Tailored tool solutions for the machining of new materials
Manufacturers often seek to improve the energy efficiency of their products, e.g. vehicles, by increasing the strength of the materials used or by integrating composite materials with high hard phase content. This, in turn, results in higher loads on the tools used for machining these new materials.
As a consequence, the tools must meet increasing demands in terms of hardness, toughness and wear resistance. Modern tools are therefore often made from advanced composites. Hard metals, which demonstrate a high degree of hardness and sufficient toughness, are ideal substrate materials for wear-resistant hard coatings. The substrate material must be sufficiently hard to prevent it from plastically deforming upon contact with the workpiece, while the coatings are designed to protect the tool from wear due to adhesion, abrasion or oxidation.
Hard metals are extremely resistant composites with a ceramic hard phase and a metallic binding matrix, providing a unique combination of hardness, toughness and resistance to wear. The stress required to deform a hard metal is up to twice that for the strongest steels currently available. The high resistance against plastic deformation enables higher tool load and opens up new applications for hard metal tools.
Knowledge-based tool design
The cutting edges of tools are exposed to high temperatures as well as mechanical and tribological loads. Local temperatures and mechanical stresses are the decisive influencing parameters for the substrate material. Numerical simulations of the cutting process provide the basis for a detailed analysis of the temperatures and stresses within the tool. Many tools show plastic deformation near the cutting edge, which in turn leads to the build-up of residual stress. In order to describe these phenomena quantitatively the physical and mechanical properties must be known in detail, i.e. as a function of temperature and strain rate.
The Materials Center Leoben has developed sophisticated testing methods for determining the mechanical material properties of hard metals over recent years. These methods are used in numerical models to predict how the hard metal substrate will react to stresses occurring during the cutting process.
Impact
The combined experimental and numerical development approach provides new findings for a knowledge-based design of cutting tools and enables substantial increases in productivity, new processes and new applications. The new findings have already produced positive results in selecting suitable hard metal types for specific cutting applications.