KYOCERA Hardcoating Technologies
KYOCERA Hardcoating Technologies
Before any PVD (Physical Vapor Deposition) coating is applied, the condition of the substrate plays a critical role in determining the final coating performance. Factors such as grinding, polishing, brazing, and even rust protection can affect coating adhesion, hardness, and wear resistance.
This guide outlines best practices for substrate preparation to ensure optimal adhesion and coating durability for cutting tools, industrial components, and parts used in high-performance environments.
Improper surface preparation can result in poor adhesion, softening of the substrate, or contamination that weakens the coating bond. Whether you’re coating carbide cutting tools, high-speed steel parts, or precision-machined components, these steps help protect your investment and enhance performance.
1. Avoid Excessive Heat During Grinding
Overheating during grinding can cause stress cracks or anneal the surface, especially on high-speed steel. Oxidation (grinding burn) can create a barrier that prevents coating adhesion. Use proper coolant and grinding parameters to prevent this issue.
2. Prevent Cobalt Leaching in Carbide
Cobalt leaching from cemented carbide leads to poor coating adhesion. This can result from improper coolant chemistry, aggressive cleaning chemicals, or high humidity. Ensure grinding fluids are well-maintained, and avoid overexposure to moisture.
3. Remove Burrs Before Coating
Overheating during grinding can cause stress cracks or anneal the surface, especially on high-speed steel. Oxidation (grinding burn) can create a barrier that prevents coating adhesion. Use proper coolant and grinding parameters to prevent this issue.
4. Ensure Proper Heat Treatment of Steel
PVD coating typically occurs at around 950°F. Steel components should be heat treated at least 50°F higher than the coating temperature to avoid annealing during the process. This can soften the substrate.
5. Watch Out for Surface Treatments
Surface treatments like black oxide or certain nitriding processes can interfere with coating adhesion. If present, these layers may require removal or further processing prior to coating.
6. Use Caution When Grit Blasting
Grit blasting helps prepare the surface but must be done correctly. Avoid glass bead blasting if possible. If used, keep pressure below 30 psi. Always use clean, contaminant-free media and replace it regularly.
7. Use Silicone-Free Polishing Compounds
Avoid polishing compounds that contain silicone, as they can leave behind residue that prevents proper coating adhesion. Use water-based polishing compounds instead of oil-based options.
8. Follow Best Practices for Brazed Parts
Brazing materials must be stable at high temperatures. Use high-temperature brazing alloys that are free from lead, cadmium, or zinc. These elements can vaporize or melt during the coating process, leading to coating defects or weakened joints.
9. Choose Rust Inhibitors Carefully
While it is acceptable to apply a light, water-soluble oil to prevent rust, avoid oils that leave a protective film or residue. These can be difficult to remove and may reduce coating performance.
Each application is unique. Getting the surface right the first time can save significant time and cost in rework or failed parts.
If you’re not sure about how to best prepare, our team can help. Select the option below to contact sales and support, and check out the following FAQs.
Q: What should I do before PVD coating?
A: Clean the surface, remove burrs, and make sure it’s free of oil, rust inhibitors, or surface treatments that affect adhesion.
Q: Why won’t my PVD coating stick?
A: Poor adhesion is often caused by cobalt leaching, oxidation, surface contamination, or improper heat treatment.
Q: Does heat treatment matter before coating?
A: Yes. Steel should be heat-treated above the PVD process temperature (around 950°F) to avoid softening during coating.
Q: Can I coat over black oxide or nitriding?
A: Not directly. These treatments can interfere with coating adhesion and may need to be removed first.
Q: What happens if I leave burrs on the part?
A: The coating will cover the burr, and when it breaks off in use, it leaves a weak spot or void in the coating.
Q: Can grit blasting hurt the surface before coating?
A: Yes. Use the right media and pressure. Glass beads at high pressure can damage the surface or embed contaminants.
Q: Is it okay to use silicone polishing compounds?
A: No. Silicone can leave residue that prevents adhesion. Use water-based, silicone-free compounds.
Q: What’s cobalt leaching and why does it matter?
A: Cobalt leaching from carbide weakens the surface and causes poor coating adhesion. Avoid harsh chemicals and monitor humidity.
Q: Can I coat brazed tools or parts?
A: Yes, but use high-temperature, lead-free brazing compounds. Metals like lead, cadmium, or zinc can vaporize during PVD and ruin the joint.
Q: Will rust inhibitors affect coating adhesion?
A: Some will. Use a water-soluble oil that leaves no residue. Avoid rust preventatives designed to leave a protective film.
UNITED STATES
KYOCERA Hardcoating Technologies
220 Marc Drive
Cuyahoga Falls, Ohio 44223
USA
UNITED KINGDOM
KYOCERA Hardcoating Technologies – Europe
11 Ashville Way, Wokingham,
Berkshire RG41 2PL
United Kingdom
