Restoration of Working Surfaces for Forming Elements from Molds for High-Pressure Casting of Non-Ferrous Metals by Laser Surfacing

The article presents a study of the possibilities for restoring the working surfaces of molds for high-pressure casting of non-ferrous metals by laser surfacing using a filler material. Test specimens with parameters of real forming elements were manufactured. The influence of nitriding on welded layers and basic material was studied in comparison with one without nitriding. The X-ray diffraction method was used to obtain the phase composition of the surface of the samples in areas submitted to nitriding. Scanning electron microscopy (SEM) was used to determine the microstructure of the nitriding layers, welded layers and bulk material. Energy-dispersive X-ray spectrometry (EDX) was applied to investigate the chemical composition in the welded and nitrided zone. Mechanical property means of microhardness measurements were studied. Four zones were identified after nitriding in the weld area. The first zone closest to the surface with a thickness of 0.025 mm is characterized by a higher microhardness, which reaches 700 HV. The second zone, which is part of the diffusion zone, is 0.1 mm thick, and it is characterized by the same size grains with a similar shape and microhardness, which reaches 600 HV. The microhardness measured in the welded zone after nitriding is 50% greater than that without nitriding. The thickness of the diffusion zone in 1.2343 steel reaches about 0.15 mm, and the microhardness is about 900 HV near the edge, but quickly decreases to 400 HV.