本研究探討熱處理對 17-4 PH 不銹鋼氫誘發破裂行為之影響。藉由熱處理其微觀組織與機械強度，於添加1g/L 硫氰化銨的0.5 M 硫酸水溶液中進行陰極定電位充氫試驗，觀察氫誘發破裂行為與其氫固溶量差異。此外，利用熱脫附光譜（TDS）試驗與彈簧拉伸試驗解析氫於材料內之捕捉型態及氫脆化影響。
17-4 PH 不銹鋼透過不同熱處理條件使含銅析出相析出達強度調整，以480 ℃/1h 時效處理擁有最高微硬度與抗拉強度；經580 ℃/1h 時效處理，則因析出物聚集且粗化，使其強度下降。經陰極充氫後原材與經480 ℃ 時效處理試片擁有較高之氫誘發破裂敏感度；至於經過固溶處理或者過時效處理（580 ℃）的17-4 PH 不銹鋼，其氫誘發破裂敏感性則較低。觀察氫誘發裂紋，其起始位置好發於容易捕捉及聚集氫原子的先前沃斯田體晶界、板條狀麻田散體晶界與介在物周圍。熱脫附光譜（thermaldesorption spectroscopy, TDS）分析結果顯示，原材與經480 ℃ 時效處理具有較低的氫原子束縛能，氫原子容易於材料晶格間擴散、聚集在缺陷及應力集中處，提升氫誘發破裂敏感性。而經580 ℃ 時效處理可改變析出物與基地組織兩相介面的結構，提升材料的氫捕捉能力，同時提升總體氫含量；但是氫原子於材料內部晶格間的固溶量則降低，因此氫誘發破裂敏感性降低。彈簧拉伸試驗結果表明，不論何種熱處理，一旦氫滲入17-4 PH 不銹鋼中，皆造成最大抗拉強度、斷面減縮率與伸長量下降。無論是氫誘發破裂或是氫脆之破斷面，皆顯示脆性的沿晶、穿晶、劈裂特徵形貌，換言之，當氫被吸收、固溶於17-4 PH 不銹鋼中，其破裂面形貌由延性轉為脆性特徵。

The microstructure and mechanical properties of 17-4 precipitation hardening (PH) stainless steel (SS) can be modified by heat treatment associated with the precipitation of copper-rich particles in the matrix. Tempering at 480 ℃ for 1h resulted in an increase in hardness and tensile strength but at the expense of high susceptibility to hydrogen induced cracking (HIC). Hydrogen is likely to be absorbed and trapped in interstitial lattice sites, dislocation cores, grain boundaries and incoherent interfaces (commonly associated with inclusions), etc., which can possibly act as initiation sites for HIC but with different propensity. The results of thermal desorption spectroscopy (TDS) analysis showed that hydrogen trapping energy is relatively low after 480 ℃/1h aging treatment, revealing the diffusible nature of absorbed hydrogen. However, the higher susceptibility to HIC could probably attributed to the higher hydrogen content in the dislocation cores or interstitial lattice sites. Aging treatment at 580 ℃/1h caused an increase of the formation of incoherent interfaces, which normally became the irreversible hydrogen trapping sites. As a result, the lattice hydrogen concentration was lowered and a decrease in HIC susceptibility was observed. Spring load tensile testing results indicated that 17-4 PH SS became embrittled by revealing the transition from ductile to brittle fracture if it was cathodically charged with hydrogen, regardless of thermal treatment.

[1] S. S. M. Tavares, J. M. Pardal, L. Menezes, C. A. B. Menezes and C. D’Ávila, "Failure analysis of PSV springs of 17-4PH stainless steel," Engineering Failure Analysis, vol. 16, no. 5, pp. 1757-1764, 2009.
[2] C. F. Arisoy, G. Başman and M. K. Şeşen, "Failure of a 17-4 PH stainless steel sailboat propeller shaft," Engineering Failure Analysis, vol. 10, no. 6, pp. 711-717, 2003.
[3] ASTM International. ASTM A693-16 Standard Specification for Precipitation-Hardening Stainless and Heat-Resisting Steel Plate, Sheet, and Strip. West Conshohocken, PA; ASTM International, 2016.
[4] D. A. Porter, K. E. Easterling, and M. Sherif, "Diffusionless transformations," in Phase Transformations in Metals and Alloys, third edition. Boca Raton, CRC press, 2009
[5] G. Krauss, "Martensite in steel: strength and structure," Materials Science and Engineering: A, vol. 273, pp. 40-57, 1999.
[6] H. Kitahara, R. Ueji, N. Tsuji, and Y. Minamino, "Crystallographic features of lath martensite in low-carbon steel," Acta Materialia, vol. 54, no. 5, pp. 1279-1288, 2006.
[7] U. K. Viswanathan, S. Banerjee, and R. Krishnan, "Effects of aging on the microstructure of 17-4 PH stainless steel," Materials Science and Engineering: A, vol. 104, pp. 181-189, 1988.
[8] K. C. Antony, "Aging Reactions in Precipitation Hardenable Stainless Steel," The Journal of The Minerals, Metals & Materials Society, vol. 15, no. 12, pp. 922-927, 1963.
[9] H. J. Rack and D. Kalish, "The strength, fracture toughness, and low cycle fatigue behavior of 17-4 PH stainless steel," Metallurgical Transactions, journal article vol. 5, no. 7, pp. 1595-1605, 1974.
[10] K. R. Hayes, "Hydrogen Embrittlement in 17-4PH Stainless Steel," Naval Weapons Center, China Lake, CA, 1982.
[11] T. Velikanova and M. Turchanin, MSIT, " Chromium–Copper–Iron," in Ternary Alloy Systems: Phase Diagrams; Crystallographic and Thermodynamic Data, vol 11D3, Berlin, Heidelberg, Springer, 2008 pp. 88-128.
[12] M. Murayama, K. Hono, and Y. Katayama, "Microstructural evolution in a 17-4 PH stainless steel after aging at 400 °C," Metallurgical and Materials Transactions A, journal article vol. 30, no. 2, pp. 345-353, 1999.
[13] S. Mahadevan, R. Manojkumar, T. Jayakumar, C. R. Das, and B. P. C. Rao, "Precipitation-Induced Changes in Microstrain and Its Relation with Hardness and Tempering Parameter in 17-4 PH Stainless Steel," Metallurgical and Materials Transactions A, vol. 47, no. 6, pp. 3109-3118, 2016.
[14] C. Hsiao, C. Chiou, and J. Yang, "Aging reactions in a 17-4 PH stainless steel," Materials Chemistry and Physics, vol. 74, no. 2, pp. 134-142, 2002.
[15] G. Yeli, M. A. Auger, K. Wilford, G. D. W. Smith, P. A. J. Bagot, and M. P. Moody, "Sequential nucleation of phases in a 17-4PH steel: Microstructural characterisation and mechanical properties," Acta Materialia, vol. 125, pp. 38-49, 2017.
[16] Z. Wang, X. Fang, H. Li, and W. Liu, "Atom Probe Tomographic Characterization of Nanoscale Cu-Rich Precipitates in 17-4 Precipitate Hardened Stainless Steel Tempered at Different Temperatures," Microscopy and Microanalysis, vol. 23, no. 2, pp. 340-349, 2017.
[17] R. McCright, "Effects of environmental species and metallurgical structure on the hydrogen entry into steel," in Stress Corrosion Cracking and Hydrogen Embrittlement of Iron Base Alloys, vol. 5: NACE, 1973, pp. 306-325.
[18] J. Bockris and R. Thacker, "Technical Report No. 3," ONR Contract NONR, vol. 551, no. 22, pp. 36-028.
[19] J. O. M. Bockris, B. E. Conway, E. Yeager, and R. E. White, "Comprehensive treatise of electrochemistry," 1980.
[20] M. Smialowski, Hydrogen in steel: effect of hydrogen on iron and steel during production, fabrication, and use, Elsevier, 2014.
[21] S. Lynch, "Hydrogen embrittlement (HE) phenomena and mechanisms," in Stress Corrosion Cracking: Elsevier, 2011, pp. 90-130.
[22] A. Pundt and R. Kirchheim, "Hydrogen in metals: microstructural aspects," Annual Review of Materials Research, vol. 36, pp. 555-608, 2006.
[23] G. Pressouyre, "A classification of hydrogen traps in steel," Metallurgical Transactions A, vol. 10, no. 10, pp. 1571-1573, 1979.
[24] J. P. Hirth, "Effects of hydrogen on the properties of iron and steel," Metallurgical Transactions A, vol. 11, no. 6, pp. 861-890, 1980.
[25] B. A. Szost, R. H. Vegter, and P. E. J. Rivera-Díaz-del-Castillo, "Hydrogen-Trapping Mechanisms in Nanostructured Steels," Metallurgical and Materials Transactions A, journal article vol. 44, no. 10, pp. 4542-4550, 2013.
[26] R. P. Gangloff, "Hydrogen assisted cracking of high strength alloys," Aluminum Co of America, Alcoa Technical Center, New Kensington, PA, 2003.
[27] D. Pérez Escobar, C. Miñambres, L. Duprez, K. Verbeken, and M. Verhaege, "Internal and surface damage of multiphase steels and pure iron after electrochemical hydrogen charging," Corrosion Science, vol. 53, no. 10, pp. 3166-3176, 2011.
[28] M. H. N. Edition, Volume 13 Corrosion," Evaluation of Galvanic Corrosion”, ed. JE Davis, ASM International, p. 235, 1987.
[29] C. Zapffe and C. Sims, "Hydrogen embrittlement, internal stress and defects in steel," Transactions of the Metallurgical Society of AIME, vol. 145, no. 1941, pp. 225-271, 1941.
[30] L. B. Pfeil, "The effect of occluded hydrogen on the tensile strength of iron," Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, vol. 112, no. 760, pp. 182-195, 1926.
[31] A. R. Troiano, "The role of hydrogen and other interstitials in the mechanical behavior of metals," Transactions of American Society for Metals, vol. 52, pp. 54-80, 1960.
[32] R. Oriani, "Whitney award lecture—1987: hydrogen—the versatile embrittler," Corrosion, vol. 43, no. 7, pp. 390-397, 1987.
[33] N. Petch and P. Stables, "Delayed fracture of metals under static load," Nature, vol. 169, no. 4307, p. 842, 1952.
[34] C. Beachem, "A new model for hydrogen-assisted cracking (hydrogen “embrittlement”)," Metallurgical and Materials Transactions B, vol. 3, no. 2, pp. 441-455, 1972.
[35] I. Robertson, "The effect of hydrogen on dislocation dynamics," Engineering Fracture Mechanics, vol. 64, no. 5, pp. 649-673, 1999.
[36] W. Y. Choo and J. Y. Lee, "Thermal analysis of trapped hydrogen in pure iron," Metallurgical Transactions A, journal article vol. 13, no. 1, pp. 135-140, 1982.
[37] H. E. Kissinger, "Reaction kinetics in differential thermal analysis," Analytical chemistry, vol. 29, no. 11, pp. 1702-1706, 1957.
[38] R. Silverstein and D. Eliezer, "Mechanisms of hydrogen trapping in austenitic, duplex, and super martensitic stainless steels," Journal of Alloys and Compounds, vol. 720, pp. 451-459, 2017.
[39] M. Koyama, H. Springer, S. V. Merzlikin, K. Tsuzaki, E. Akiyama, and D. Raabe, "Hydrogen embrittlement associated with strain localization in a precipitation-hardened Fe–Mn–Al–C light weight austenitic steel," international journal of hydrogen energy, vol. 39, no. 9, pp. 4634-4646, 2014.
[40] H. Dogan, D. Li, and J. R. Scully, "Controlling Hydrogen Embrittlement in Precharged Ultrahigh-Strength Steels," CORROSION, vol. 63, no. 7, pp. 689-703, 2007.
[41] S. Yamasaki, M. Kubota, and T. Tarui, "Evaluation method for delayed fracture susceptibility of steels and development of high tensile strength steels with high delayed fracture resistance," Nippon Steel Technical Report(Japan), vol. 80, pp. 50-55, 1999.
[42] G. Pressouyre, J. Fidelle, and R. Arnould-Laurent, "Trap theory of hydrogen embrittlement: experimental investigations," Hydrogen Effects in Metals, pp. 27-36, 1980.
[43] J. R. Davis, Stainless steels, pp. 197-201, ASM international, 1994.
[44] I. O. Shim and J. G. Byrne, "A study of hydrogen embrittlement in 4340 steel I: Mechanical aspects," Materials Science and Engineering: A, vol. 123, no. 2, pp. 169-180, 1990.
[45] A. F. Liu, Mechanics and mechanisms of fracture: an introduction. ASM International, 2005.
[46] T. L. Anderson, Fracture mechanics: fundamentals and applications. CRC press, 2017.
[47] A. Nagao, C. D. Smith, M. Dadfarnia, P. Sofronis, and I. M. Robertson, "The role of hydrogen in hydrogen embrittlement fracture of lath martensitic steel," Acta Materialia, vol. 60, no. 13-14, pp. 5182-5189, 2012.
[48] A. Shibata, Y. Momotani, T. Murata, T. Matsuoka, M. Tsuboi, and N. Tsuji, "Microstructural and crystallographic features of hydrogen-related fracture in lath martensitic steels," Materials Science and Technology, vol. 33, no. 13, pp. 1524-1532, 2017.
[49] A. Shibata, T. Murata, H. Takahashi, T. Matsuoka, and N. Tsuji, "Characterization of Hydrogen-Related Fracture Behavior in As-Quenched Low-Carbon Martensitic Steel and Tempered Medium-Carbon Martensitic Steel," Metallurgical and Materials Transactions A, journal article vol. 46, no. 12, pp. 5685-5696, 2015.
[50] S. Frappart, A. Oudriss, X. Feaugas, J. Creus, J. Bouhattate, F. Thébault, L. Delattre and H. Marchebois, "Hydrogen trapping in martensitic steel investigated using electrochemical permeation and thermal desorption spectroscopy," Scripta Materialia, vol. 65, no. 10, pp. 859-862, 2011.
[51] F. G. Wei and K. Tsuzaki, "Response of hydrogen trapping capability to microstructural change in tempered Fe–0.2C martensite," Scripta Materialia, vol. 52, no. 6, pp. 467-472, 2005.