ペースト法によるTi及びTi合金のホウ化処理

概要

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Paste-bonding of titanium and Ti- 6 Al- 4V alloy was carried out in the air by using mixtures made up of B4C and Na2B4O7 as the main constituents, NaBF4, NH4Cl and NaCl as the activators and Ca (OH)2 as binder. The influence of paste compositions on boride formation, and the structure, hardness and wear behavior of the boride layers formed onto the metals were investigated. The results obtained are summarized as follows: The most suitable composition of bonding paste for titanium was 65%B4C, 20%Na2B4O7, 8.5%NaBF4, 2.5% (NH4Cl+NaCl) and 4%Ca (OH)2, and that for Ti- 6 Al- 4V was 75%B4C and 10%Na2B4O7, with the other materials in the same proportions as for titanium. Two phases of titanium boride were formed TiB2 on the surface and TiB inside. The TiB2 surface had a hardness of HK (0.196N) 3200-4500. Under identical conditions of formation, the boride layer formed on the titanium was slightly thicker than that on the Ti- 6 Al- 4V alloy, but when the surface roughness of after bonding is taken into account, the Ti- 6 Al- 4V alloy is superior to the titanium as a candidate for bonding. The wear behavior of paste-bonded titanium and Ti- 6 Al- 4V alloy was greatly improved over that of untreated specimens.
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