Cutting Tool Coatings

LMT To Present 'World First' Tooling Developments At EMO 2011

At EMO 2011 exhibition in Hannover, the specialised threading division of LMT Fette is to launch XChange which is believed to be the world's first ‘modular' threading tap with a quick-change head. XChange also combines the extended tool life advantages gained from Polaris, LMT's latest high performance carbide coating with the benefits gained from torsional stiffness that is equal to high speed steel (HSS).

With the latest group product launches available from LMT (UK) based in Meriden, a further ‘world first' in thin-film coating technology is also launched at the show. As a result of the company's Protec development, the entire process of thread rolling can now be optimised. Meanwhile, a further chemical vapour deposition (CVD) coating development called TeraSpeed is targeted towards customers looking for higher performance milling.

From its US based Onsrud division, a specialist in machining composite materials, the DFC Compression Mill is released into Europe and a totally new ‘intermetallic' material for higher performance hobbing called SpeedCore is able, through LMT, to perform up to 50 per cent faster than HSS cutters that are produced using the powder metallurgy process.

The XChange modular tap, which has a high silicon content, is most suitable for threading short chipping materials such as cast iron and aluminium. It has internal coolant supply and the carbide thread form head is secured via a patented interface to a HSS shank. This not only reduces the cost of replacement but also helps to reduce tool inventory. When the XChange concept is combined with the advantages of the new Polaris coating, the new threading tap should be able to run at double the speed of more traditional HSS taps with the added benefit of an extended tool life.

The development of the Protec coating by LMT Fette enables the thread rolling process to be optimised due to the lower levels of friction created between the rolls and the component during the form rolling process. In particular the new coating will provide added benefits when threading harder materials above 900 N/mm² with an effective in-process life that should be improved by up to 30 per cent.

TeraSpeed is a totally new CVD applied – AltiN coating developed by LMT's alliance partner Boehlerit that has an exceptional hardness value of 3,500 HV and a high thermal resistance up to 1,000 deg C.Consequently, the cutting performance should be seriously improved compared to the tools that are treated with the most common physical vapor disposition (PVD) coating. For example, in the face of grinding metal removal rates were testing up to 100 percent higher with coated tools TeraSPEED even further gains from improved 200 percent when applied to heavier duty applications corner milling type.

CVD Lays Down the Gauntlet |

: New, high-quality coatings that result in much less wear.

Chemical Vapor Deposition (CVD) is the key technology for creating high-quality coatings that enhance a cutting tool performance. The evolution of tool coatings and processes has dramatically increased tool productivity, and CVD has been one of the major contributors to its growth.

The Sandvik Coromant history in CVD goes back to 1969, when its first coated insert grade was introduced. CG125 had a single titanium carbide coating a few microns thick and resulted in increased cutting speeds and tool life.

CVD is an extremely versatile technology that is used to create thin or thick coatings of everything from hard wear-resistant coatings such as titanium carbonitride, aluminum oxide and diamond to semiconductor products. It is a complementary technique to another widely used tool coating technology — physical vapor deposition (PVD). For tool inserts , CVD enables thick coatings (5-25 μm) of aluminum oxide (Al ), titanium carbide (Tic), titanium carbonitride (TiCN) and titanium nitride (TiN) that offer extremely high wear resistance and make it suitable for conditions where abrasive wear is substantial. By contrast, the thinner coatings produced by PVD processes possess high compressive stresses and are therefore much more suitable for cutting applications where toughness requirements are important. layer to provide chemical and wear resistance. This layer is formed on top of a stack of tough carbonitride and nitride layers that give high flank wear resistance. The insert substrate comprises a base of hard carbides and a cobalt binder phase, and in a zone near the coating the substrate has been depleted on some hard carbide substituents in order to offer improved edge fracture resistance. ) on top, which resulted in excellent wear resistance and coating adhesion. Today’s state-of-the-art technology is an example represented by the GC2025 grade, which is used for stainless steel cutting.

In reality, CVD relates to a range of processes that involve depositing a solid material from a gaseous phase. The essence of a CVD system, in its simplest form, consists of a heated reactor chamber (where the inserts to be coated are placed on trays), a gas delivery system and a vacuum pump system. The pump is used to allow low reactor pressure and for removal of excess and byproduct gaseous species.

Precursor gases, such as aluminum chloride, carbon monoxide, carbon dioxide, hydrogen, nitrogen and titanium tetrachloride, are introduced at preheated temperatures into the reaction chamber.

Handbook of vacuum arc science and technology, fundamentals and applications

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Advanced ceramic coatings and interfaces, a collection of papers presented at the 32nd International Conference on Advanced Ceramics and Composites, January 27-February 1, 2008, Daytona Beach, Florida

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