| In order to improve wear-resistance of carbon tool steel, a study of TiC-surface alloying was carried out by irradiation of CO₂laser. Mixtures of TiC and Co powders were applied directly on specimens by coating powder slurry suspended in alchohol to the thickness of 70㎛. Surface alloyed layers were obtained by single and overlapping laser tracks. Microstructural observation, X-ray diffraction analysis, microhardness test and wear test were carried out on earth specimen. Strengthening mechanisms of TiC-surface alloyed hayer were martensitic transformation, dispersion of TiC particles and grain refinements in alloyed layer. Although the alloyed layer was martensitic structure, lots of undissolved Fe₃C were present due to rapid heating and cooling. Mixtures of TiC+ 5% Co resulted in an increase of hardness by elevating Ms temperature, but further increase of Co reduced the hardness by stabilization of austenite. Even if Fe₃C was decarburized in TiC-surface alloyed layer when it was annealed at high temperature, TiC was not decarburized. Thus a little higher wear-resistance and heat-resistance are expected compared with carbon tool steel when it is used in high temperature. |
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