The industrial applications of the technology of laser-beam surface hardening by remelting grey and nodular graphite cast irons, low-carbon steel, and of aluminium alloys with silicon result in shorter times of heat treatment and lower costs of treatment. A physical-mathematical description of temperature cycles in laser remelting was developed. Such a description of the temperature cycles permits easier and more correct determination of optimum conditions of hardening by remelting taking into account a chosen energy input and a chosen mode of laser-beam guidance. In case of laser hardening by remelting and laser repair welding, the conditions were optimized with special regard to the mode of laser-beam guidance across the workpiece surface in terms of the magnitude of deformations and residual stresses. An expert system was elaborated to optimize the conditions on the basis of the experimental results and by means of the physical-mathematical model of hardening by remelting of grey and nodular graphite iron respectively. With the application of laser-beam surface remelting and alloying of the base metal, i.e., low-alloy steel, with different filler materials such as silicon carbide, Stellite 6, and Stellundum 481, an important improvement of surface properties of the material concerned accompanied by a favourable variation of residual stresses could be accomplished. For laser cutting a particular method of ours was developed to describe the laser-cut quality. Criteria of on-line optimization of the laser-cutting process in terms of the selection of the cutting conditions based on IR radiation from the cutting front were developed. The optimization of laser cutting of low-carbon steel was adapted to meet the needs of MPP Maribor in terms of assuring cut quality and minimum product deformations. It was proved with numerous experiments that it was possible to considerably shorten maintenance services performed on die-casting tools and considerably lower the tool cost in the product price by applying laser repair welding or surfacing and laser precipitation hardening. The development of cored wires for surfacing of maraging steels on low-carbon steel is something new in the field of tool engineering in Slovenia, in particular for casting plants producing die castings of aluminium, magnesium and zinc alloys. The investigations conducted on temperature-time conditions of precipitation annealing of maraging steel and a comparison of the mechanical properties obtained with those of common hot-work tool steels contributed to their introduction in industry, e.g. LTH OL Škofja Loka, DIFA Škofja Loka, Livarna Tolmin, Rotomatika. Quenching processes were studied in case of polymeric water solutions having different concentrations and hardening oils, products of OLMA; therefore, our findings, are of high value to hardening shops in Slovenia. In heat treatment, particularly quenching, the phenomena at the boundary between the workpiece and the cooling medium were studied by making temperature measurements at characteristic points and determining cooling rates. The introduction of non-destructive testing methods, particularly ultrasonic testing, was accompanied by the advancements of a computer-aided system and micro-magnetic methods to describe the states of different ferromagnetic materials such as heat-treatment steels and maraging steels. Adapted micro-magnetic sensors permit testing of different machine parts in the production process. Specimens to be tested were obtained from Kovaška industrija Zreče. It is assumed that this testing method may be automated and then replace the existing classical method of wet magnetic testing with fluorescent magnetic particles where several women workers are engaged. The research of correlations between a microstructure and the surface roughness obtained in fine turning confirm that a fine smooth surface requires a very fine-grained microstructure.