The aim of the present investigation was to examine the possibility of reducing lubrication and replacing expensive tungsten carbide material in blanking/piercing through introduction of hard tool coatings. Results show that hard PVD coatings can be successfully used in blanking/piercing applications, even on softer tool steels, thus leading to reduced friction and wear as well as to lower costs of the tool. However, preparation of the substrate material and good coating to substrate adhesion are crucial. On the other hand, even with the use of low friction coating (DLC) stamping force exceeds critical value under dry friction conditions and leads to tool failure. Therefore, at present oxidation and temperature resistant hard coatings can give improved wear resistance of stamping tools, but elimination of lubricants in blanking and piercing processes is still not feasible.
COBISS.SI-ID: 855466
The impurities sulphur, phosphorus, lead, bismuth, tin and antimony affect the hot workability of stainless steels. In this study, the authors show that sulphur and lead segregate to phase and solidification grain boundaries, where cracks appear during hot deformation. The workability was tested by the hot rolling and hot bending of industrial and laboratory steels.
COBISS.SI-ID: 855978
A precise knowledge of the level and distribution of residual stresses that exist in engineering components is necessary for an accurate design and prediction of a component’s fatigue resistance. However, measurement of residual stresses is not always possible. Therefore, other methods for residual stress evaluation and prediction are required. Results of this investigation show that residual stress level and depth in plasma nitrided tool steel increase with nitriding time and temperature. On the other hand, experimental data indicates that the residual stress distribution in plasma nitrided tool steels can be determined on the basis of microhardness depth distribution. Furthermore, the residual stress level can be extrapolated by using reference residual stress data and genetic programming. In this way the residual stress level and distribution can be obtained even for components where measurement is not possible.
COBISS.SI-ID: 1980411