NGHIEN CUU - T R A O B O I
THAM NITO PLASMA XUNG
CHO THEP DUNG CU BEN NONG SKD61
Tham nito plasma cung nhu cac phuong phap tham nito khae li khueeh tan nito vao be mat kim loai tao thanh ldp tham co do (dng cao, kha nang mai mdn tdt. Tham N plasma cd tiu diem nhi/dl dang kiem soat Idp trang, tieu hao it nang laong va than thien moi trudng. Trong nghien cUu nay, mau dUOc tham d thiet bj Eltropuls, P = 250Pa, V= 500V, hon hop khi tham: 80%H2+
20%Nj, T=530°C, t = 6+12h. Cau true Idp tham dUtfc phan tich tren kinh hien vi quang hoc, nhieu xa tia X. Thanh phan %N va
%C phan tich bang may quang phd OES, do do cUng te vi.
ldp tham gdm Fe^N, Fe,N va CrN. Luong %N dat cao nhat khoing 13wt.% tren vimg be mat va giam dan vao Idi; nguoc lai
%C thap d be mat tang dan va dat cUc dai d gan bien gidi Idp tham sau dd giim dan tdi %C cua nen. Chieu day Idp tham tang theo thdi gian tham. Do cdng dat gia trj cUc dai d be mat va giam dan vao Idi. Trong dieu kien tham da neu, de dat chieu sau 0,12- 0,18mm va do ciifng be mat 950-1ISOHV,, can thdi gian tham 6-12h. SUtang do cdng, do ben, kha nang chju mai la nhd cac nitride dUOc hinh thanh phan tan trong nen martensite.
LGidri thieu
Tham nito dang dugc su dung phd bidn nham cai thidn tinh chat vat lieu nhu mai mdn, bdi tron, mdi. Ldp tham bao gdm ldp trang ngoai cflng va ldp khueeh tan lien kdt viing chac vdi ldi. Ldp trang la mdt dai lidn tue cac pha nitride nhu nitride Y'(Fe^N) va nitride E (Fe, ,N), ldp nay khi quan sat dudi kinh hidn vi thi thay mau trang. Ldp nay tuy CO do cimg cao nhung rat gidn, dd bi vd trong qua trinh lam vide. Tidp theo la ldp khudch tan lidn kdt viing chac vai vat lieu ndn, trong ldp nay cd cac nitride kidu Fe^N va Fe^^N,. Trong cae phuong phap tham nito thi tham nito plasma xung la cdng nghd tham tidn tidn nhat vi ngoai yeu to than thien mdi trudng, cdng nghd nay eho phep ban chd
(*) HOANG VINH GIANG (**) LUC VAN THUCWG
tdi da hien tugng nung ndng cue bd, khdng che va tridt tidu hoan toan ldp trang, dieu nay dac bidt cd hidu qua cao khi tham khudn kim loai [1-4].
Dd tham nito plasma can cd ba ydu td: (1) ap suit thip (vai mbar), (2) ngudn didn mdt chidu vai tram vdn, va (3) hdn hpp khi tham N, va H,. Tham dupe tidn hanh trong Id chan khdng, tudng 16 la cue duong - Anode, va san pham la cue am - Cathode. Khi cho didn ap mpt chidu giua tudng Id va san pham, khi tham se bj ion hda thanh cac ion. Co che hinh thanh ldp tham cd the md ta nhu sau: khi nita sau khi bi ion hoa tao ra ion N' mang didn tich duong.
Nhflng ion nay ban pha bd mat chi tidt va giai phdng cac nguydn tfl kim loai (d day la Fe) ddng thdi giai phdng N nguydn tu. Fe phan img vdi N tao thanh FeN trdn bd mat cathode, nitrid nay tidp tue phan img vdi Fe tao Fe,N va Fe,N, cho den khi tao thanh Fe^N.
Thep SKD61 la thep dung cu dupe su dung rpng rai dd chd tao khudn ben ndng nhu khuon dap ndng, khudn dflc ap luc, khudn dfln nhdm. De tang dp cimg, kha nang chiu mdn, va quan trpng hon, kha nang chju moi va tinh tu bdi Iron, vat lieu nay thudng dupe tham nito dac bidl nito plasma .
Da cd mpt sd cdng trinh nghidn cim lidn quan ddn cdng nghd tham N plasma cho thep dung cu dugc cdng bo d nudc ngoai [1-6]. Tuy nhidn it cd cdng bd nao dd cap sau den su phan bd % N, %C trong ldp tham. Nghien cuu nay danh gia chidu sau, dp cflng td vi, td chflc ldp tham, dac
(*) Vien Cong nghe (**) Vien Nghien ciru Ca khi
I d
ve tam, van tdc vdng tang dan, dat den gia tri cue dai tai ban kinh dng thao (theo Povarov[2] tai vi tri cd ban kinh nho han mdt chut so vdi ban kinh dng thao), sau dd giam dot ngdt khi ddn cdt khdng khi.
3> Ket luan
Tir phuang trinh Navie-Xtdc, vdi nhflng gia thidt gan diing CO CO sd trong thuc td chflng ta da xay dung dupe md ninh toan hpc bidu thj quan he phan bd van tde vdng, ap suat tinh theo phuong ban kinh trong xyclon.
^ T h ^ c te, trong xyclon ddng chay phirc tap hon nhidu.
Ludn tdn tai ddng hudng true (uz / 0) va phu thude vao ndng dp pha ran. Gia tri thuc nghidm se cd su khae bidt nhung vdi kdt qua cac phuang trinh trdn lam co so dd tinh toan thidt kd so bp xyclon.
Tidp tue nghien cim ddng chay hudng true, ap dung cho ddng hai pha tao co sd de md phdng ddng chay trong xyclon. •
Tai lieu tham khao:
[1] Lucmg Ngpc Lgi, Co hpc thuy khi img dung. NXB Bach khoa Ha Npi, 2009.
[2] A.H.rioBapoB, rH.apouHKJioHbi, rocropTCXHi.iar. 1961.
T A P C H f C O K H f V l f T N A M SoOl + 0 2 (Tluiii-OI +l)l) luim i o i o
mHTBttesur-KnBAio £)6i
bidt chi ra su phan bd %N va %C dpc chieu sau Idp thim bang each phan tich %N, %C trdn may quang phd phat xa nguydn tir (OES) theo timg lat cit song song vdi bd mat tham. i
2. ThUc nghiem 2.1. Vat lieu tham
Thanh phan vat lieu dugc phan tich trdn may quang quang phd ARL3460 (bang 1), ed thd thay mau tham la vat lieu tuong duong thep ben ndng SKD6I (JIS 4404).
Bang 1: Thanh phan vat lieu tham
Mau Mau tham
SKX)61 Tieu chuan
C 0,400 0,32 0,42
Si 0,956 0,80 1,20
Mn 0,405 max 0.50
Cr 4,895 4,50 5,50
Mo 1,190 1,10 1,50
v
0.801 0,80 1,20
P 0,020 Max 0,03
s
0,0013 Max.
0,03
Mau tham dugc cat bang may cat day vdi kich thude 20x20x10mm. Mau dugc mai thd trdn may mai 2 da sau dd mai tidp bang giay rap do min 1500. Trudc khi tham, mau dugc nhiet luydn: tdi I050°C/15 phflt, lam ngudi bang khi nen, ram 570°C/2h lam ngudi khdng khi; dp cung dat dupe 44-48HRC
2.2. Tham N plasma
Bd mat mau dupe lam sach bang cdn dam bao khdng bi dinh son hoac dau, md va cac chat ban khae.
Mau dugc tham trdn thidt bj Eltrropul H4580 tai Vidn Nghidn cim Co khi cd thdng sd sau:
- Kich thude khoang khdng lam vide: 0 450 x 800 mm - Didn ap/tin sd max/ddng xung: 0-600V/10 kHz/O^SA - Cdng suat gia nhidt/edng suat plasma: lOkVA/1 Ok VA Cac thdng sd chinh cfla qua trinh tham nhu sau:
- Ap suit: 250 Pa, didn ap: 500V
- Khi thim: hdn hpp khi N^ va H^ 99,999%, do Cdng ty Messer Hai Phdng cung cap.
Qua trinh tham gdm 3 giai doan:
(1) tang nhiet va lam sach bd mat bang phun xa (sputtering),
(2) thim N (khi thim 80%Hj+ 20%N2, nhiet dp T=530°C, thdi gian t= 6-I2h),
(3) ngudi cflng Id ddn nhiet dp khoang 200oC, sau dd lay mau ra ngudi ngoai khdng khi.
Vm dieu chinh ip suit Lip durang trinh d i i u k h i h
2.3. Kilm tra tinh chat Idrp tham
Dp cung td vi bd mat ciing nhu dpc theo chieu sau ldp tham dugc do trdn mau dugc mai bdng. Thidt bj la may do dp cung td FM-700e, FUTURE-TECH, (Nhat Ban), tai trpng 500g. Dp cung dpc theo Idp tham dugc do vdi khoang each dpc theo chidu sau Idp tham la 20nm.
Chidu day va td chiic kim tuong Idp tham dugc kidm tra trdn mlu mai bdng tam thye bang 2%Nital tren kinh hidn vi quang hpc NIKON, (Nhat Ban) vdi dp phdng dai 200x va 500x.
Ham lugng %N va %C dugc phan tich bang may quang phd phat xa nguydn tu ARL 3460 cd chuang trinh phan tich ham lupng % N trong thep. Ham lugng %N va
%C phan bd theo chidu sau Idp tham dugc phan tich theo timg ldp, khoang each giira cac mat phan tich (song song vdi bd mat tham) la 20pm.
Nhidu xa Rongent (XRD) dugc tidn hanh vdi gdc quel 6 - 2q. Buc xa tia X: Cu k^, X = 1,54056 A, trdn thidt hi D5000 do hang SIEMENS,''(CHLB Dure).
3. Ket qua va thao luan
3.1. Sir phan bo %N va %C theo chieu sau lop tham Su phan bd %N dpc theo chidu sau ldp tham dugc trinh bay trdn hinh 2. Tir kdt qua nay, cd the khang dinh N da khudch tan vao bdn trong bd mat thep, ham lugng N giam dan tir ngoai bd mat vao trong Idi. Ngay trdn bd mat ham lupng %N rat cao, khoang I2%N. Phan tich ky han d bd mat cho thay cd su thay ddi dot ngdt %N trong khoang 5|im tu be mat. Dd bidt chinh xac hon su thay ddi nay can cd thidt bi cung nhu su nghidn cuu cdng phu hon.
Su phan bd %C thi ngugc lai vdi %N (xem Hmh 3).
12
£ 10
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E 4
0
I" —»-l2h L —•—lOh I - * - 8 h
• - T - 6 h
. 1 .. T ^ ^ T - J y ^ ^ T — . 0 40 81) i:0 160 200
Chi6u sSu lop th§m,
Hinh 2: Su phan b6 %N theo chiiu siu lop thim
i :
^ 10 2 8
cn c
^ ft b
1 ^
2 0
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• — • — C y * ^
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0.6
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X a i
Hinh 1; So dd 16 thim N plasma Eltrropul H4580
0.0 0 .<0 100 150 200 250
Chieu sSu lap tham.
Hinh 3: Si/ phan b8 %N-C theo chiiu s i u I6p thSm (10h)
TAP CHf CO KHf V I | T NAM • .s6 01 +02 (Thang 01 -1-02) nain 2010
NGHIEN CUU - T R A O O O I
^Minh 3 cho thay cd su phan bd lai ham lugng %C so vdi vat lieu ndn ban dau. Ham lugng C trdn bd mat tham giam so vdi vat lieu ndn va tang dan vao phia trong ldi, dat gia tri cue dai (cao ban gia tri ban dau cfla vat lieu ndn) ngay trdn bidn gidi ldp tham va ndn. Cd the giai thich la N khudch tan vao bdn trong da thay chd cfla C trong martensite ndn va C bj "day" vao phia trong tap trung d bien gidi ldp tham va ndn lam C tang cao hon ndn.
3.2. D9 cirng te vi theo chieu sau Idp tham
Hinh 4 bidu didn su phan bd dp cflng theo chidu sau ldp tham vdi cac thdi gian tham khae nhau. Cd thd thay dp cimg ldp tham cfla tat ca cac mau (tham 6-12h) trdn viing bd mat nam trong khoang 900-1150HV^5 sau giam dgt ngdt va dat ddn gia tri dp cimg ndn.
Q JO m i;o iwi
Chieu sau lap tham,
Hinh 4: S a phan bii 36 ci>ng doc chieu sau lap tham
33. Anh hudng ciia thdi gian tham den chieu sau Idp tham v^ dg cung be mat
Chidu sau ldp thim dugc xac dinh dua vao dp cung td vi dpc ldp thim (hinh 4) va phan tich %N dpc ldp tham (hinh 3). Tdng chidu sau ldp tham cd thd xac djnh la khoang each tu bd mat thim ddn vi tri ma dp cflng bang do cimg ndn hoac khi %N=0, hai kdt qua nay tuong ddng vdi nhau. Chidu sau ldp thim phu thude vao thdi gian, tham cang lau thi ldp thim cang day, didu nay phfl hgp vi qua trinh thim la qua trinh khudch tan (5~t"'). Be chgn dugc thdi gian thim hpp ly, kdt qua da ndu cd y nghia quan trpng giup dinh lupng dupe thdi gian tharn sao cho vira du. Dd thj bidu dien quan he thdi gian va chidu sau ldp thSm (hinh 5) cd thd giup chflng ta xac dinh thdi gian thim hgp ly cho timg img dung cu thd.
£ a S i»
^ no
Thdi gian tham. [h]
UnliS Chi4u«au ldp thim viltidi gian thSrr
Thdi gian tham. [h]
Hnli 6 06 ci/ng b« mSt va Ihfti gian lham
Kdt qua dp cung bd mat va thdi gian tham dugc trinh bay tren hinh 6. Thdi gian thim trong khoang 6-12h khdng anh hudng nhidu ddn do cimg bd mat va do cirng nay dao j^png trong khoang 1000-1150HV„5. Cd thd thiy (hinh 6)
dp cung tdi da dat dupe khi thdi gian tham trong khoang 8-lOh (T=530°C), keo dai thdi gian dp cimg nay cd xu hudng giam.
3.5. To chirc Idp tham
Quan sat mau tam thuc 2% Nital trdn kinh hidn vi quang hpc dp phdng dai 100-500x thay mdt vflng tdi khoang 120-170nm sat bd mat tham, day chinh la ldp tham, kdt qua nay phfl hop vdi chidu day ldp tham xac dinh bang do dp cung td vi hoac %N. Khdng quan sat thay ldp trang, keo dai thdi gian tham ddn I2h thay xuat hidn dau dd ldp trang rat mdng 1-2 ^im. Hinh 7 la td chflc mpt ldp tham didn hinh, cd thd thay cac pha hoa ben phan tan ddu trong ndn martensite, tidp den la pha a. Phd XRD (hinh 8) cbo thay pha nay la £-Fe3N, Y'-Fe4N, day la cau true dac tnmg cfla mdt ldp tham nito dat ydu cau vd chat lugng.
Hinh 7:16 chirc l^ vi lap thim oM) "C/8h, 500x, 2%Nital)
i
l l
niil bi do: SIEMENS D5000 VIlli^uSKMI.
BuocM^: I M06A.
B<M< l)U«: 0 03-
il
o ...
z z.
' ^ .
JL
.Ji.J^J\^^Hinh 8: Phd nhieu xa Rcmgen th4m N plasma 530oC/8h
4. Ket luan
1. Thim N plasma dua N vao bd mat vdi su pban bd
%N dat cao nhit khoang 12-13wt.% trdn vung bd mat va giam din vao loi. Qua trinh nay lam phan bd lai %C trong ldp thim: %C giam (so vdi %C vat lieu ndn) d vflng bd mat va tang d vflng bidn gidi giira ldp tham va ndn.
2. c i u true ldp thim bao gdm cac pha E-Fe^N, y'-Fe^N phan tan trong ndn martensite, tidp theo la pha a, day la ciu true dae trung cfla mdt ldp tham nito dat ydu eau ve chat lupng.
3. Chidu day ldp thim tang vdi thdi gian tham. Dp cung dat gia tri cue dai d vung bd mat va giam dan vao ldi. Trong didu kidn tham da ndu, dd dat chidu sau 0,12- 0,18mm va dp cung bd mat 950-1 ISOHV^j^ can thdi gian tham 6-I2h.
Vdi td ehuc ldp thim nhu trdn, dp ben. kha nang chju mai, chiu mdi cfla vat lieu se tang va nhu the lam tSng
T A P C H f C O K H f V l f T N A M • .Sc', 0 1 + 0 2 ( T h a i i g O l + 0 2 ) n a m 201o
NGHIEN CLTU - T R A O B O I
tudi thp cfla khudn. Tham N plasma cho khudn bdn ndng va theo ddi tudi thp cfla khudn la npi dung dang dupe tidn hanh. •
Tai lieu tham khao:
[1] Mehmet Capa, Muzaffer Tamer, Life Enhancement of Hot -Forging Dies by Plasma Nitriding, Turk J. Engin
Environ Sci. 24 (2000), 111-117.
[2] Insup Lee, Ikmin Park, The effect of processing temperature and time on the surface properties of plasma-
radical nitrided SKD61 steel.
Journal of Ceramic Research 2 (2006), 132-135
[3] M.B. Karamis, Some sffects of the plasma nitriding process on layer properties, Thin Solid Films 217 (1992),
38-47.
[4] E. J. Miola, Near surface composition and microhardness profile of plasma nitrided H 12 tool steel, Materials
Science and Engineering A256 (1998), 60-68
[5] M. Sokovic, Improvement of Tool Life of Die-casting Tools with Duplex Treatment.
Int. J. Microstructure
and Materials Properties 2 (2006).
[6] Patama Visuttipitukul, Characterization of plasma nitrided AISI H13 tool steel, Acta Metallurgica Slovaca,
12(2006), 264-274 [7] M. Yan, Matematical Models and Computer Simulation of Nitrogen Concentration Profile in Pulse Plasma
nitrided Layer, J. Materials Science and Techonlogy 19 (2003), 164-166.
G o a x D U n s M j m s i i i i r D ^ ^
•u®M<io?(aM(2H^'uiiaiJE{] @S?i
TAO PHOI TREN CO S 6
CO HOC CAC MOI TRlTOfNG LIEN TUC
(*) TS. LUtJ QUANG HI
Qua trinh tao phoi da diTcrc nhieu tac gia nghien cihi vdi cac phifcmg phap nghien ciiru truyen thong, da diTtfc trinh bay trong nhieu giao trinh ve cat got kim loai. Bai bao nay trinh bay phaotng phap tiep can mdti nghien cijfu qua trinh cat got, tren ctf sd coi qua trinh cat gpt tao phoi nhiT la mot bai toan trong ly thuyet ctf hoc cac mdi trudng lien tue. PhUtfng phap tiep can nay cho phep nghien cdu qua trinh cat got tao phoi va cac hien tUtfng ctf ly xiy ra trong dd dddi cac gdc do mdi dang chu y.
1. Gidi thieu
Khi ndi ddn ddng vat lieu bidn dang deo khi tao phoi thi mudn ndi rang bidn dang va img suat phai dfl ldn dd phoi hinh thanh. Do cdng co hpc (dugc cung cap bdi chuydn ddng cua dao) chuydn thanh nhiet va do dd lam tang nhiet dp vung bidn dang, nhiet dp tai vflng bidn dang lai cd anh hudng rat cu thd ddn qua trinh cat gpt. Vi thd qua trinh cat gpt dupe xet cu thd hon nhu la mdt bai toan co nhiet, khi dd theo Iy thuydt co hpc cac mdi trudng lidn tue, ydu cau can giai mpt bp cac phuong trinh sau: phuong trinh lidn tue; phucmg trinh chuydn dgng; phuong trinh can bang nang lugng; phuang trinh Clausius-Duhem; phuong trinh cau true vat lieu. Dd cd dugc ldi giai cua cac phuang trinh nay, can phai cu the hoa cac didu kidn bidn va didu kidn ban dau.
2. Mo hinh qua trinh cat got
Hinh 1 la so dd hoa cua md hinh, trong do: a,- chidu day cat; y- gdc trudc dao; b,- chidu rdng cat; a- gdc sau dao; a,- chidu day phoi; v- toe dp cit; b,- chidu rdng phoi;
Vp- tdc dp phoi; l^- chidu dai tidp xuc phoi-dao trdn mat trudc dao.
Cac gia thiet ban dau nhu sau: tdc dp cat la khdng ddi; chidu rdng cat b, Idn hon chidu day cat a, va ca a, va b, deu khdng ddi; ludi cat sac tuyet ddi;
phoi la dai lidn tue; vecto tdc dp cat V vudng gdc vdi ludi cat; vat lieu phdi ddng nhat, dang hudng va khdng nen dugc; phdi d nhiet dp trong phdng;
cat gpt trong khdng khi (khdng diing dung dich tron ngudi); khdng eo mai mdn trdn dao; dao la vat thd cung vung, chieu rgng dao b^ ldn hon b,; trang thai cat gpt didn ra lien tue.
Hinh I
' • TAP CHf CO KHf VI§T NAM • So 0 1 + 0 2 rThani. 01+02") nam 2010
(*) Truomg DH Su pham Hk Npi
