Felületmódosítás
Korszerű anyagok és technológiák, MSc
2013
A felületi tulajdonságok tudománya: átfogó
(interdiszciplináris) terület
• A felület a tiszta fizikai és kémiai tulajdonságok szemszögéből.
• Topográfiával kapcsolatos tulajdonságok (felületi érdesség).
• Tágabb értelemben: „surface engineering”: komplex nézőpont
• Kapcsolat a felületi tulajdonságok, az alkalmazás és az
alkalmazott technológiák között.
• (Tiszta fizikai és kémiai tulajdonságok: alapkutatás szemszöge.)
• A felületek tulajdonsága a felhasználók szempontjából: „surface
engineering”.
Kondenzált anyagok nagy fajlagos felülettel:
a „komplexitás” alapja a felület
•
•
Felületi tulajdonságok kialakulása ← klaszterek tulajdonsága (mérethatás):
„Méretfüggő” tulajdonságok: átmenet az önálló atomtulajdonságok és a
termodinamikailag stabil makroszkópos tulajdonságok között;
A redukált ionizációs energia különböző szabadfelületű fémklaszterek esetében a klaszterátmérő
reciprokának függvényében
Aim: the local modification of surface properties changing either the local
composition or the structure or both of them.
The desired surface properties are often contradict to those in the bulk! (i.e. local
hardness, local corrosion resistance)
examples: development of peculiar compositional relations on the surface of
semiconductors
The development of hard, wear- or corrosion-resistant surfaces on cutting,
drilling tools
Development of optical or decorative layers
Two alternatives:
Covering the surface with protective layer (corrosion resistant layers)
Structural or compositional changes in the surface layer
Traditional methods
Increase of non-metallic element concentration in
the surface layer, using heterogeneous reaction.
i.e. iron/steel heating in appropriate gas-mixture
(carbonization, decarbonization, nitridation)
CH4  [C]Fe + 2H2
CH4/H2
2NH3  [N]Fe + 3H2
NH3/H2
Layer deposition using electrochemical or chemical methods
Hard chromium-layer (3-500 μm, HV 900-1100)
Ni-P amorphous layer (3-30 μm, HV 1300)
Surface hardening using inductive heating and subsequent rapid
cooling
Inductor
Inductor
Cog wheel
Cog wheel
forrás: Szurdán Szabolcs
Deposition of thin layers by physical methods (Physical Vapour
Deposition, PVD)
•
favour:
•
•
High melting point metals can be deposited to low substrat temperature because
T substrat can be low
•
The electrical conductivity of substrate not necessary
•
Complex multilayers can be deposited
•
Alloy deposition is also possible
•
„clean technology” (without the formation of products causing environmental pollution)
•
limits:
•
Expensive (vacuum circumstances)
PVD (physical vapor deposition)
The original, traditional technologies: chemical reactions are not included ( i.e. mirror production)
Heating
Substrate
Source
Vacuum system
Schematic illustration of the
principle
Chamber
Substrate holder
Mask
Window
Cover plate
Layer thickness
measure
Valve
Evaporate
source
Freezer
Diffusion
pump
Pre-vacuum pumps
The technical arrangement
Crucial in every deposition is the layer duration, which is influenced mainly by the surface preparation (cleaning)
Physical Vapour Deposition
Source: Platit
0,1
0,2
0,3
0,4
0,5
0,6
0,7
Ts/Tm
The real structure of the deposited layer versus the substrat
to melting point temperature
Deposition of TiN layer on the surface of tools
for the purpose of surface hardenening
The dimensions
Source: Platit
Some another exmples
Source: Platit
Machined length [m]
Machined length [m]
Cutting speed [m/min]
Feed [mm/rev]
The machined length versus the main machining parameters: cutting speed (a)
and feed (b) ( • TiN coated, o TiN coated and newly grinded, □nitride coating ■ without coating
Chemical Vapour Deposition, (CVD)
basic principles
In the original form, the procedure consist of two isothermal reactions:
a.)
at T1 temperature
M +nXMXn
(M layer forming metal , X halogen) At T1
a volatile compound is
formed
b.)
at T2 (T2 > T1 )
MXnM + nX
Thermal decomposition of MXn occur on the substrate surface
Subsequently the decomposition process, the halogen molecule is
circuated (in order to form new volatile molecules)
Typical chemical reactions in the CVD procedure:
Metal-halogenides are often used as precursor materials in these
techniques.
The reason: volatile compounds (high tension even at low temperatures!)
(see tables)
Besides the metal-layer depositions, the method also used for compound
depositions (refractory carbides, silicides, borides)
Typical CVD reactions
CrI2(g)
800-1000 ºC 
Cr(s) + 2I(g)
WF6(g) + 3H2(g)
350-1000ºC 
W(s) + 6HF(g)
WCl6(g) + 3H2(g)
500-1100ºC 
W(s) + 6HCl(g)
TaCl5(g) +5/2 H2(g)
700-1100ºC 
Ta(s) + 5HCl(g)
(C8H10)2Cr(g)
400-600ºC a 
Cr(s) + 2C8H10(g)
Ni(CO)4
150-200ºC b 
Ni(s) + 4CO (g)
Al2Cl6(g) + 3H2O(g)
800-1400ºC 
Al2O3(s) + 6HCl(g)
BCl3(g) + NH3(g)
500-1500ºC 
BN(s) + 3HCl(g)
TiCl4(g) + CH4(g)
800-1100ºC 
TiC(s)+ 4HCl(g)
Ga(g) + AsCl3(g) + 3/2H2(g)
750-900ºC 
GaAs(s) + 3HCl(g)
Typical reactants, processing parameters for a few depositions
Typical reactants,
processing
parameters for a few
depositions
layer
reactant
Add.
reactant
T (C)
pressure
(kPa)
Deposition
velocity
(nm/min)
W
WF6
WCl6
WCl6
W(CO)6
H2
H2
-----
250-1200
850-1400
1400-2000
180-600
0,133-100
0,133-2,67
0,133-2,67
0,0130,133
0,127-50,8
0,254-38,1
2,54-50,8
0,127-1,27
Mo
MoF6
MoCl5
MoCl5
Mo(CO)6
H2
H2
-----
700-1200
650-1200
1250-1600
150-600
2,67-46,7
0,133-2,67
1,33-267
0,0130,133
1,27-30,5
1,27-20,3
2,54-17,8
0,127-1,27
Re
ReF6
ReCl5
NbCl5
NbCl5
NbBr5
H2
--H2
--H2
400-1400
800-1200
800-1200
1880
800-1200
0,133-13,3
0,133-26,7
0,133-100
0,133-2,67
0,133-100
1,27-15,2
1,27-15,2
0,076-25,4
2,54
0,076-25,4
Nb
NbCl5
NbCl5
NbBr5
H2
--H2
800-1200
1880
800-1200
0,133-100
0,133-2,67
0,133-100
0,076-25,4
2,54
0,076-25,4
Ta
TaCl5
TaCl5
H2
---
800-1200
2000
0,133-100
0,133-2,67
0,076-25,4
2,54
Zr
ZrI4
---
1200-1600
0,133-2,67
1,27-2,54
Hf
HfI4
---
1400-2000
0,133-2,67
1,27-2,54
Ni
Ni(CO)4
---
150-250
13,3-100
2,54-38,1
Fe
Fe(CO)5
---
150-450
13,3-100
2,54-50,8
V
VI2
---
1000-1200
0,133-2,67
1,27-2,54
Cr
CrI3
---
1000-1200
0,133-2,67
1,27-2,54
Ti
TiI4
---
1000-1400
0,133-2,67
1,27-2,54
The important metals and ceramics produced by the CVD method
Metals
Cu, Be, Al, Ti, Zr, Hf, Th, Ge, Sn, Pb, V, Nb,
Ta, As, Sb, Bi, Cr, Mo, W, U, Re, Fe, Co, Ni,
Ru, Rh, Os, Ir, Pt
Graphite carbides karbon
C, B4C, SiC, TiC, ZrC, HfC, ThC, ThC2,VC,
NbC, Nb2C, TaC, Ta2C, CrC, Cr4C, Cr7C3,
Cr3C2, MoC, Mo2C, WC, W2C, VC2, V2C3
Nitrides
BN, TiN, ZrN, VN, NbN, TaN, Si3N4
Boron and borides
B, AlB2, TiB2, ZrB2, ThB4, ThB, NbB, TaB,
MoB, Mo3B2, WB, Fr2B, FeB, NiB, Ni3B2,
Ni2B
Silicon and silicides
Si és Ti, Zr, Nb, Mo, W, Mn, Fe, Ni, Co and
varies silicides
Oxides
Al2O3, BeO, SiO2, ZrO2, Cr2O3, SnO2
Examples for the compound-layer deposition
• The TiN layer deposition:
• 2 TiCl4 +4 H2 +N2  2 TiN +8HCl
• Al2O3 layer deposition:
• 2AlCl3 +3CO2 +H2  Al2O3 +3CO +6HCl
Halide preparatory
Gases
Gas mixer
Outgoing gas cleaner
and neutralizer
Vacuum
pump
Programming
unit
Heating bell
Heating bell
Gas supply
Heating
controller
Deposition chambers
The scheme of complete unit for CVD technology
The properties of deposits produced by CVD ,
layer-substrate: the compatibility
Favour: -high temperature: deposit accomodat even the complicated,
irregular surfaces (inner surfaces can be covered)
Another example
Tantállal bevont gégecső
The limits:
•
•
The high substrat temperature (for example for structural or carbon steels is
not recommended! 6-800 oC!)
Expensive reactants
Gyémánt és gyémántszerű amorf rétegek
DLC: Diamond-Like Carbon
Polymer
DLC
Graphite
Diamond
The properties of CVD-produced policrystalline diamond layers:
high chemical resistance, high hardness, high wear resistance, low frictional
resistance
Hardness and young moduli of carbon- based coated layers
Me: fém az elektromos
vezetőképesség növeléséhez, fémkarbidok
H: hidrogéntartalom a C2H2
elbomlásából
a: amorf fázis tartalmú réteg
Si: szilíciumtartalom
i-C: mátrix sp3-as kötésekkel, de
amorf
The techniques of plasma spraying
Plazmagáz energiatartalma
Helium
Hővezetési tényező
Shematic drawing of plasma spraying and the
SEM photograph of the sprayed coating
Characteristics of plasma-sprayed layers
Improvement of
•Abrasive properties
•Hardness
•Corrosion resistance
•(Especially in those cases, when the
base material is low-cost
•improvement of bio-compatibility
(implanted parts)
Succesfully applied for
•the surface improvement of carbonsteels
•surface hardness increase
•corrosion resistance increase
The modes of plasma welding:
inner, outher wire supply, powder supply
The laser surface treatments
[%]
Absorption degree
Abszorpciós
fok [%]
0.25
Al
CO22 laser
CO
lézer
Diode laser
Dióda
lézer
Nd::YaG laser
Nd:YAG
lézer
laser
Excimer lézer
Excimer
0.35
30
0.3
Excimer laser
The effectivity highly depends on the
absorption degree
Iron
Acél
Cu
Au
Fe
20
0.2
0.15
10
0.1
Mo
0.05
Ag
0
0.1
1
Wavelength (m)
Hullámhossz
[m]
10
The absorption degree of various laser beams as a
function of wavelengths
100
The absorption degree also depends on the surface roughness
mart felület
Milled
surface
Grinded
surface
köszörült
felület
edzett
réteg
vastagsága
[mm]
thicjness [mm]
layer
Hardened
polírozott
felület
Polished
surface
1.6
Anyag:
Material:CMo4
CMo4
P= 2000 W
1.2
0.8
0.4
400
500
600
700
[mm/min]
előtolásiFeed
sebesség
[mm/min]
The thickness of hardened layer as a function scanning rate
on steels with various surface roughness
Laser marking on steel surfaces
The local structural change as the basis of code formation
Depending on the applied energy density
various structural changes can be induced
(phase transformation, recrystallisation etc)