It is important to understand some fundamentals of high-performance tool coatings:

1. All similar coatings are not alike. The performance of a TiN/TiCN/TiAlN-coated tool from one vendor may perform significantly different than a TiN/TiCN/TiAlN-coated tool from another vendor. Kennametal conducted independent tests of tools from the same lot and coated by different vendors, including ourselves. The results revealed a performance spread of 10X when tested in identical test conditions. In extreme cases, a drill coating from one vendor may yield 300 holes while another's coating will yield 3,000 holes! Consistent day-to-day and month-to-month performance is critical for predictable results.
2. Coatings development is an ongoing process at Kennametal. It is constantly evaluated and improved to yield higher productivity and consistency on tools and workpiece materials. Kennametal's Research and Development department updates recommendations and changes in both SFM and IPR about once a quarter, based on ongoing improvements to our coating process.
3. Surface feet recommendations are vital. To achieve any benefit from high-performance coatings, these coatings must be run at significantly higher speeds than other coatings. If coated tools are run at parameters other than those recommended, they can be counter-productive. Follow the manufacturer's recommended starting points (which are typically conservative) and work upward from there.

Kennametal coated tools set the standard for the highest possible performance available in the marketplace.

Technical Tip #34 - Coatings for Cutting Tools

Following are Kennametal's current recommendations for taps in various materials. They are listed in order of preference. Those in parentheses should be viewed as alternatives, but are not in order of preference. Maxi #1 is Kennametal's designation for nitride.

Remember to increase SFM by 50% for TiN and TiCN, and 100% for TiAlN.

• Carbon steels 1010, 1045:  TiCN, TiN, (oxide, oxide over nitride)
• Alloy steels 4140, 8620: TiCN, TiN (oxide, oxide over nitride)
• Tool steels A2, D2, H13:  TiCN, TiN (TiAlN, oxide, oxide over nitride)
• 300 Stainless 304, 316: TiCN, TiN (oxide, oxide over nitride)
• 400 Stainless 414, 440: TiCN, TiN (oxide, oxide over nitride)
• PH Stainless 15-5PH, 17-4PH: TiCN, TiAlN (TiN, oxide, oxide over nitride)
• Cast iron, ductile: TiCN, TiN (oxide, oxide over nitride, Maxi #1)
• Cast iron, gray class 20-50: TiCN, TiN (oxide, oxide over nitride, Maxi #1)
• Aluminum, wrought 1100, 2024: CrN, Maxi #1
• Aluminum, silicon cast 319, 360, 380: (TiCN, Maxi #1) TiN, CrN
• Copper, brass, bronze, zinc, magnesium: CrN, Maxi #1
• Titanium, pure CP Ti: Maxi #1, CrN
• Titanium, alloy Ti-6AL-4V: Max #1, (TiN, TiCN, TiAlN, CrN)
• Nickel-based alloy monel, Inconel: TiCN, (TiN, TiAlN, CrN) (Maxi #1, oxide, oxide over nitride)
• Iron-based alloy A-286, Incoloy: TiCN, (TiN, TiAlN) (Maxi #1, oxide, oxide over nitride)
• Cobalt-based alloy haynes: TiCN, (TiN, TiAlN, CrN) (Maxi #1, oxide, oxide over nitride)
• Plastics, soft and abrasive: TiCN, (TiN, Maxi #1) CrN
• Graphite: TiCN, (TiN, Maxi #1) CrN

Technical Tip #35 - Coatings for Taps

Typically when drills or end mills are resharpened, the coating is removed only from the clearance or flank area of the tool. When resharpened this way, there is still coating protection on the rake face of the tool. Tool life typically decreases by 30% or more but is still much better then an uncoated tool.

If the regrind process removes the coating from the rake face, the tool will perform no better than an uncoated tool. As a general rule, tools should be recoated after resharpening to restore the full protective effect of the coating.

If good metal removal rates are the goal for a reground, not recoated, tool, then speeds and feeds can be left very close to coated-tool parameters.

If maintaining tool life is the goal, then reduce speeds and feeds by 20% to 30% to achieve results close to those of coated-tool life.

Additionally, after multiple recoats, drills, reamers, and other close-tolerance tools can become oversized due to the layering effect of the multiple coatings. In these cases the tools can be stripped, resharpened, and recoated to restore the tool to original specifications.

Technical Tip #37 - Resharpening Coated Drills

PVD TiN coatings are the primary general-purpose coating for end mills, but TiCN and TiAlN are becoming popular in use. Common questions for milling applications include when to use these advanced coatings, and at what speeds to run them.

TiCN is a harder coating than TiN and has good abrasion resistance. It is very good in milling applications for steels, stainless steels, and non-ferrous materials. End mills coated with TiCN should be operated at speeds up to 50% higher than uncoated end mills.

TiAlN is a high-performance coating for all material types. It is about the same hardness as TiCN but will maintain that hardness at a much higher cutting temperatures. This makes TiAlN very effective in high-temperature alloys, high-speed machining, and dry milling applications. End mills coated with TiAlN should be operated at speeds up to 100% higher than uncoated end mills.

The right coating can yield substantial time and cost savings, but those savings are in proportion to your machine's ability to achieve the high speeds required by those coatings.

Technical Tip #63 - Maximizing End Mill Coatings

1.0  Aluminum-oxide based cutting ceramics
       1.1 Oxide ceramic (white)
             1.1.1 For cast iron applications
       1.2  Black ceramic
             1.2.1 For cast iron applications
             1.2.2 For hard-turning applications
       1.3  Whisker reinforced
             1.3.1 For cast iron applications
             1.3.2 For hard-turning applications
             1.3.3 For super-alloy applications
2.0 Non-oxide based cutting ceramics
       2.1  Sialon
             2.1.1 For cast iron applications
             2.1.2 For super-alloy applications
       2.2  Silicon nitride
             2.2.1 For cast iron applications

Technical Tip #147 - Classification of Cutting Ceramics