雰囲気制御高周波誘導加熱微粒子ピーニングシステムを用いて, 鋼表面にNi-Al金属間化合物層の創成を試みた。その結果, NiとAl粒子を1 : 4の割合で混練した粒子でAIH-FPPを施すと, Ni-Al金属間化合物層が形成された。これは, 投射粒子に含まれるAlがフラックスとして作用することにより局所的にNiとFeの融点が低下すること, また, NiとAlの燃焼合成反応により, 局所的に温度が上昇したためである。さらに, 高温連続酸化試験の結果, 処理した部位は優れた耐酸化性を持つことがわかった。これは, Ni-Al金属間化合物層が高温酸化雰囲気中でAl2O3を連続的に生成しそれが保護被膜となるためである。
To form a Ni-Al intermetallic compound layer on a carbon steel surface, AIH-FPP was carried out at 900℃ in argon atmosphere with a Ni and Al particle milled by means of planetary ball mills. The treated surface was analyzed using SEM, EDX and an XRD. Oxidation test was carried out at 900℃ for 100 hours. Results showed that the Ni-Al intermetallic compound layer with a thickness of 200 μm was formed in the case of the specimen treated by the aluminum rich shot particles; the ratio of Ni to Al was 1 to 4 at.%. This was because (i) melted Al particles reduced the melting point of Ni particles and Fe substrate, and (ii) partially melted area promoted a combustion synthesis reaction between Ni and Al, resulting in forming the Ni-Al intermetallic compound layer. The AIH-FPP treated surface showed a higher oxidation resistance than that of the un-treated specimen. This was because Al2O3 continually created from the Ni-Al intermetallic compound layer protected the steel substrate.
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