麻時效鋼氫環境中缺口拉伸特性

Laser Surface Annealing of T-250 Maraging Steel

本研究是針對T-250麻時效鋼，經不同時效處理與雷射退火處理試件，於各種環境中，進行缺口拉伸試驗，由實驗結果顯示：482℃時效試件於大氣環境中，呈現最大之缺口強度，而固溶處理試件，則有最低之缺口強度。氣態氫環境中，除482℃時效處理試件缺口強度顯著劣化外，其餘試件均可避免外界氫氣氛的嚴重損害，且482℃時效試件，在氣態氫環境中會因缺口效應而造成破壞模轉變，由原先Quasi-cleavage破壞轉變成沿品破壞模式。在飽和硫化環境中，所有試件缺口強度均明顯下降，其破壞面均呈現沿品破壞特徵。593℃過時效試件顯示最高缺口強度及較低之強度損失率，而482℃時效試件氫脆化嚴重，缺口強度劣化最顯著。雷射表面退火處理，有助於降低482℃時效試件在氣態氫環境中之氫脆性，但雷射處理試件在硫化氫環境中亦顯著劣化。

The notched tensile strength (NTS) of T-250 maraging steel aged at various conditions and laser-annealed specimen was determined. In air, the 482℃/4hr aged specimen had the highest NTS among the specimens. Obvious degradation in NTS was found for the 482℃ aged specimen tested in gaseous hydrogen, while other specimens were resistant to gaseous hydrogen embrittlement. This reduction in NTS was also related to the change of fracture features from ductile fracture in air to mixed mode fracture in H2. Severe decrease in NTS was found for all the specimens tested in the saturated H2S solution, which associated with intergranular fracture. Gaseous hydrogen embrittlement susceptibility of 482℃ aged specimen can be reduced by subjecting to laser-annealing treatment.