Chromium carbide yog cov khoom siv ceramic uas muaj nyob hauv ntau cov tshuaj sib txawv: Cr3 C2, Cr7 C3 thiab Cr23 C6. Nyob rau hauv cov xwm txheej txheem, nws tshwm sim li grey teeb meem. Chromium yog ib qho nyuaj heev thiab corrosion resistant hlau. Nws kuj yog nplaim taws, uas txhais tau hais tias nws tseem muaj zog txawm tias qhov kub thiab txias.
Cov khoom ntawm chromium no ua rau nws muaj txiaj ntsig zoo li cov khoom ntxiv hauv cov hlau alloys. Thaum carbide crystals tau muab tso rau hauv qhov chaw ntawm cov khoom, nws txhim kho hnav tsis kam thiab corrosion kuj thiab tseem khaws cov khoom no ntawm qhov kub thiab txias. Lub complex thiab feem ntau siv compound rau lub hom phiaj no yog Cr3 C2.
Cov ntxhia ntsig txog suav nrog tongbaite thiab isovite (Cr, Fe) 23 C6, ob qho tib si tsawg heev. Lwm cov nplua nuj carbide ntxhia yog yarlongite Cr4 Fe4 NiC4.
Chromium khoom
muajPeb cov qauv siv lead ua sib txawv rau carbide sib haum rau peb cov tshuaj sib txawv:
- Cr23 C6 muaj cov qauv cubic thiab Vickers hardness ntawm 976 kg/mm2.
- Cr7 C3 muaj cov qauv siv lead ua hexagonal thiab microhardness ntawm 1336 kg / mm 2.
- Cr3 C2 yog qhov ruaj khov tshaj plaws ntawm peb qhov sib xyaw thiab muaj cov qauv rhombic nrog microhardness ntawm 2280 kg / mm2.
Vim li no, Cr3 C2 yog lub ntsiab lus ntawm chromium carbide siv hauv kev kho deg.
Synthesis
Carbide bonding tuaj yeem ua tiav los ntawm kev sib tsoo tshuab. Nyob rau hauv cov txheej txheem no, chromium hlau thiab carbon nyob rau hauv daim ntawv ntawm graphite yog pub rau hauv lub pob zeb thiab hauv av rau hauv ib tug zoo hmoov. Tom qab crushing cov khoom, lawv muab tso rau hauv granules thiab raug kub isostatic nias. Qhov kev ua haujlwm no siv cov roj inert, feem ntau argon hauv qhov cub kaw.
Cov khoom siv zog no ua rau lub zog ntawm cov qauv los ntawm txhua sab thaum lub qhov cub sov. Cov cua kub thiab siab ua rau cov graphite thiab hlau ua rau ib leeg thiab tsim chromium carbide. Kev txo qis hauv feem pua ntawm cov pa roj carbon monoxide hauv thawj qhov sib xyaw ua rau muaj kev nce hauv cov txiaj ntsig ntawm Cr7 C3 thiab Cr23 C6 daim ntawv.
Lwm txoj kev rau kev sib txuas chromium carbide siv oxide, ntshiab txhuas thiab graphite nyob rau hauv tus kheej-propagating exothermic cov tshuaj tiv thaiv uas ua raws li hauv qab no:
3Cr2O3 + 6Al + 4C → 2Cr3C2 + 3Al 2O3
Nyob rau hauv txoj kev no, cov reagentscrushed thiab sib tov nyob rau hauv ib lub pob zeb. Cov hmoov tsis sib xws yog ces compressed rau hauv ib ntsiav tshuaj thiab muab tso rau hauv ib qho inert argon cua. Cov qauv yog ces rhuab. Ib lub xov hlau kub, spark, laser, lossis qhov cub tuaj yeem muab cua sov. Ib qho kev tawm tsam exothermic yog pib thiab qhov ua rau lub zog nthuav tawm cov txiaj ntsig thoob plaws qhov seem ntawm tus qauv.
Kev tsim cov chromium carbides
Ntau lub tuam txhab tsim cov khoom siv los ntawm kev sib txuas ntawm aluminothermal txo thiab ua haujlwm nqus ntawm qhov kub ntawm 1500 ° C thiab siab dua. Kev sib xyaw ntawm chromium hlau, oxide thiab carbon yog npaj thiab muab tso rau hauv lub tshuab nqus tsev vacuum. Lub siab nyob rau hauv qhov cub yog txo thiab qhov kub yog nce mus rau 1500 ° C. Cov pa roj carbon ces reacts nrog cov oxide los ua hlau thiab gaseous monoxide, uas yog vented rau lub tshuab nqus tsev twj. Cov chromium ces ua ke nrog cov pa roj carbon ntxiv los ua carbide.
Qhov sib npaug ntawm cov khoom no txiav txim siab cov ntsiab lus ntawm cov khoom tshwm sim. Qhov no tau ua tib zoo tswj xyuas kom ntseeg tau tias cov khoom zoo tsim nyog rau kev lag luam xav tau xws li aerospace.
Kev tsim cov hlau chrome
- Cov kws tshawb nrhiav pom cov chav kawm tshiab ntawm carbides uas tau txais kev ruaj ntseg los ntawm cov qauv tsis sib haum.
- Cov txiaj ntsig ntawm txoj kev tshawb fawb tau tsim lub hauv paus rau kev tshawb fawb yav tom ntej ntawm cov carbides tshiab muaj txiaj ntsig hauv kev siv tswv yim.
- Tsim 2D nitrides yooj yim dua.
Metal thatsiv nyob rau hauv ntau lub tuam txhab, tsim los ntawm aluminothermic txo, qhov twg muaj ib tug sib tov ntawm chromium oxide thiab txhuas hmoov yog tsim. Tom qab ntawd lawv tau thauj mus rau hauv lub nkoj roasting qhov chaw sib tov yog ignited. Aluminium txo chromium oxide rau hlau thiab alumina slag ntawm qhov kub ntawm 2000-2500 ° C. Cov tshuaj no tsim ib lub pas dej molten nyob rau hauv qab ntawm lub firing chamber, qhov twg nws tuaj yeem khaws tau thaum qhov kub thiab txias tau poob txaus. Txwv tsis pub, kev sib cuag yuav nyuaj thiab txaus ntshai heev. Tom qab ntawd cov khoom pib hloov mus ua hmoov thiab siv los ua cov khoom siv raw rau kev tsim cov chromium carbide.
Kev sib tsoo ntxiv
Crushing ntawm chromium carbide thiab nws thawj cov khoom yog nqa tawm nyob rau hauv mills. Thaum sib tsoo cov hmoov hlau zoo, yeej ib txwm muaj kev pheej hmoo ntawm kev tawg. Yog li ntawd, cov mills tau tsim tshwj xeeb los daws cov teeb meem zoo li no. Cryogenic tub yees (feem ntau yog kua nitrogen) kuj tseem siv rau lub chaw kom yooj yim sib tsoo.
Hnav resistant coatings
Carbides yog ib qho nyuaj thiab yog li ib qho kev siv rau chromium yog muab cov coatings muaj zog tiv thaiv rau ntawm qhov chaw uas yuav tsum tau tiv thaiv. Ua ke nrog kev tiv thaiv hlau matrix, ob qho tib si los tiv thaiv corrosion thiab hnav-tiv taus cov neeg ua haujlwm tuaj yeem tsim tau yooj yim rau kev thov thiab raug nqi. Cov txheej txheem no yog tsim los ntawm kev vuam lossis thermal txau. Ua ke nrog lwm cov tshuaj tiv thaiv, chromium carbide tuaj yeem siv rauua cov cuab yeej txiav.
vuam electrodes
Cov chromium carbide rods tau siv ntau dua los ua qhov qub ferrochromium lossis carbon uas muaj cov khoom siv. Lawv muab cov txiaj ntsig zoo dua thiab zoo sib xws. Nyob rau hauv cov vuam electrodes, chromium II carbide yog tsim thaum lub sij hawm sib txuas cov txheej txheem los muab ib txheej hnav. Txawm li cas los xij, kev tsim cov carbide yog txiav txim siab los ntawm cov xwm txheej hauv kev sib koom ua tiav. Thiab yog li ntawd, tej zaum yuav muaj kev hloov pauv ntawm lawv uas tsis pom cov electrodes uas muaj chromium carbide. Qhov no yog tshwm sim nyob rau hauv lub hnav tsis kam ntawm cov deposited weld.
Thaum kuaj lub log ua los ntawm cov xuab zeb qhuav, nws pom tias qhov hnav ntawm cov khoom siv rau ferrochrome lossis carbon electrodes yog 250% siab dua. Muab piv rau chromium carbide.
Cov qauv hauv kev lag luam vuam los ntawm cov nplaum electrodes mus rau cov xaim xaim xaim tau txais txiaj ntsig zoo rau cov khoom. Chromium carbide yog siv yuav luag tshwj xeeb hauv cov khoom pulverized es tsis txhob siab carbon ferrochromium vim nws tsis raug kev txom nyem los ntawm cov nyhuv dilution tshwm sim los ntawm ntau cov hlau nyob rau hauv nws.
Qhov no txhais tau hais tias cov txheej txheem uas muaj cov khoom hnyav dua, uas muaj qhov hnav tsis kam, tuaj yeem tau txais. Yog li ntawd, vim muaj kev hloov pauv ntawm cov pas nrig electrodes mus rau cov xaim xaim xaim vim qhov zoo ntawm automation thiab cov khoom tsim tau ntau dua nrog rau cov khoom siv tom kawg, kev ua lag luam rau carbide yog nce.
Ib txwm siv rau nwsyog: hardfacing ntawm conveyor screws, roj tov khoom hniav, twj impellers thiab dav chromium daim ntaub ntawv uas yuav tsum tau hnav kuj.
Nyob zoo ib tsoom niam txiv kwv tij neej tsa sawv daws.
Thaum tshav kub txau, chromium carbide yog ua ke nrog cov hlau matrix xws li nickel-chromium. Feem ntau, qhov piv ntawm cov tshuaj no yog 3: 1, feem. Cov hlau matrix yog tam sim no los khi cov carbide rau coated substrate thiab muab cov qib siab ntawm corrosion kuj.
Kev sib xyaw ntawm cov cuab yeej no thiab hnav tsis kam txhais tau hais tias cov txheej txheem thermally txau CrC-NiCr yog qhov tsim nyog raws li qhov kub thiab txias hnav. Nws yog vim li no tias lawv tau siv ntau dua hauv kev ua lag luam aerospace. Cov ntawv thov ntawm no yog txheej rau bar mandrels, kub stamping tuag, hydraulic li qub, tshuab qhov chaw, txhuas tivthaiv hnav tiv thaiv thiab kev siv dav dav nrog kev ua haujlwm zoo rau corrosion thiab puas ntawm qhov kub txog li 700-800 ° C.
Lwm txoj rau chrome plating
Daim ntawv thov tshiab rau cov txheej txheem thermally txau ua kev hloov pauv rau cov khoom lag luam nyuaj. Hard chromium plating ua rau lub plhaub hnav-tiv taus nrog lub ntsej muag zoo ntawm tus nqi qis. Chrome plating yog tau los ntawm dipping cov khoom kom saturated rau hauv lub thawv ntawm cov tshuaj tov uas muaj chromium. Ib qho hluav taws xob tam sim no dhau los ntawm lub tank, ua rau cov khoom tso rau ntawm qhov chaw thiabtsim ntawm coherent txheej. Txawm li cas los xij, kev txhawj xeeb ntawm ib puag ncig yog cuam tshuam nrog kev pov tseg cov dej khib nyiab los ntawm kev siv cov tshuaj electroplating, thiab cov teeb meem no tau ua rau tus nqi ntawm cov txheej txheem nce ntxiv.
Chromium carbide txheej muaj hnav tsis kam uas yog ob thiab ib nrab mus rau tsib zaug zoo dua li tawv chromium plating thiab tsis muaj teeb meem pov tseg cov dej khib nyiab. Yog li ntawd, lawv tau siv ntau dua rau cov tawv chromium plating, tshwj xeeb tshaj yog thaum hnav tsis kam yog qhov tseem ceeb lossis cov txheej tuab yog xav tau rau ib feem loj. Nov yog thaj chaw nthuav dav thiab loj hlob sai uas yuav dhau los ua qhov tseem ceeb dua vim tus nqi ntawm kev ua raws li ib puag ncig nce.
Ciav cuab yeej
Cov khoom tseem ceeb ntawm no yog tungsten carbide hmoov, uas yog sintered nrog cob alt los tsim cov khoom tawv heev. Txhawm rau txhim kho lub zog ntawm cov cuab yeej txiav no, titanium, niobium thiab chromium carbides tau ntxiv rau cov khoom siv. Lub luag haujlwm ntawm tom kawg yog los tiv thaiv kev loj hlob ntawm cov nplej thaum sintering. Txwv tsis pub, cov muaju loj heev yuav tsim thaum lub sij hawm tus txheej txheem, uas yuav degrade lub toughness ntawm cov cuab yeej txiav.
