Comparison of Measured and Calculated Thicknesses of Martensite anc Ledeburite Shells Around Graphite Nodules in the Hardened Layer aftei Laser Surface Remelting

摘要

The application of laser surface remelting to nodular iron 400-12 causes the material to undergo microstructural changes. The process of rapid heating above the melting-point temperature and the temperature of the austenitic transformation creates conditions for the formation of metastable microstructures, which are the carriers of important technological properties such as high hardness, good wear and corrosion resistance. A newly created austenite cementite microstructure with the presence of graphite nodules in the remelted layer and a martensite ferrite microstructure with graphite nodules in the hardened layer have been observed. Microscopy of the hardened layer was used to analyze the occurrence of martensite or ledeburite shells around the graphite nodules in ferrite matrix. The size of the shells was later estimated by diffusion calculations. The qualitative effects of the changed microstructures were additionally verified by microhardness measurements in the modified layer and microhardness measurements of characteristic microstructures around the graphite nodules in the hardened layer.