1. Hastelloy B-3 tau tsim los ua ib qho kev txhim kho rau cov khoom siv dav siv B-2. Dab tsi yog qhov tseem ceeb metallurgical tsis muaj zog ntawm B-2 uas B-3 tshwj xeeb hais txog, thiab nws cov chemistry hloov pauv li cas (tshwj xeeb txog Ni, Mo, thiab Cr) muab kev daws teeb meem li cas?
Thawj qhov tsis muaj zog ntawm B-2 yog nws qhov ua rau muaj kev cuam tshuam ntawm cov txheej txheem intermetallic tom qab lub sijhawm ntev ntawm qhov kub thiab txias (600-1100℃F / 316-593 degree), ib qho mob uas tuaj yeem tshwm sim thaum lub caij txias txias tom qab vuam, txo kev ntxhov siab, lossis hauv cov txheej txheem kub kub.
B-2's Teeb meem: Ni-Mo Phase nag lossis daus
Hauv B-2, cov ntsiab lus siab molybdenum (~28%) hauv qis-chromium, qis- hlau matrix yog metastable. Kev ncua sij hawm nyob rau hauv qhov ntsuas kub tseem ceeb ua rau cov nag lossis daus ntawm cov theem intermetallic xws li mu theem (μ-theem - Ni₇Mo₆) thiab P-theem. Cov theem no yog ib qho nyuaj, nkig, thiab, qhov tseem ceeb tshaj plaws, ua rau cov matrix nyob ib puag ncig ntawm molybdenum, tsim cov cheeb tsam hauv cheeb tsam nrog txo qis corrosion kuj. Qhov no tuaj yeem ua rau qhov kev xav tsis zoo ntawm intergranular corrosion thiab embrittlement tom qab vuam lossis hauv kev pabcuam.
B-3's Solution: Chemically Optimized Stability
B-3' s muaj pes tsawg leeg yog qhov tseeb recalibration ntawm Ni-Mo tshuav nyiaj li cas:
Kho Ni/Mo Ratio: Lub molybdenum qis me ntsis (~ 28.5% vs. ~ 28%) thiab npib tsib xee yog nce (~ 65% min) hloov cov hlau sib xyaw kom deb ntawm lub qhov ntswg ntawm lub sijhawm - kub- hloov pauv (TTT) nkhaus rau theem teeb meem tsim.
Tswj Chromium thiab Hlau: Me me tab sis txhob txwm tshaj tawm ntawm Chromium (~ 1.5%) thiab Hlau (~ 1.5%) ntxiv. Cov ntsiab lus no stabilize lub microstructure. Qhov tseem ceeb, lawv muaj kev sib npaug los txhawb kev tsim ntawm ntau benign, blocky M₆C-hom carbides es tsis txhob txuas ntxiv, nplej- ciam teb sib txuas ntawm kev puas tsuaj intermetallic.
Qhov tshwm sim: Cov chemistry no muab qhov tshwj xeeb thermal stability, txuas ntxiv lub sijhawm xav tau rau cov theem teeb meem tsim. Qhov no ua rau cov neeg tsim khoom siv lub qhov rais ua haujlwm loj dua thiab muab cov engineers muaj kev nyab xeeb ntau dua rau hauv -kev pabcuam embrittlement thiab corrosion.
2. Rau hydrochloric acid (HCl) evaporator ua haujlwm ntawm qhov kub thiab txias, B-3 tubing yuav raug teev. Yuav ua li cas nws cov corrosion kuj nyob rau hauv ntshiab, tsis-oxidizing HCl piv rau B-2, thiab dab tsi yog qhov tseem ceeb tswv yim kom zoo dua B-3 muaj thaum lub fabrication thiab vuam ntawm xws li ib chav tsev?
Hauv cov ntshiab, tsis yog -oxidizing hydrochloric acid, corrosion kuj ntawm B-3 thiab B-2 yog qhov tseem ceeb sib npaug thiab zoo heev. Ob lub alloys teeb tsa tus qauv kev lag luam rau cov kev pabcuam no, nrog cov nqi qis heev nyob rau txhua qhov kev xav tau thiab qhov kub thiab txias, suav nrog qhov kub thiab txias.
Qhov Zoo Tshaj Plaws Tseem Ceeb ntawm B-3: Superior Weldability thiab Fabrication Forgiveness.
Qhov zoo ntawm B-3 yog tsis nyob rau hauv nws cov ntshiab acid kev ua tau zoo, tab sis nyob rau hauv nws resilience thaum lub sij hawm tsim khoom:
B-2 Vuam: Yuav tsum muaj kev saib xyuas hnyav. Lub tshav kub- cuam tshuam cheeb tsam (HAZ) ntawm B-2 vuam yog qhov nkag siab zoo rau kev tsim cov molybdenum-depleted aav yog tias txias qeeb dhau. Qhov no yuav tsum muaj kev tswj xyuas nruj ntawm kev sib tshuam ntawm qhov kub thiab txias, feem ntau yuav tsum tau yuam kom txias, thiab txwv tsis pub siv qee yam txheej txheem vuam.
B-3 Vuam: Nws thermally ruaj khov microstructure yog ntau ntau zam txim. Lub HAZ tsis tshua muaj kev cuam tshuam rau kev tsim cov theem teeb meem thiab qhov cuam tshuam ntawm kev tiv thaiv corrosion. Qhov no tso cai rau:
Kev hloov pauv ntau dua hauv cov txheej txheem vuam (xws li cov khoom siv cua sov me ntsis).
Tsawg zog interpass kub tswj.
Qhov kev pheej hmoo txo qis ntawm kev tsim cov khoom siv uas dhau hydrotest tab sis ua tsis tiav ntxov hauv kev pabcuam corrosive vim qhov teeb meem tsis pom kev microstructural hauv thaj tsam weld.
Rau kev tsim cov txheej txheem nyuaj xws li cov evaporator nrog ntau cov welds, B-3 txo qis kev pheej hmoo ntawm kev tsim khoom, txhim kho cov khoom hauv pem teb kom zoo dua qub, thiab xa cov khoom kawg uas muaj kev ntseeg siab dua corrosion-resistant.
3. Txawm hais tias nws cov kev txhim kho, Hastelloy B-3 qhia txog qhov tsis zoo rau tag nrho Ni-Mo alloys. Dab tsi tshwj xeeb ntawm cov kab mob sib kis, txawm tias nyob rau theem kab mob (ppm), tuaj yeem ua rau muaj kev puas tsuaj loj hauv nws cov corrosion hauv kev txo cov kua qaub, thiab dab tsi yog lub luag haujlwm ntawm electrochemical mechanism?
Qhov teeb meem tseem ceeb yog oxidizing cov neeg ua haujlwm. Txawm tias muaj pes tsawg tus (khoom-ib- lab theem) ntawm oxidizing ions- xws li Ferric (Fe³⁺), Cupric (Cu²⁺), Nitrate (NO³⁻), yaj oxygen (O₂), lossis chlorine (Cl₂)- tuaj yeem ua rau muaj kev puas tsuaj loj. kev txiav txim- ntawm- magnitude nce nyob rau hauv corrosion tus nqi.
Electrochemical Mechanism: Cathodic Depolarization
Nyob rau hauv ib tug ntshiab txo acid xws li HCl, tus nqi corrosion ntawm B-3 inherently tsawg vim cathodic cov tshuaj tiv thaiv (hydrogen ion txo: 2H⁺ + 2e⁻ → H₂) kuj qeeb. Qhov no "kinetically txwv" tag nrho cov txheej txheem corrosion.
Thaum oxidizing ion zoo li Fe³⁺ tau qhia, nws muab cov tshuaj tiv thaiv cathodic tshiab, ntau npaum li cas: Fe³⁺ + e⁻ → Fe²⁺.
Cov tshuaj tiv thaiv no yooj yim thiab ua raws li lub zog cathodic depolarizer. Nws siv hluav taws xob sai sai, ua kom nrawm nrawm ntawm cov tshuaj tiv thaiv anodic (hlau tawg: Ni / Mo → ions + electrons).
Cov txiaj ntsig net yog qhov khiav tawm ntawm lub cell. Tus nqi corrosion tsis txwv los ntawm hydrogen evolution tab sis los ntawm diffusion tus nqi ntawm oxidizer rau cov hlau nto, ua rau mob hnyav, nrawm nrawm.
Qhov no yog vim li cas qhov kev qhia tshwj xeeb thiab kev siv B-3 (thiab B-2) xav tau kev tswj xyuas cov txheej txheem kom tsis txhob muaj cov kab mob oxidizing, feem ntau yuav tsum tau siv cov inert purging, high-purity feedstocks, thiab cais tawm los ntawm cov khoom tsis zoo (xws li cov pa roj carbon steel) sab saud.
4. Nyob rau hauv sulfuric acid (H₂SO₄) concentrator cog, cov seem sib txawv tuav cov kua qaub sib txawv. Nyob rau hauv qhov tshwj xeeb concentration / kub tswj yuav B-3 yog qhov kev xaiv zoo tshaj plaws ntawm chromium-muaj alloy xws li Hastelloy C-276, thiab yog vim li cas?
B-3 is the technically optimal choice for hot, concentrated sulfuric acid (>85% H₂SO₄) ntawm qhov kub thiab txias.
Kev Tshawb Fawb ntawm Sulfuric Acid Behavior:
Dilute / Medium Acid (<~85%): Acts as an oxidizing acid, especially when hot or aerated. Resistance in this regime depends on a stable chromium oxide passive film. Alloys like C-276 (Cr ~16%) excel here. B-3, with only ~1.5% Cr, cannot form a stable passive film and would corrode rapidly.
Concentrated Acid (>~ 85%): Coj tus cwj pwm tsis yog -oxidizing, txo cov kua qaub. Nyob rau hauv ib puag ncig no, chromium's passive film tsis ruaj khov. Kev tiv thaiv yog nyob ntawm qhov muaj txiaj ntsig zoo thiab tsis tshua muaj corrosion kinetics ntawm lub hauv paus alloy hauv kev txo cov xov xwm. Qhov no yog lub npe ntawm Ni-Mo alloys. B-3 cov ntsiab lus siab molybdenum muab kev tiv thaiv zoo heev uas chromium-based passivity tsis zoo.
Daim ntawv thov hauv Concentrator:
A concentrator evaporates water from sulfuric acid, increasing its concentration and temperature along the process path. B-3 tubing is ideally suited for the final stages of concentration-the high-temperature, >85% H₂SO₄ ntu (piv txwv li, qhov kawg concentrator, kub hloov kab). Ntawm no, nws yuav ua tau zoo tshaj C-276. C-276 los yog lwm yam Cr-bearing alloys yuav siv nyob rau hauv pem hauv ntej-kawg, qis concentration theem uas lawv passivation muaj peev xwm yog qhov tseem ceeb.
5. Thaum ua qhov kev soj ntsuam tsis ua haujlwm ntawm Hastelloy B-3 raj uas tawg hauv kev pabcuam, ob qho tib si microstructural nta tau pom los ntawm metallography yuav taw tes rau qhov tsis ua haujlwm ntawm "thermally induced embrittlement" es tsis yog "kev ntxhov siab corrosion cracking (SCC) los ntawm oxidizer"?
Qhov sib txawv ntawm cov kev ua tsis tiav no yuav tsum tau tshuaj xyuas txoj kev tawg thiab cov qauv nplej nyob ib puag ncig.
Cov ntaub ntawv pov thawj rau Thermally Induced Embrittlement (los ntawm kev kho cua sov tsis zoo lossis txias txias):
Intergranular Crack Txoj Kev nrog Theem Precipitation: Cracks yuav ua raws li cov ciam teb. Qhov tseem ceeb, kev tshuaj xyuas microscopic (ntawm qhov loj loj, feem ntau nrog etching) yuav nthuav tawm cov kev sib txuas txuas ntxiv ntawm kev nplua, theem nrab theem precipitated raws cov ciam teb. Cov no yog cov intermetallic detrimental (mu theem, P-theem) uas tau tsim, embrittling ciam teb thiab muab ib tug yooj yim txoj kev rau tawg propagation.
Microstructural Pov Thawj ntawm Kev Laus: Cov nplej lawv tus kheej tuaj yeem pom cov cim ntawm dhau- kev laus, xws li kev tsaus ntuj nyob rau hauv lub tshuab ntsuas los ntawm kev nplua, nag lossis daus, paub meej tias lub raj tau raug rau qhov kub thiab txias ntev heev.
Cov ntaub ntawv pov thawj rau Kev Nyuaj Siab Corrosion Cracking (los ntawm cov kab mob oxidizing):
Transgranular lossis Mixed-Mode Cracking: SCC tawg hauv Ni-Mo alloys, thaum feem ntau intergranular, kuj tuaj yeem hloov pauv (txiav los ntawm cov nplej). Txoj kev tsis tshua khi rau cov ciam teb.
Tsis Muaj Cov Phaj Siab Thib Ob: Qhov sib txawv tseem ceeb yog tias cov ciam teb nplej thiab cov matrix nyob ib sab ntawm SCC tawg feem ntau yuav tsis muaj kev sib txuas txuas ntxiv ntawm precipitated intermetallic theem pom hauv thermal embrittlement. Kev tawg yog tsav los ntawm kev tawm tsam electrochemical hauv ib puag ncig tshwj xeeb, tsis yog los ntawm kev lag luam wholesale microstructural degradation los ntawm tshav kub. Kev soj ntsuam ntawm cov khoom siv corrosion ntawm lub ntsej muag tawg (ntawm EDS) kuj tseem tuaj yeem qhia pom muaj cov kab mob oxidizing (xws li hlau, chlorine).
Hauv cov ntsiab lus: Grain ciam teb nrog precipitates=thermal embrittlement. Ntxuav cov ciam teb nrog ib puag ncig tso nyiaj=qhia ntawm SCC.
