Hard coatings for wear resistance are commonly used in the cutting tool industry. The application of such coatings can be performed by a number of methods:
- Arc evaporation (e.g. Sulzer, Ionbond, Hauzer)
- Thermal evaporation (electron beam) (e.g.Oerlikon Balzers, TecVac)
- Magnetron sputtering (e.g. Cemecon, Hauzer, TCL)
All of the above processes are used in combination with a negative bias imposed on the substrates or cutting tools, and each also has a reactive gas element. So essentially this is an 'ion plating' process. The most commonly used industrial method is Arc evaporation due to its robust nature and high levels of ionization in the metal flux. Sputter coating is also widely used and produces a smoother layer than Arc (no nodules), but sputter coating requires some means to provide additional ionization. This additional ionization can be provided direct from the source by unbalancing the magnetic field. Gencoa have been developing such process and magnetrons for tool coating for the last 12 years and the experience of our staff even pre-dates the beginnings of Gencoa. Gencoa are hence in a position to provide the complete solution:
To deliver an optimized hard coating unit a wide variety of elements need to be carefully understood and designed correctly. There are two options: purchase a complete turn-key facility from an established manufacturer or purchase the key components and integrate in the correct way. If the component route is taken the process routines need to be implemented to create the balance of tool adhesion, hardness and toughness. Gencoa can provide and combine all elements of these components to ensure the highest chance of a successful solution.
A key element to a successful sputter-based hard coating process is the reactive gas control. The Speedflo unit provides a high speed gas control to optimize rates and enable the changing of the setpoints during the coating process. This provides a high degree of stability and a high rate process. Pre-programmed routines are available to be loaded into the Speedflo unit that can create the graded nature of the layer structure. The other essential element is to provide enough ionization for a dense coating structure without the need for too high a substrate bias (high bias leads to brittle coatings). Gencoa have experience of designing machine geometries that can create the right process environment. Without the required level of ionization, a successful layer structure will be hard to create.
The usual method of reactive gas feedback control is to collect a light signal from the plasma as the indication of the balance of metal to reactive gas, a method known as plasma emission monitoring (PEM). Gencoa have now developed the Speedflo unit to control a typical hard coating processes direct from the target voltage only. This highly desirable solution avoids the cost and inconvenience of fibre-optics located within or on the process chamber.