レーザ急冷凝固処理部における棒状共晶凝固組織の生成機構

ステンレス鋼のレーザ表面改質に関する研究(第2報)

抄録

Three kinds of Fe-Cr-Ni ternary alloys were surface-melted by a CO₂ laser and effects of rapid solidification on solidification modes and microstructures were investigated. It was found that characteristic rod-like eutectic structure formed in these alloys rapidly solidified by laser surface melting which could not be seen in conventional TIG weld metals. The rod-like eutectic structure almost formed in the limited compositional range with iron content of more than 57% in which primary ferrite solidification occurred in conventional TIG weld metals. It was also seen that the formation tendency of the rod-like eutectic structure first increased and then decreased with increasing laser traveling velocity. Austenite in the rod-like eutectic structure was a rod-like in shape and orientation relationship of ‹100› δ// ‹100› γ was confirmed between austenite and ferrite. STEM analysis revealed that element distributuin across austenite and ferrite was not so largely changed in the rod-like eutectic structure comparing with that in vermicular ferrite structure in the TIG weld metal.