Qhov Volume Fraction ntawm Alpha-Phase hauv Dual-Phase Titanium Alloy Heater Tube Hloov Cov Hydrogen Diffusion Coefficient Li Cas thiab Qhov Kev Nyuaj Siab rau Kev ncua Hydride Cracking?
Tso lus
Hydrogen diffusion cwj pwm hauv dual-theem titanium alloys (piv txwv li Qib 5, Ti-6Al-}4V) yog tswj los ntawm qhov ntim feem ntawm alpha-theem (HCP) thiab beta-phase (BCC). Hauv theem beta (BCC qauv), hydrogen diffuses sai dua nyob rau theem alpha. Qhov ntim ntau dua ntawm alpha-theem sib raug rau qis dua hydrogen diffusion coefficient thiab ntau dua qhov kev ntxhov siab ntawm ncua sij hawm hydride cracking (DHC). Rau qib 5 alloy (nyob ib ncig ntawm 50 txog 60 feem pua alpha), qhov sib txawv ntawm qhov sib txawv yog qhov nruab nrab thiab qhov kev ntxhov siab rau DHC yog 150 txog 200 megapascals.
DHC Resistance vs. Quantitative Alpha-Phase Fraction
Alpha-Phase Volume Fraction (%) Alloy Piv txwv H Diffusion Coefficient (cm2/s, 25 degree) DHC Threshold Stress (MPa) 100 Qib 2 (kev lag luam ntshiab) 2 × 10-10 120–180 70 Qib 9 (Ti{{22}5}3Al-2. 10-10 160–220 50–60 Qib 5 (Ti-6Al-4V) 8 × 10-10 180–250 30–40 Beta-C (Ti-35V-15Cr) 2 × 10-9 200–280 0 Beta-21S (Ti-15Nb-3} × 3}
Kev cuam tshuam ntawm Alpha-Phase Fraction ntawm Hydrogen Tolerance
Alpha feem (%)|Max tso cai H rau<0.1 mm/year Crack Growth (ppm) | Recommended for Sour Service 100 | 150-200 |Marginal 70 200-300 Acceptable
50–60 300–{2}} GoodVery Good 0 600-1,000 Zoo heev
Tswv yim Engineering
Increasing DHC threshold stress for hydrogen-rich sour service (H2S partial pressure >0.1 bar) Qhia meej dual theem alloys nrog qis dua alpha theem ntim feem (piv txwv li Qib 5 lossis Beta-C). Tus kws tshaj lij txhim kho cov hydrogen kam rau ua los ntawm kev kho qhov alpha-feem feem pua.
