

9. The welded joints and brazed joints must be free of air holes, fluxes, and cadmium compounds.

10. The workpiece should be demagnetized.

The average roughness Rz of the functional surface to be coated can be used as the first gauge indicator. The value should be in the same order of magnitude as the thickness of the coating. When the surface roughness is high, the local coating pressure is too high, so the coating is stripped and the risk of coating fracture at the peak of roughness.