Effect of laser-remelting of surface cracks on microstructure and residual stresses in 12Ni maraging steel

The paper presents the results of a study on possible application of laser-remelting to repair of narrow and comparatively deep cracks at the surface of highly thermo-mechanically loaded parts made of 12% Ni hot-working maraging tool steel. Laser-remelting of maraging steel is, due to very good weldability and flexibility of the process, very prospective for repair of fatigued surfaces of parts made of this steel at which the presence of surface microcracks may be observed. In addition to the efficiency of crack remelting, the influence of laser-remelting on the heat-affected zone in terms of its microstructure and residual stresses was also studied. The microstructure in the laser-remelted track is cellular/dendritic. In the heat-affected zone surrounding the laser-remelted track, the microstructure varies considerably. A microstructure analysis revealed, in the heat-affected zone, five microstructural zones and sub-zones. Residual stresses measured after laser-remelting are with reference to gradual through-depth changing of the stresses favourable.