2. Kev Tswj Ib puag ncig: Tshem tawm cov kev cuam tshuam hauv zos
2.1 Iron Contamination thiab Hydrogen Embrittlement Prevention
Iron contamination sawv cev rau ib qho ntawm cov insidious tshaj plaws - thiab tiv thaiv tau - ua rau titanium degradation. Thaum cov khoom hlau embed nyob rau hauv titanium nto thaum lub sij hawm fabrication, tuav, los yog txij nkawm, galvanic ob peb daim ntawv. Nyob rau hauv tej yam pH thiab galvanic corrosion scenarios saum toj no 75℃(165℃F), ob niam txiv no tsav atomic hydrogen mus rau hauv lub titanium matrix, ua nkig hydride theem uas hnyav txo ductility.
Kev tshawb fawb lees paub tias hydrogen nqus tau pib thaum cov hlau / npib tsib xee paug nyob rau ntawm titanium nto. Yog hais tias cov ntsiab lus hydrogen ntau tshaj 500 ppm, cov khoom raug kev txom nyem chipping nyob rau hauv load. Kev tiv thaiv kom tiav yuav tsum tshem tawm cov kab mob hlau los ntawm nitric acid pickling ua ntej scale txias.
Kev Tswj Xyuas Tseem Ceeb:
- Dedicated stainless hlau los yog tooj liab -alloy tooling rau tag nrho cov titanium tuav - carbon steel tiv tauj nruj me ntsis txwv
- Segregated fabrication thaj chaw tiv thaiv tus ntoo khaub lig- paug los ntawm carbon steel sib tsoo plua plav
- Nitric acid passivation (20-40% HNO₃) rau decontamination ua ntej vuam los yog kev kho cua sov
- Tshaj tawm -welding tu nrog cov roj inert trailing shields los tiv thaiv oxidation-induced contamination
Fabrication thiab kho kom huv si tseem ceeb heev kom tsis txhob titanium hydriding. Cov tshuaj tiv thaiv hydriding tuaj yeem txuas ntxiv mus kom txog thaum ua tiav qhov kev poob qis, thiab txhua qhov kev ntxhov siab tsis ntev los no tuaj yeem cuam tshuam cov khoom cuam tshuam -txawm yog los ntawm kev ntxhov siab lossis thaum lub sijhawm tu.
2.2 Crevice Corrosion Management hauv Chloride Service
Crevice corrosion tshwm sim nyob rau hauv nruj nreem nyob rau hauv cov qauv tsim-flange kev twb kev txuas, gasket nto, raj - mus rau -tubesheet expansions, thiab bolted pob qij txha- los yog hauv qab scale deposits npog titanium nto. Thaum cov kev tshawb fawb thaum ntxov tau qhia tias titanium tiv thaiv crevice corrosion nyob rau hauv dej hiav txwv, tom qab kev tshawb fawb tau lees paub tias siab -kub chloride media (xws li seawater heat exchangers) thiab ntub chlorine gas ib puag ncig tuaj yeem ua rau muaj kev tawm tsam.
Crevice corrosion susceptibility nyob rau hauv titanium ua raws li qhov kev txiav txim Cl⁻ > Br⁻ > I⁻- chloride ib puag ncig ua rau muaj kev pheej hmoo siab tshaj plaws, cuam tshuam rau titanium pitting corrosion cwj pwm. Tsis tas li ntawd, crevices tsim ntawm titanium thiab tsis yog -cov ntaub ntawv hlau (PTFE, asbestos) pom muaj kev cuam tshuam ntau dua li titanium-rau-titanium interfaces. Thaum lub sij hawm incubation, oxygen depletion nyob rau hauv lub crevice hloov cathodic cov tshuaj tiv thaiv sab nraud thaum anodic dissolution mus rau sab hauv; chloride ions nkag mus rau sab hauv kom tswj tau qhov sib npaug, thiab titanium ion hydrolysis txo qis pH-tej zaum yuav poob qis dua 1-accelerating passive zaj duab xis tawg.
Mitigation Protocol:
- PTFE-lined lossis tsis yog-cov khoom siv hlau sib xyaw ua kom ruaj khov rau hauv cheeb tsam electrochemical ib puag ncig thiab txo qhov kev pheej hmoo corrosion
- Txo flange lub ntsej muag sib txawv los ntawm precision machining (nto roughness Ra tsawg dua los yog sib npaug rau 3.2 μm)
- Rau kev khiav hauj lwm kub siab tshaj 60℃nyob rau hauv chloride-kev pab cuam, qhia TA10 (Ti-0.3Mo-0.8Ni) los txhim kho crevice corrosion kuj
- Kev tshem tawm ib ntus thiab tshuaj xyuas lub ntsej muag sealing thaum lub sijhawm teem sijhawm hloov pauv - tshem tawm TiO₂ cov deposits dawb uas qhia tau hais tias muaj kev tawm tsam crevice
3. Surface Engineering: Hardness Enhancement thiab Wear Mitigation
Titanium qhov tsis tshua muaj qhov tawv tawv (kwv yees li 250-350 HV rau cov khoom lag luam ntshiab) txwv nws qhov kev ua tau zoo hauv kev hnav, fretting, thiab zawv zawg sib cuag. Cov thev naus laus zis hloov kho deg daws qhov kev txwv no yam tsis muaj kev cuam tshuam cov khoom siv hluav taws xob substrate.
3.1 Plasma Nitriding rau Hnav Resistance
Plasma nitriding ua rau tawv tawv TiN thiab Ti₂N cov txheej txheem sib xyaw ntawm titanium nto, txhim kho kev hnav tsis kam. Rau TA7 titanium alloy plasma nitrided ntawm 800℃rau 10 teev, cov nitrided txheej thickness nce mus txog kwv yees li 5 μm, nrog rau deg hardness ncav cuag 1183.6 HV0.05-2.6 npaug tshaj unnitrided substrate hardness. Qhov tseem ceeb tshaj, qhov hnav tus nqi txo qis dua 99.3% piv rau cov khoom tsis kho.
Tsawg-kub arc plasma nitriding ntawm 500℃nrog 400 V bias voltage thiab 1.5 Pa ua haujlwm siab ua rau tuab TiN thiab Ti₂N txheej. Qhov zoo tshaj plaws hnav tsis kam tshwm sim ntawm nitrogen-hydrogen piv ntawm 2: 1 hauv cov txheej txheem roj sib tov. Cov thev naus laus zis no txhim kho TC4 (Ti-6Al-4V) saum npoo av yam tsis muaj kev hloov kho matrix microstructure lossis tag nrho cov yam ntxwv ntawm cov tshuab-txuas ntxiv kev txwv kev ua haujlwm nyab xeeb rau kev siv aerospace thiab marine engineering.
3.2 Anodic Oxidation rau Corrosion Barrier Restoration
Anodizing tsim cov tshuaj tiv thaiv TiO₂ zaj duab xis rau ntawm titanium nto, nrog thickness precisely tswj los ntawm siv DC voltage-feem ntau 10 mus rau 100 volts. Cov txheej oxide loj hlob ncaj qha los ntawm lub hauv paus hlau los ntawm atomic- qib kev sib txuas, tshem tawm cov kev pheej hmoo delamination cuam tshuam nrog cov txheej txheem siv. Zaj duab xis thickness txiav txim siab cov yam ntxwv cuam tshuam xim:
| Qhov voltage (V) | Xim | Kwv yees Oxide Thickness |
| 15 | Bronze | 30 - 50 nm |
| 25 | Ntshav | 50 - 70 nm |
| 40 | Xiav | 70 - 90 nm |
| 70 | Kub | 100 - 120 nm |
| 90 | Paj yeeb/Magenta | 120 - 150 nm |
Anodizing pab ob qho tib si zoo nkauj thiab ua haujlwm. Rau cov kev siv tu, anodic oxidation regenerates passive zaj duab xis ntawm titanium nto uas qhia discoloration los yog thaum ntxov - theem corrosion. Cov txheej txheem restores tag nrho corrosion kuj tsis tas yuav tsum tau hloov cov khoom. TiO₂ zaj duab xis hardness ranges ntawm HV 300-500-qis dua li nitrided nto tab sis txaus rau cov kev pab cuam tshuaj lom neeg uas muaj abrasive tsawg tsawg.
Txuas ntxiv...
