Seznam abstraktů 2024: PLENÁRNÍ SEKCE

Chromium ledeburitic cold work tool steels were developed during the World War I, as a possible substitution for high speed steels. However, it was early recognized that these materials have insufficient hot hardness, and are inappropriate for metal working at high cutting speeds. On the other hand, chromium ledeburitic steels have gained a great popularity in cold work industrial applications, due to their excellent wear resistance and compressive strength. Various steel grades based on the 12%Cr - 2%C concept have been developed over the 20th century in industrial countries such as US, Japan or Europe. But, despite the great popularity of ledeburitic steels in various industrial branches it was found that they suffer from great brittleness and also from their sensitivity to improper heat treatment. Therefore, new steel grades have been developed to overcome these problems. The first alloying concept was focused to increase the toughness. For this purpose, the carbon content was reduced to 1.5%, producing smaller and better uniformly distributed eutectic and secondary carbides. On the contrary, attempts were made to further increase the wear performance of steels, by adding the vanadium to the steels in different amounts. Vanadium forms stable and hard eutectic or primary carbides, which substantially improve the wear performance. However, a common drawback of vanadium addition is that the vanadium-based carbides make it difficult or impossible to manufacture the steels with good or acceptable quality. The main reason is that these carbides are coarse at higher vanadium contents, make the steel brittle and unsuitable for hot forging operations. Therefore, a set of superior-quality powder metallurgy manufactured chromium-vanadium ledeburitic steels has been developed in 1980s and 1990s, and early introduced in the industrial use. The conference paper deals with the basic of alloying concepts of ledeburitic cold-work tool steels, their microstructural development from as-cast to wrought state, whereas the effect of imperfections on tools durability is presented and discussed. Then, heat treatment procedure, including the hardening, tempering and cryogenic treatments is introduced. For each step of the heat treatment the obtained microstructures and related characteristics are shown, and their effects on mechanical properties such as hardness, toughness, wear performance and others are presented and discussed.

Intermetallics, i.e. intermetallic phases, have been included in the metallic materials already since far history. And as the independent materials, they started to be used in middle ages as dental amalgams. In modern world, intermetallics are applied in many industrial sectors, e.g. as the components of the jet engines, as biomaterials for medical use or in electronics. The above mentioned applications and also new prospects for their use, such as intermetallic composites for tools or functionally graded intermetallic materials are presented.