| TC4has become one of essential metal materials of new technology and newequipment with its widely used in aerospace, ship and ocean, energy and chemical and vehicleindustry. The surface of TC4can form high hardness coating with surface treatment of C andB, so the wear resistance is improved.The surface treatment with C, B and B4C under the condition of vacuum was adopted inthis paper. Then the microstructure, the composition and distribution of hard phase and thehardness variation law of the TC4coating under different treatment technology were studied,the strengthening micromechanism of the coating and the formation mechanism of hard phasewere analyzed on the basis of EET theory.It is shown that the surface hardness is the highest at900℃×10h and TiC is formedwith C treatment. The surface hardness is the highest at1000℃×20h, TiB2and TiB areformed with B treatment, the amount of TiB is more than that of TiB2. The surface hardnessis the highest at1000℃×20h, TiC, TiB2and TiB are formed with B4C treatment, the amountof TiB is the most, that of TiB2is second and that of TiC is the least.After the surface treatment with C, B and B4C, the coating hardness of the sample crosssection is obviously descended with the increasing of the distance from the surface, at thesame time, the hardness gradient is continuous decreased.It is found that the surface hardness and wear resistance are increased after the surfacetreatment, their micro-mechanism lie in the banding force of the strongest covalent bond ofTiC, TiB and TiB2far greater than that of the matrix.The calculation results of valence electron structure show that the formation of TiB iseasier, the formation of TiC is more difficult than that of TiB while TiB2is the most difficultto form. This result is consistence to the judging result of Gibbs free energy calculation andthe experiment result. The stability of TiC is close to that of TiB while the stability of TiB2isfar greater than that of TiC and TiB. |
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