Thaum twg Oxidation Resistance ntawm Ntshiab Titanium Txo?
Qhov kub siab tshaj qhov ntsuas qhov tseem ceeb
Pure titanium exhibits good oxidation resistance at temperatures below 400℃, as the surface TiO₂ film remains dense and adherent, effectively blocking further oxygen infiltration. Txawm li cas los xij, thaum qhov kub siab tshaj 400 degree, oxidation tus cwj pwm ntawm ntshiab titanium hloov pauv loj heev:
Ntawm 400-600 degree: TiO₂ zaj duab xis pib loj hlob sai nyob rau hauv tuab, thiab nws cov qauv hloov los ntawm ib tug tuab, tiv thaiv rutile theem mus rau ib tug ntau ntxeem tau anatase los yog brookite theem nyob rau hauv cov cheeb tsam. Meanwhile, me me ntawm interstitial oxygen atoms diffuse mus rau hauv titanium matrix, ua ib tug brittle oxygen-enriched txheej nyob rau hauv lub oxide zaj duab xis, uas ua rau cov hlau tsis muaj zog structural kev ruaj ntseg thaum txo cov zaj duab xis barrier nyhuv.
Tshaj 600 degree: Cov txheej txheem oxidation nkag mus rau "parabolic{0}} mus rau -linear" theem hloov. TiO₂ zaj duab xis poob nws cov khoom tiv thaiv tag nrho vim qhov tawg loj thiab tawg los ntawm kev ntxhov siab thermal (tshwm sim los ntawm kev tsis sib haum xeeb hauv thermal expansion coefficients ntawm oxide zaj duab xis thiab titanium substrate). Cov pa oxygen nkag mus rau hauv matrix ntawm tus nqi nrawm, thiab tsim kom tsawg - adhesion oxide txheej (xws li Ti₂O₃ thiab TiO hauv sub- thaj tsam saum npoo) ua rau muaj kev puas tsuaj oxidation ntawm ntshiab titanium, nrog rau oxidation tus nqi nce exponentially nrog kub.
High - qhov kub thiab txias ib puag ncig nrog cov roj corrosive tshwj xeeb
Txawm hais tias qhov kub thiab txias nyob hauv qhov nominal "kev nyab xeeb" (qis dua 400 degree), muaj qee yam corrosive gas impurities yuav degrade ntshiab titanium oxidation tsis kam:
chlorine-muaj roj (xws li Cl₂, HCl vapor): Cov chloride ions tuaj yeem nkag mus rau TiO₂ zaj duab xis los ntawm microcracks lossis cov ciam teb, ua rau cov titanium los ua cov titanium chlorides tsis haum (xws li, TiCl₄). Qhov no "tiv thaiv corrosion" mechanism rhuav tshem qhov txuas ntxiv ntawm cov yeeb yaj kiab tsis tu ncua thiab tiv thaiv nws tus kheej - kho, ua rau thaj chaw pitting lossis corrosion tsis sib xws txawm nyob rau nruab nrab kub.
Sulfur{0}}muaj cov pa roj (xws li SO₂, H₂S): Thaum kub siab tshaj 300 degree, sulfur atoms tuaj yeem xa mus rau hauv titanium matrix, tsim cov titanium sulfides nkig (xws li TiS, TiS₂) ntawm cov ciam teb. Cov sulfides no tsis tsuas yog txo cov hlau ductility tab sis kuj cuam tshuam kev ncaj ncees ntawm TiO₂ zaj duab xis, ua rau nws muaj kev cuam tshuam rau oxygen nres thiab ua kom oxidation.
Nitrogen{0}}nplua nuj huab cua ntawm qhov kub thiab txias: Tshaj 500 degree, nitrogen reacts nrog titanium los ua ib qho nyuaj thiab nkig titanium nitride (TiN) rau saum npoo thiab hauv matrix. Thaum TiN muaj qee qhov kev tiv thaiv oxidation, nws tsim ua rau muaj kev ntxhov siab sab hauv hauv oxide zaj duab xis, ua rau tawg thiab tsim cov channel rau oxygen kom nkag mus rau hauv cov hlau hauv qab.
Cyclic thermal loading tej yam kev mob
Rov ua cua sov thiab cua txias (piv txwv li, hauv cov chaw ua khoom siv hluav taws xob lossis lub tshuab hluav taws xob aerospace uas tau pib ntau zaus- nres kev ua haujlwm) ua rau muaj kev cuam tshuam loj heev rau cov titanium oxidation tsis kam:
Thermal expansion thiab contraction ntawm TiO₂ zaj duab xis thiab titanium substrate ua rau cyclic kev nyuaj siab, ua rau cov tsim ntawm microcracks thiab delamination nyob rau hauv lub oxide txheej.
Txhua lub voj voog thermal nthuav tawm cov hlau titanium tshiab rau hauv qhov chaw oxidizing ua ntej zaj duab xis tuaj yeem ua rau nws tus kheej - kho, ua rau muaj kev puas tsuaj oxidation thiab maj mam txo cov yeeb yaj kiab tiv thaiv lub sijhawm.
Muaj cov ntsev molten los yog tsawg - melting - cov kab mob hlau
Hauv ib puag ncig uas muaj cov ntsev ntsev (piv txwv li, NaCl, Na₂SO₄ hauv siab -kub muaj txheej txheem) lossis qis- melting- cov ntsiab lus hlau (xws li, aluminium, magnesium, lead), ntshiab titanium's oxidation kuj tsis zoo:
Molten ntsev tuaj yeem ua tau raws li electrolytes, inducing electrochemical corrosion uas ua rau lub TiO₂ zaj duab xis, thaum tseem ua kom yooj yim tsim cov qis - melting - taw tes titanium tebchaw uas ua rau cov yeeb yaj kiab tsis ua haujlwm.
Tsawg- melting- taw tes hlau tuaj yeem xa mus rau hauv titanium matrix ntawm qhov kub thiab txias, tsim cov eutectic alloys thiab ua rau intergranular embrittlement, uas ua rau cov qauv kev ruaj ntseg ntawm cov hlau tsis muaj zog thiab ua rau cov oxide zaj duab xis ntau dua tuaj yeem tawg thaum oxidation.
