The first market to explore is the tool coating market. Tool life improvement is the result of several upgraded functionalities, depending on the use of the tool. Hardness, temperature resistance and the contact between the tool and the material that needs to be cut or formed can be positively influenced. In some cases coated tools can realize a tool life that is ten times longer than uncoated tools. One important trend that is influencing tool coatings is the cutting of lightweight materials. In the automotive industry, lightweight materials are being chosen because of less fuel consumption and less CO 2 emissions. As a result, materials such as aluminium, magnesium and carbon reinforced plastics are gaining importance. Apart from the reduced weight, these materials have one thing in common - they have the tendency to stick to the cutting tool resulting in shorter tool life. This trend has stimulated the development of DLC coating, which is a hydrogen-free diamond like carbon coating with a low coefficient of friction.
Crossover Tribological Applications
It is a practical example of a crossover development originated from tribology and applied in the tool coating market. In tribological applications this hydrogen-free diamond like carbon (DLC) coating is used to reduce wear and friction. Applied to the tool industry, DLC coatings have proven to be extremely suitable for cutting lightweight metals and fibre reinforced plastics that tend to stick to the tool. A ta-C coating for tools is much thinner with a typical layer thickness of 0.5 µm. With DLC coating the tool life can be significantly increased. The coatings are deposited with arc deposition technology using circular shaped arc cathodes, guaranteeing a strong adhesion of the coating itself.
In every industry cost efficiency is a driving factor that needs constant attention. The tool industry is no exception. The cost of the tool coatings is only a small part of the total cost of a tool, but because the coating process is positioned at the end of the production line, it is very important that the coating is of high quality. Therefore in tool coating, reliability is as important a factor as costs. Upon development of a new circular arc technology for depositing nitride coatings, companies will be focused on making many cost-of-ownership factors more efficient than ever before. Characteristics will be short batch times, high target efficiency and smooth coatings that need minimal post-treatment. A shift in benchmark coatings is happening now that proven technology has been expanded with a highly functional AlCrN coating for hobs used in gear cutting.
The awareness of sustainable production methods becomes more and more mainstream, also in the tool industry and related fields up and down the supply chain. Important factors here are the future scarcity of raw materials, energy consumption, renewable energy, toxicity of materials and recycling in biological or industrial circles. In the tool industry some answers to these challenges are found in higher tool speed and feed rates. Some coated tools can achieve not only longer cutting lengths, also a larger depth of cut per contact, saving time and energy along the way. The feed rate of meters per minute is deciding. Another trend that is driven by sustainability as well as cost efficiency is less use of cooling liquids. Dry cutting or minimum quantity lubrication (MQL) are trending, which leads to increased temperatures of the tool cutting edges and hence a need for improved oxidation resistance.
The trends in the tool industry are all related. The trends for cost efficiency and environmental awareness lead to lower use of cooling fluids, which in turn leads to higher temperatures during cutting. The industry answers with a different choice of component materials and coatings that can withstand the high temperatures. Component materials such as titanium (Ti) and nickel (Ni) alloys are difficult to cut because of their sticking tendency and toughness, but ta-C coating will not bring any solutions here because of its operating temperature maximum of around 500 °C. Nitride coatings are therefore a better solution. They can function at operating temperature levels of up to 1100 °C or even 1500 °C (Table 1). Application directed development has been done to adapt the coatings made with circular arc technology to specific applications, such as high speed milling and roughing finishing. For cutting titanium the TiAlN coating produced with specific circular arc technology can give excellent results. Furthermore there are developments regarding silicon-containing nanocomposite coatings and fine-tuning AlTiN for specific applications.
The trends in tool, tribological, and decorative markets provide many opportunities for PVD and PACVD coating technology. A great deal of research and development is done by teams consisting of coating equipment manufacturers, universities and the industry to improve and optimize coatings. Extra attention should be given to the crossovers between different markets. Experiences from one application can give a lot of input for further development of technologies and coating solutions for another application, sometimes in a completely different market. Crossovers can speed up developments significantly.