Ma e ials 2013, 6, 3963-3977; doi:10.3390/ma6093963
ma e ials
ISSN 1996-1944
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A icle
Mic os uc u al and Wea Beha io Cha ac e iza ion o
Po ous Laye s P oduced by Pulsed Lase I adia ion in
Glass-Ce amics Subs a es
Daniel Sola 1,*, Ana Conde 2, Iñaki Ga cía 2, Elena G acia-Escosa 2, Juan J. de Dambo enea 2
and Jose I. Peña 3
1 Ma e ials Physics Cen e , Uni e si y o Basque Coun y-CSIC, Pº Manuel La dizabal 5,
San Sebas ian 20.018, Spain
2 Depa men o Su ace Enginee ing, Co osion and Du abili y, Na ional Cen e o Me allu gical
Resea ch CENIM-CSIC, A . G ego io del Amo 8, Mad id 28.040, Spain;
E-Mails: [email p o ec ed] (A.C.); [email p o ec ed] (I.G.);
[email p o ec ed] (E.G.-E.); [email p o ec ed] (J.J.D.)
3 Depa men o Science and Technology o Ma e ials and Fluids, Ma e ial Science Ins i u e o
A agon, Uni e si y o Za agoza-CSIC, Ma ia de Luna 3, Za agoza 50.018, Spain;
E-Mail: [email p o ec ed]
* Au ho o whom co espondence should be add essed; E-Mail: [email p o ec ed];
Tel.: +34-946-014-051; Fax: +34-946-014-178.
Recei ed: 1 July 2013; in e ised o m: 21 Augus 2013 / Accep ed: 4 Sep embe 2013 /
Published: 9 Sep embe 2013
Abs ac : In his wo k, wea beha io and mic os uc u al cha ac e iza ion o po ous
laye s p oduced in glass-ce amic subs a es by pulsed lase i adia ion in he nanosecond
ange a e s udied unde unidi ec ional sliding condi ions agains AISI316 and co undum
coun e bodies. Depending on he op ical con igu a ion o he lase beam and on he
wo king pa ame e s, he local empe a u e and p essu e applied o e he in e ac ion zone
can gene a e a po ous glass-ce amic laye . Ma e ial ans e ence om he ball o he po ous
glass-ce amic laye was obse ed in he wea es s ca ied ou agains he AISI316 ball
coun e ace whe eas, in he case o he co undum ball, he wea olume loss was
concen a ed in he po ous laye . Wea a e and ic ion coe icien p esen ed highe alues
han expec ed o dense glass-ce amics.
Keywo ds: pulsed lase i adia ion; laye s; wea esis ance; glass-ce amic
OPEN ACCESS
Ma e ials 2013, 6 3964
1. In oduc ion
Lase p ocessing has been inco po a ed in indus y o e he las decades being o g ea in e es in he
ield o op ics, elec onics, mic oelec onics, ae ospace and medicine. Se e al me hods o p ocessing,
such as lase machining, mic omachining, ma king, d illing and pulsed lase deposi ion ha e
been de eloped [1,2]. Lase echniques a e cos -e ec i e compa ed o o he adi ional su ace
modi ica ion me hods and i may be applied o a wide ange o subs a es, such as me als, ce amics and
semiconduc o s [3]. Reduc ion in p oduc ion cos s, s a and main enance sa ings as well as in ool
wea ing, make lase p ocessing he mos sui able wo king ool o machining ha d and b i le ma e ials.
The appea ance o echniques o gene a ing sho and ul asho lase pulses, anging om ens o
nanoseconds o a ew em oseconds, ha e allowed he a ailabili y o mo e powe ul sys ems, wi h
powe densi ies ha can each e awa s/cm2. These lase sys ems, wi h be e ea u es and lowe
p ices, o e a high-speed/high-quali y ool o lase machining, which is o g ea in e es in bo h basic
and applied esea ch [3,4]. Lase abla ion depends on lase wa eleng h, op ical ea u es o lase beam,
pulsewid h ange, machining me hod and on he op ical- he mal-mechanical p ope ies o he subs a e
o be p ocessed [5]. Some heo e ical desc ip ions ha e been de eloped by many au ho s o gene alize
he s ages o he abla ion p ocess: lase adia ion abso p ion, hea ans e o he a ge , e apo a ion and
gas-dynamic o he apo [6–13].
Glass and glass-ce amic subs a es a e commonly used in a a ie y o applica ions such as lasing
sys ems, op o-in o ma ic de ices, mic o-op ical componen s, mi o s and wa eguides [14–19]. In
pa icula , glass-ce amic subs a es p esen a g ea in e es o indus ial and enginee ing applica ions
due o hei ad an ages wi h espec o o he ce amic and glassy ma e ials because o hei good
chemical ine ness, high empe a u e s abili y and glass ansi ion empe a u e, low coe icien o linea
expansion, excellen he mal shock esis ance and supe io mechanical p ope ies such as ab asion,
impac , e c. Fu he mo e, lase machining and su ace modi ica ion o hese ma e ials a e e y
in e es ing o unc ional pu poses in indus ial applica ions since hese modi ica ions may be applied
as he mal-ba ie s, hea -conduc o acks, inclusion o he mal senso s, e c. [20–23].
In p e ious wo ks, he o ma ion mechanisms o gene a ing po ous laye s by pulsed lase
i adia ion on he su ace o a glass-ce amic subs a e in unc ion o he lase wa eleng h and subs a e
empe a u e in he nanosecond ange we e s udied [22,23]. In his wo k we p esen he wea beha io
cha ac e iza ion o his po ous laye in o de o de e mine he ic ion coe icien (COF) and he wea
esis ance. This knowledge will allow us o compa e he ibological beha io in u u e wo ks since
nex s ages will be o imp o e he wea esis ance by educing he po osi y by means o con olling he
a mosphe e in which he p ocess is ca ied ou , by a lase cladding ea men on he su ace o by
injec ing Al2O3 o Z O2 powde s in o he laye du ing he lase p ocessing.
2. Expe imen al
2.1. Lase P ocessing
A comme cial diode-pumped Q-Swi ch Nd:YVO4 lase sys em (T uMa k 6230, T ump ) has been
used o p oduce he po ous laye . This sys em ope a es a a wa eleng h o 532 nm, Gaussian mode
TEM00 wi h a beam quali y ac o M2 < 1.2 and a mean powe o 7.2 wa s. The lase sys em is
Ma e ials 2013, 6 3965
equipped wi h a p og ammable gal anome e a he ou pu o he ca i y con olled by CAD so wa e.
In his way, he beam can be de lec ed making a bidi ec ional mo emen in such a way ha any
p ede ined pa e n and p ocessing p ocedu e can be pe o med. The machining p ocess is con olled by
he diodes pump cu en IP (in ela ion o peak powe ), pulse equency , scanning speed V and
dis ance be ween adjacen lines Δ. The sys em inco po a es a con ex lens wi h ocal leng h F o 160 mm.
Thus, using he equa ions [3]:
0
2
π
λ4
D
FM
Dbw
(1)
λ4
π
2
2
M
D
Rbw
(2)
whe e D0 is he diame e o he lase beam be o e he op ical lens, he diame e a he ocal poin Dbw
and he Rayleigh ange R o his sys em a e, app oxima ely, 12 μm and 177 μm espec i ely.
As ma e ial, a glass-ce amic subs a e, Ce an Sup ema®, manu ac u ed by Scho was used. Thei
chemical composi ion and s uc u e we e ully cha ac e ized by he au ho s in a p e ious pape [23].
I s main p ope ies a e shown in Table 1.
Table 1. P ope ies o he glass-ce amic subs a e Ce an Sup ema®.
P ope y
Value
Uni
Densi y
2.5 *
g/cm3
Bending s eng h
110 *
MPa
Knoop Ha dness
600 *
–
The mal conduc i i y
1.7 *
W/mK
The mal di usi i y
0.85 #
m2/s × 10−6
Mel ing empe a u e
1300 *
K
* Scho Technical Da a; # Measu e ca ied ou a he Ins i u e o Ce amics and Glass.
The sample was placed a ocal dis ance and p ocessed a oom empe a u e. The lase p ocessing
was pe o med wi h lase pulses o 0.27 mJ, an i adiance o 28 GW/cm2, using a wo king equency
o 20 kHz, a scanning speed o 25 mm/s and a dis ance be ween adjacen lines o 10 μm.
2.2. Cha ac e iza ion Techniques
Mo phology and composi ion ha e been de e mined by means o scanning elec on mic oscopy
(SEM) using a JEOL JSM6400 wi h EDX analysis. Pho og aphy has been ca ied ou wi h a
s e eoscope mic oscope.
C i ical load and ha dness we e measu ed by a Vicke s Zwick ha dness es e using loads be ween
0.1 and 5 kg .
Unidi ec ional sliding wea es s we e conduc ed using a Mic o es ibome e wi h a ball-on-disk
con igu a ion. The ibological pai was o med by he po ous glass-ce amic sample and s ainless s eel
(AIS316) o co undum balls (Al2O3) o 6 and 3 mm diame e , espec i ely. The no mal loads applied
anged om 1 N o 3 N, he con ac equency was 8 Hz, he diame e o he wea ack 4 mm and he
sliding dis ance a ied be ween 50 m and 500 m depending on he load and coun e body used in each
Ma e ials 2013, 6 3966
es . Wea es s we e pe o med a oom empe a u e in he a mosphe e o he labo a o y. Table 2
ga he s wea es condi ions used.
Table 2. Wea es s condi ions.
Tes Pa ame e s
Tes s 1
Tes s 2
Ball ma e ial/diame e , mm
AISI 316/6 mm
Al2O3/3mm
Wea ack diame e , mm
4
4
F equency, pm/Hz
480/8
480/8
Sliding speed, m/s
0.1
0.1
Load, N
3
1
2
1
Sliding dis ance, m
500
200
50
100
Roughness measu emen s and wea acks p o ile we e measu ed by means o Su ace Analyze
178–821 (Su es 401) om Mi u oyo. F om ou p o iles measu ed o each wea ack, olume loss
was calcula ed mul iplying he a e age p o ile a ea by he leng h o he ci cula wea ack.
3. Resul s and Discussion
3.1. Laye Fo ma ion Mechanisms
The possibili y o p oducing po ous laye s on he su ace o glass-ce amic subs a es has been
demons a ed when he subs a e is machined by means o pulsed lase s in he nanosecond ange [22,23].
Lase abla ion in he nanosecond ange is a pho o he mal-mechanical p ocess so ha he ma e ial is
emo ed by he he mal mechanisms ac i a ed by he lase beam. They essen ially consis o he
abso p ion o he lase ene gy and subsequen e apo a ion and ejec ion o he ma e ial. Du ing
he abla ion p ocess, a hin laye o ma e ial in liquid-phase is o med in he in e ac ion zone [2],
Figu e 1a. The ecoil p essu e p oduced in he p ocess squeezes he liquid ou om he in e ac ion
zone and he ma e ial is emo ed om he su ace ia e apo a ion and liquid-phase expulsion. The
hickness o liquid phase, hl, and ecoil p essu e, P ec, can be exp essed as [2]:
4/1
2/1
)(
a
V
lI
H
Dh
(3)
a
IP 5
ec 10
(4)
whe e D is he he mal di usi i y, ΔH he en halpy o apo iza ion, and Ia he abso bed lase in ensi y.
Since he a ia ions o he mal di usi i y and en halpy o apo iza ion wi h empe a u e a e
negligible [24,25], he hickness o he mol en laye and he ecoil p essu e depend mainly on he
abso bed i adiance.
The o ma ion mechanisms di e depending on he lase wa eleng h used. When he lase
wa eleng h is in he nea in a ed ange (NIR) he laye o ma ion depends on he subs a e
empe a u e. A oom empe a u e o o empe a u es lowe han 300 °C he lase p ocessing gene a es
a g oo e on he su ace. Ne e heless, by inc easing he subs a e empe a u e, he ib a ions o he
ions in he la ice also inc ease. Taking in o accoun ha he mel ing empe a u e o he glass-ce amic
is abou 1300 °C, as empe a u e inc eases he ma e ial acqui es a pseudo-plas ic cha ac e . This
Ma e ials 2013, 6 3967
beha io oge he wi h he ac ha he abla ed pa icles ejec ed om he in e ac ion zone shield he
incoming i adia ion p oduce a diminu ion in he e ec i e i adiance and he e o e in he ecoil
p essu e, esul ing in an inc ease o he hickness o he laye in liquid-phase p esen in he in e ac ion
zone, Figu e 1b. The p essu e exe ed by he pulsed lase beam on o he mol en in e ac ion zone
p oduces an ai bubble gene a ion inside he laye which leads, a e cooling, o he gene a ion o he
po ous laye . Figu e 2a,b shows he on al and c oss-sec ion iew o he laye ob ained by p ocessing
a 600 °C. In his case, he po ous laye can only be p oduced a low scanning speeds, 1 mm/s.
Figu e 1. Scheme o abla ion p ocess and mol en laye o hickness hl o med in he
in e ac ion zone a oom empe a u e T1 (a) and a high empe a u e T2 (b). The hickness
inc eases when he su ace empe a u e o he glass-ce amic subs a e is hea ed.
The o ma ion o he po ous laye is also possible when he lase wa eleng h is in he g een o in
he UV ange. In his case, he o ma ion mechanisms a e in ela ion wi h he a ia ion o he
abso bance o he glass-ce amic subs a e wi h he wa eleng h. The abso bance o he glass-ce amics
subs a e dec eases wi h he wa eleng h [23]. In pa icula , he op ical abso p ion coe icien s, α, o
355 and 532 nm a e 62.13 and 28.37 cm−1, 17 and 8 imes g ea e han o 1064 nm, he alue o which
is 3.52 cm−1. As he abso p ion coe icien inc eases he abso bed i adiance Ia and he abso bed powe
pe uni o olume (1 − R)·α·Ia a e highe . Since he alues o di use e lec ion R o 1064, 532 and
355 nm a e 0.94, 0.96 and 0.87 [23], his powe densi y is abou 17.52, 31.77 and 68.67 GW/cm3
espec i ely. Acco ding o he Equa ions (3) and (4), when he subs a e p ocessing is ca ied ou wi h
a sho e wa eleng h he p essu e inc eases and a diminu ion in he hickness o he laye in
liquid-phase is p oduced. Fu he mo e, he su ace empe a u e can be exp essed as [6]:
2/1
)(2 TT Lmn
(5)
whe e
kDIT Lam /))(( 2/1
,
L
is he pulse wid h, he wo king equency, D he he mal di usi i y
and k he he mal conduc i i y.
Thus, an inc ease in he abso bed i adiance p oduces a highe subs a e empe a u e on he
su ace,
n
T
. In his way, lase p ocessing a 532 nm o 355 nm p oduces a local inc ease in he
empe a u e o he subs a e and in he ecoil p essu e exe ed o e he subs a e, inducing a g ow h o
Ma e ials 2013, 6 3968
he c ys alline phase o he glass-ce amic subs a e and gene a ing he po ous laye . Mo eo e , he
inc ease in he abso p ion coe icien allows p oducing he po ous laye a highe scanning speeds,
25 and 60 mm/s o 532 and 355 nm espec i ely. Fu he mo e, he po ous laye can be p oduced a
oom empe a u e, wi hou he d awback o hea ing he whole sample, and wi h lowe ene ge ic cos ,
since he ene gy deli e ed in he p ocess, calcula ed by means o he pulse ene gy, equency, scanning
speed and dis ance be ween adjacen lines, a e 29.4, 0.86 and 0.42 J/mm2 o 1064, 532 and 355 nm
espec i ely. Al hough lase ea men may cause a build-up o s ess in he adjacen egions [26] he
ea u es o his lase p ocessing and he po ous na u e o he laye elease he possible s esses
p oduced while he p ocess is ca ied ou , as shown in p e ious wo ks by means o Raman
spec oscopy and mechanical es s [20,27].
Figu e 3 shows he op iew (a) and c oss-sec ion mic og aph (b) o he po ous laye ob ained by
using a lase sys em emi ing a 532 nm. As seen in Figu e 3a he laye p esen s a ex u e in he
scanning di ec ion p oduced by he local hea ing induced by he lase beam. As Figu e 3b depic s, he
hickness is a ound 150 μm and p esen s high po osi y.
Figu e 2. Top iew (a) and c oss-sec ion iew (b) o he po ous laye gene a ed a 600 °C
wi h a lase sys em emi ing a 1064 nm.
Figu e 3. Top iew (a) and c oss-sec ion mic og aph (b) o he po ous coa ing p oduced
wi h a lase sys em emi ing a 532 nm.
Ma e ials 2013, 6 3969
In his wo k, he aim is o in es iga e he wea esis ance o he laye . Fo his pu pose, he po ous
laye was p oduced by means o a pulsed lase sys em emi ing a 532 nm since he hickness o he
laye p oduced a a wa eleng h o 355 nm was oo hin o assess he wea beha io , and he scanning
speed equi ed o p oducing he coa ing a a wa eleng h o 1064 nm was oo slow and en ails he
hea ing o he whole sample beyond 300 °C .
3.2. Composi ional and Mic os uc u al Cha ac e iza ion
The chemical composi ion o he laye was analyzed by semi-quan i a i e EDX mic oanalysis,
concluding ha he composi ion o he po ous laye was he same as he glass-ce amic o me and
consis ed mainly o SiO2, Al2O3, ZnO, MgO and TiO2, Table 3, i s column. Fu he mo e a XRD
analysis ca ied ou on a lase ea ed sample and compa ed o he glass-ce amic subs a e showed ha
he laye was also glass-ce amic. In bo h cases he c ys alline phase was he same, c ys als o
MgAl2Si4O12, he size o which was a ound 36 and 42 nm [23].
Table 3. EDX Composi ion o he po ous laye be o e and a e wea ing es s ca ied ou
wi h AISI316 and Al2O3 balls.
a . %
Po ous Laye
Wo n Laye agains AISI316
Wo n Laye agains Al2O3
O
72.10
69.16
72.17
Mg
0.51
0.50
0.53
Al
6.15
5.74
6.96
Si
19.63
16.15
16.45
Zn
1.33
0.20
0.48
Ti
0.31
0.71
0.41
C
–
1.15
–
Fe
–
6.21
–
3.3. T ibological Beha iou
P io o he wea es s, he ha dness o he po ous laye was measu ed o es ima e he maximum
load ha he laye may wi hs and wi hou c acking du ing he wea es . Al hough he nominal
ha dness o he glass-ce amic Ce an Sup ema is 5.56 GPa, due o he po ous s uc u e o he laye ,
loads abo e 0.4 kg on he Vicke s inden e induce c acking o he laye . The e o e he ha dness o he
po ous laye is ema kably lowe han he dense subs a e being he ha dness measu ed applying a load
o 5 kg only 1.33 GPa. The e o e, he maximum load ha can be applied wi hou se e e c acking o
wea es is 4 N (0.4 kg ).
Wea beha io was ini ially es ed agains AISI316 a wo loads, 1 and 3 N. The lowe load applies
a He z ini ial medium p essu e o 0.22 GPa and a maximum p essu e o 0.33 GPa, while a load o 3 N
applies an he zian a medium p essu e o 0.32 GPa and a maximum p essu e o 0.48 GPa. In all cases
p essu e is below ei he he measu ed ha dness o he laye o he load limi o c acking. Figu e 4
shows he a ia ion o he ic ion coe icien , COF, wi h he load. A he lowe load, he COF is as
high as 1.7 meanwhile a 3 N he COF educes o 1.1–1.2. In bo h cases such COF is no ably highe
han he alues epo ed in he li e a u e o di e en ypes o dense glass-ce amic ma e ials, which is
a ound 0.8 o a wide ange o loads and coun e bodies [28–30].
Ma e ials 2013, 6 3970
Figu e 4. F ic ion coe icien , COF, eco ded du ing he wea es s agains AISI316 ball a
1 and 3 N o no mal load wi h 200 and 500 m o sliding dis ance, espec i ely.
The analysis o he wo n su aces e ealed ha he s eel ball appea s no ably e oded, Figu e 5,
meanwhile he wea acks on he glass-ce amic acqui e an o ange-like colo , Figu e 6, indica ing ha
oxide ans e ence om he ball o he po ous laye has been p oduced. The analysis o he wea ack
pe o med by EDX, con i med ha such ma e ial ans e ence occu ed be ween he glass-ce amic
laye and he AISI316 ball. Table 3 compa es he chemical composi ion o he po ous glass-ce amic
laye be o e and a e he wea es s. Simila ly Table 4 compa es he chemical composi ion o he ball
be o e and a e he same wea es a he di e en loca ions iden i ied in Figu e 5. While he wea
ack shows he p esence o C and Fe, coming om he s eel ball, he analysis o he la ened a ea o
he ball shows he p esence o Al, Mg, and Si oxides coming om he glass-ce amic ma e ial.
Figu e 5. Appea ance o he wo n su ace o he AISI 316 ball showing he a eas in which
he EDX analyses we e ca ied ou (see Table 3).
050 100 150 200 250 300 350 400 450 500
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Load : 3N
Load : 1N
COF
Sliding dis ance (m)
Ma e ials 2013, 6 3971
Figu e 6. Appea ance and p o ile o he wea ack in a glass-ce amic sample a e wea
es agains AISI 316 ball wi h a no mal load o 3 N and sliding dis ance o 500 m.
The ball exhibi s a se e e ab asion by he ha d ce amic oxide pa icles and consequen ly he con ac
a ea has inc eased ema kably du ing he es . Al hough he wea ack wid h is e y la ge (a ound
1.5 mm) he a e age dep h is only 50 μm, Figu e 6. This ac indica es ha mos o he wo n olume is
concen a ed on he AISI316 ball and he appa en wid h o he wea ack is mainly due o he
widening o he ball con ac a ea mo e han a eal se e e wea o he po ous ce amic laye .
In o de o educe he se e i y o he es s o he s eel used as a coun e body, u he es s we e
pe o med a a lowe load and sho e sliding dis ance, 1 N and 100 m espec i ely. In hese new
condi ions he glass-ce amic ma e ial did no show any measu able olume loss since he wea ack is
ha dly dis inguished con e sely o wha occu ed in he s eel ball whe e se e e ma e ial loss and a
wide la ened a ea is s ill obse ed.
Table 4. Composi ion o he AISI316 ball la ened su ace in con ac wi h he coa ing
a e he wea ing es . The analyses we e pe o med in he a eas poin ed ou in he inse o
Figu e 5b.
a .%
AISI316
Wo n AISI316 Ball
Ball
1
2
O
–
7.85
52.74
Mg
–
0.03
0.31
Al
–
0.06
2.75
Si
–
1.70
7.51
Ti
–
–
0.12
C
14.16
11.41
4.06
Fe
85.24
64.97
21.35
Ni
0.49
–
–
In sigh o he esul s ob ained om he wea es s ca ied ou using he AISI316 ball, a new ba ch o
es s we e pe o med using a much ha de coun e body, namely a co undum ball o 3 mm diame e .
The e o e he ic ion coe icien o he po ous laye agains co undum was de e mined o a load o
0.0 0.5 1.0 1.5 2.0 2.5
-50
-40
-30
-20
-10
0
10
20
30
40
50
dep h m)
wid h(mm)
3N, 500m
