Janez Marko Slabe

A comparison of tool–repair methods using CO2 laser surfacing and arc surfacing

Abstract The life of loaded machine elements and the vital parts of tools can be successfully extended by systematic maintenance and the timely repair of damaged surfaces. It has been proved that with the regular maintenance of tool parts the cost of the tool in the price of a finished product can be considerably reduced. It is a very economical practise to manufacture certain parts from low-cost, tough structural steel on which a layer of wear-resistant alloy has been surfaced. In such a case the volume fraction of the surfaced layer is usually much lower than 10% of the total volume of the tool or the machine element. In this paper, we report some of our latest results involving comparative studies of repair surfacing on maraging steel and the cladding of common structural steel with a Ni–Co–Mo alloy similar to the maraging steel using a laser process and submerged-arc surfacing. The results are based on micro-structural and micro-chemical analyses of the surfaced layer and are supported by analyses of the micro-hardness and the residual stresses, carried out on suitably adapted flat specimens.

The state of differently heat-treated 12% Ni maraging steel after laser remelting

The paper describes the results obtained in an investigation of laser remelting of specimens made of 12% Ni maraging steel suitable for the manufacture of highly thermomechanically loaded machine parts or tool parts. The aim of the investigation was to establish the state of differently heat treated maraging steel after a laser repair processes including melting of the material. An analysis of the specimens with an optical microscope after laser remelting showed, regardless of the initial condition, a cellular-dendritic microstructure in the remelted track. In the heat-affected zone surrounding the laser-remelted track the microstructure varied considerably also regardless of the initial condition. A microstructure analysis supported by microhardness measurements made it possible to define several microstructural zones or sub-zones in the heataffected zone. The measurement of residual stresses using the relaxation hole-drilling method close to the laser-remelted track was used to study the influence of the initial material state on the residual stresses after laser remelting.

Surface Repair of Tool Made of 12 Ni Maraging Steel by Laser Cladding of NiCoMo Powder

Surface repair experiments with Nd:YAG coaxial laser cladding of NiCoMo maraging powder were made on specimens from maraging steel (EN 10027-2, mat. no. 1.2799). The influences of different modes of laser-beam guidance with various powder mass flows and with different degrees of overlapping of individual traces on the dilution and the repair area were determined. The micro and macroscopic analyses of microsections of fusion zone (FZ), heat affected zone (HAZ) and through-depth microhardness were analysed after cladding and after subsequent solution and precipitation annealing. The microchemical (EDS) analysis was performed at various depths. The residual stresses in the clad face and in the clad toe were determined and compared, using the hole-drilling method.