NGHIEN CUU • TRAO DOI
Ung dung cong nghe tham nitcf plasma
cho mot so cM tik may che tao ti^ thep hop kim crom
(*) HOANG VINH GIANG (**) LUC VAN THirONG (***) HOANG MINH THUAN
Tom t a t ; SU phan bo % N , do cuTng te vi dpc ldp t h a m , chieu sau, cau true pha cua I6p t h a m N plasma cua m l u t h e p htfp kim Cr cao (SKD11), Cr t r u n g binh (SKD61) va hcrp k i m t h a p (40CrMo, 20CrMo) dUOc kiem tra va danh gia. Qua t r i n h t h a m dUcrc t i e n hanh tren t h i e t bj Eltropuls, vdi P = 250Pa, V= 500V, hon hop khf t h a m : 75%H2+
25%N2, T=530°C, t = 8 h . M o t so chi tiet may nhU banh rang, true rang, khuon ben n o n g , k h u o n ben nguoi dUorc t h a m N plasma co t u o i t h o tang khoang 1,5 lan.
1. Gioi thieu
Tham nito plasma dugc tien hanh trong Id chan khdng, tudng Id la cue duong - Anode, va san pham la cue am - Cathode. Khi cho dien ap mdt chieu giiia tudng Id va san pham, khi tham se bi ion hda thanh cac ion. N* khuech tan vao be mat vat tham tao thanh cac nitride ciing lam cai thien tinh chat vat lieu nhu mai mdn, bdi tron, mdi.
Vat lieu cd tinh tham tdt la nhirng vat lieu cd ehiia cac nguyen td hgp kim ed ai luc manh vdi N nhu AI, Cr, V, Mo, Ti. Tinh chat cua ldp tham phu thudc rat nhieu vao thanh phan % cac nguyen td hgp kim.
Bai bao nay danh gia chieu sau, do ciing te vi, td chuc ldp tham cua 3 loai thep hgp kim vdi ham lugng
%Cr khac nhau, dd la: thep hgp kim Cr thap vdi l%Cr (20CrMo, 40CrMo), Cr trung binh 5%Cr (SKD61) va Cr caol2%Cr(SKDll).
2. Thirc nghiem
2.1. M a u thi nghiem
Man tham duge cat bang may cat day \ai kich thudc 20x20x10mm. Mau dugc mai thd tren may mai 2 da sau dd mai tiep bang giay rap do mm 1500. Trade khi tham, mau dugc tdi va ram dat do ciing nhu trong bang 1.
Bang 1: Thanh phan va do ciing mau tham
40CrMo SKD61 SKDll
C 0,40 1,45 0,40
Si
0,17 0,26 0,95
Cr 1,0 11,5 4,90
Mo 0,16 0,85 1,19
V 0,01 0,21 0,80
HRC 28-32 45-50 56-60
(*) Vien Cong nghe. Ha Noi (**) Vien Nghien cim Co khi, Ha Noi
(•"' Trudng Cao ding ngh^ Uong Bi, Quang Nuih
2.2. Cong nghe tham N plasma
Be mat mau duge lam sach bang edn dam bao khdng bi dinh son hoac dau, md va cac chat ban khac. Mau duge tham tren thiet hi Eltrropul H4580 tai Vien Nghien ciiu Co khi.
Cae thdng sd chinh cua qua trinh tham:
- Ap suSt: 250 Pa , dien ap: 500V
- Khi tham: hon hgp khi N^ va H^ 99,999% eua Cty Messer Hai Phdng.
Qua trinh tham gdm 3 giai doan:
(1) tang nhiet va lam sach be mat bang phim xa (sputtering),
(2) tham N (khi tham 75%H,+ 25%N„ nhiet do T=530°C, thdi gian t= 8h)
(3) ngudi ciing Id den nhiet do khoang 200°C, sau do lay mau ra ngudi khdng khi.
2.3. Kiem tra tinh chat ldp tham
Do Cling te vi be mat ciing nhu doe theo chieu sau ldp tham dugc do tren mau dugc mai bdng. Thiet hi la may do do eiing te FM-700e, FUTURE-TECH, Nhat ban, tai trgng 500g. Do ciing doc theo ldp tham dugc do vdi khoang each dgc theo chieu sau ldp tham la 20-25nm
Chieu day va td chiic kim tuong ldp tham dugc kiem tra tten mau mai bdng tam thuc bang 2%Nital tren kinh hien vi quang hgc.
Ham lugng %N dugc phan hch bang ma>' quang phd phat xa nguyen tu' ARL 3460 cd chuong trinh phan tich ham lugng % N trong thep. Nhieu xa Rongent (XRD) dugc tien hanh tren thiet bi D5000 do hang SIEMENS. CHLB Dire.
TAP C H i c a K H i VIET NAM •*• So 05 - Tliang 5 nam 2010
NGHIEN CUU - TRAO DOI
3. Ket qua va ihig dung
3.1. Ket qua phan bo N trong lap tham
Khi phan tich ngay tren be mat %N rat cao (10- 14%N), tuy nhien khi mai het khoang 2-5pm, ham lugng
%N giam han. Do cd su thay ddi rat nhanh ve %N nen chung tdi tien hanh mai vdi chieu sau be hon tren be mat de cd cai nhin chinh xac hon ve sir phan bd.
Dd thi phan bd dugc the hien tren hinh 1. Cd the nhan thay, ddi \di thep SKDl 1 \ a SKD61 cd ham lugng Cr cao.
do ai luc giira Cr va N cao nen hinh thanh nhieu nitride crdm can tro su khuech tan cua N vao ben trong, do dd N khuech tan se tap trung o' ldp ngoai cimg. Cdn ddi vdi thcp hgp kim thap 40CrMo, lugng %N tren be mat cao nhung do qua trinh khuech tan N ao ben trong de dang hon nen
%N doc theo ldp tham keo dai va giam tir tir.
0 50 100 150 200 250 Chieu sau lop tham
Hinh 1: Sir phan bo %N doc theo chieu sau ldp tham vdi thdi gian tham 8h
3.2. Do cuTig te vi doc theo chieu sau lop tham
Do Cling te vi doe theo ldp tham dugc tien hanh do tren mat cat ngang qua ldp tham vdi khoang each 25|Lim, ket qua phan bd nay the hien tren hinh 2
)6 Cling HV 0.5 ^ 8 1 §
-* SKD11 . 40CrMo S K D 6 l |
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100 150 Chieu sau lap tham
Co the nhan thay thep hgp kim thap co do cung be mat thap nhat (750HV), trong khi do thep hgp kim Cr cao SKDll CO do cung cao nhat (1150HV). Chieu sau lop tham thi ngugc lai, thep hgp kim Cr thap dat dugc lop tham cao nhat, con thep hgp kim Cr cao SKDll co lap tham thap nhat.
3.3. To chirc te vi va chieu sau lap tham
Cau true pha be mat ldp tham dugc xac dinh bang nhieu xa Rongent (XRD) vdi gdc quet 0 - 20. Biic xa tia X:
Cu k , )u = 1,54056 A, ket qua dugc the hien tren hinh 3
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55 beThiet bi do: SIEMENS D5000 V9tlieu:SKD6l, Birac song: 1.5406A, Buoc quel: 0.03°
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Hinh 2: Su phan bo do ciing trong ldp tham
Hmh 3: Nhieu xa XRD
Cau tnic pha ldp tham bao gdm pha e-Fe^- N, y'- Fe^N, pha a, day la cau true dac trung ciia ldp tham nito dat yen can chat lugng.
TAP CHI c a KHI VIET NAM V So 05 - Thang 5 nam 2010
NGHIEN Cl/U - TRAO 001 Chieu sau ldp tham ed the xac dinh dua vao su phan
bd %N hoac su phan bd do ciing theo chieu sau ldp tham.
Ngoai ra, chieu sau ldp tham cd the xac dinh bang each quan sat tren kinh hien \ i.
Vdi 3 phuong phap \iia neu cd the xac dinh tuong ddi chinh xac chieu sau ldp tham. Ket qua chieu sau ldp tham cua timg loai thep dugc the hien trong bang 2
Bang 2: Chieu sau ldp thlm, T=530°C, t = 8h
Chieu sau ( m)
iOCrMo 270
SKD61 120
SKDll 80
3.4. U n g dung tham mot so chi tiet may Dudi day la mdt sd chi tiet dugc tham N plasma tai phdng thi nghiem CN ban \ a xu ly be mat - Vien Nghien Cliu Co khi.
4. Ket luan
1) Trong qua trinh nghien cuu da xac dinh dugc mdt so thdng sd chinh trong qua trinh tham ni-to xung plasma la: Nhiet do, ap suat, dien ap, thanh phan hon hgp khi,.. day la nhung yen td quyet dinh true tiep tdi chat lugng chi tiet \ e do ciing. do chiu mai mdn \ a ehieu sau ldp tham
2) Thep hgp kim Cr cd ham lugng r/o-12%Cr duge tham N plasma cho cau tnic ldp tham bao gdm ngoai ciing la ldp trang chiia pha e-Fe,-3N, y'-Fe^N ed chieu day khoang 2-5 tn, tiep den la ldp khuech tan gdm cae nitride phan tan trong nen martensite.
3) Ham lugng %N fren be mat cao khoang 12% nhung giam dot nggt, rieng thep hgp kim thap sau khi cd su sut giam dot nggt xudng klioang 0,9%N, sau dd %N giam hi tir ddn gia tri 0, \img khuech tan cua thep nay dugc md rdng.
4) Ham lugng Cr cang cao chieu sau ldp tham cang thap do cd su hinh thanh CrN lam can trd qua trinh khuech tan.
5) Da tien hanh irng dung tham mdt sd chi tiet may nhu: true rang banh rang, nap van trong he thdng bom dau thuy luc (che tao tii thep hgp kim thap) khuon diic, khudn ren (che tao tir thep SKD61), khudn dap, khudn eat (che tao tii thep SKDll). Cac san pham tren sau khi dua vao su dung tudi thg tang khoang 1.5 lan \a duge ngudi su dung chap nhan.
LM cam cm
Cdng trinh nay dugc thuc hien \ di su hd trg \ e kinh phi ciia chuong trinh KH&CN trgng diem cap nha nude
\ e Nghien ciiu, phat trien \ a iing dung cdng nghe vat lieu KC.02./06-10 •
Tai lieu tham khao:
1. Insup Lee, Ikmin Park. The effect of processing temperature and time on the surface properties of plasma-radical nitridcd SKD61 steel.
.loumal of Ceramic Research 2 (2006). 1.^2-135
2. M.B. Karamis, Some sffects of the plasma nitridmg process on la\er properties. Thin Solid Films 217 (1992). 38-47.
3. E- .1. Miola, Near surface composition and microhardness profile of plasma nitrided H 12 tool steel. Materials Science and Engineering A256 (1998). 60-68
4. Bojan Podgomik. Wear resistance of plasma and pulse plasma nitrided gears
5. M. Yan. Matematical Models and Computer Simulation of Nitrogen Concentration Profile in Pulse Plasma nitnded Layer. .1.
Materials Science and Techonlogy 19 (2003), 164-166.
Sd 05-Tiling 5 nam2010