We can coat the vast majority of tools. Although it is preferable to PVD coat electrically conductive surfaces, nonconductive substrates can also be coated using IVAC’s PVD processes. Coating should be the very last step in tool manufacturing; rework or alteration of coated tools typically negates benefits of the coating. Optimum tool performance can be achieved by observing the following guidelines:
Identify areas to be coated and/or masked. Specify the substrate material and its temperature tolerance (draw or tempering temperature for tools steels).
Parts should be completely disassembled before coating, screws, plugs, inserts removed, internal crevices, blind holes exposed. Cleanliness of crevices and coolant ducts is critical.
Although IVAC’s precision cleaning process removes most contaminants, for the best results, tools for PVD coating should be received free of shop soil, lapping and cutting compounds, lubricants, coolants, and other chemicals. A 1:16 mixture of machine oil and mineral spirit often yields effective cleaning and rust prevention. Alternatively, one can use a water-soluble or light oil based rust inhibitor.
As a rule, the best surface finish yields the highest performance. Surface roughness, burrs and nicks on forming and cutting tools often negate the benefits of coating. Coating quality is unpredictable on EDM’d surfaces.
While IVAC provides metal finishing and polishing services, the best judge of quality and geometry (critical radii, working areas etc.) is the tool owner.
Dress grinding wheels more frequently than for the production of uncoated parts and avoid ‘spark out’. Avoid rubberized or resinoid buffering wheels. Do not sand blast, beadblast, or vapor-hone surfaces to be coated. It is preferable to use silicon carbide wet-and-dry paper for manual polishing. Start with coarse grit; proceed in small steps with finer and finer paper to desired finish. Apply light pressure and change paper frequently. Use plenty of water, change it, and rinse between steps.
Use cadmium-free braze for brazed tools; there should be no crevices and pinholes in the joints. Black-oxided surfaces or those covered with oxide scale cannot be coated.