Laser Surface Processing and Model Studies

154 Pages·2013·5.663 MB·English

by  Bekir Sami Yilbas, Shahzada Zaman Shuja (auth.)

Materials Forming, Machining and Tribology
Bekir Sami Yilbas
Shahzada Zaman Shuja
Laser Surface
Processing and
Model Studies
Materials Forming, Machining and Tribology
Series Editor
J. Paulo Davim
For furthervolumes:
http://www.springer.com/series/11181
Bekir Sami Yilbas Shahzada Zaman Shuja
•
Laser Surface Processing
and Model Studies
123
BekirSami Yilbas
Shahzada ZamanShuja
Mechanical EngineeringDepartment
KingFahdUniversityof Petroleum and Minerals
Dhahran
SaudiArabia
ISSN 2195-0911 ISSN 2195-092X (electronic)
ISBN 978-3-642-36628-4 ISBN 978-3-642-36629-1 (eBook)
DOI 10.1007/978-3-642-36629-1
SpringerHeidelbergNewYorkDordrechtLondon
LibraryofCongressControlNumber:2013932463
(cid:2)Springer-VerlagBerlinHeidelberg2013
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Acknowledgment
We would like to acknowledge the role of King Fahd University of Petroleum
& Minerals in extending strong supportfrom the beginning to the end facilitating
every means during the preparation of this book. The authors wish to thank the
colleagues who contributed to the work presented in the book through previous
cooperation of the authors. In particular, thanks to Dr. Muammer Kalyon,
Dr. Nasser Al-Aqeeli, Dr. Saad Bin Mansoor, and all my graduate students.
v
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Conduction Heating of Solid Surfaces. . . . . . . . . . . . . . . . . . . . . . 5
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Analytical Treatment of Laser Pulse Heating . . . . . . . . . . . . . . 6
2.2.1 Exponential Pulse Heating. . . . . . . . . . . . . . . . . . . . . . 6
2.2.2 Laser Repetitive Pulse Heating. . . . . . . . . . . . . . . . . . . 11
2.3 Effect of Duty Cycle on Heating: Numerical Treatment. . . . . . . 13
2.4 Discussions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.4.1 Exponential Pulse Heating Case and Convection
Condition Resembling Assisting Gas at the Surface . . . . 16
2.4.2 Repetitive Pulse Heating Case and Convection
Condition Resembling Assisting Gas at the Surface . . . . 20
2.4.3 Effect of Duty Cycle on Heating and Convection
Condition Resembling Assisting Gas at the Surface . . . . 24
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3 Laser Melting of Solid Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.2 Analytical Treatment of Laser Melting Process. . . . . . . . . . . . . 30
3.2.1 The Closed Form Solution. . . . . . . . . . . . . . . . . . . . . . 30
3.2.2 Influence of Assisting Gas on the Melt
Layer Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.3 Numerical Treatment of Surface Melting . . . . . . . . . . . . . . . . . 34
3.3.1 Stationary Heating Source . . . . . . . . . . . . . . . . . . . . . . 34
3.3.2 Influence of Pulse Profile on Temperature Field. . . . . . . 39
3.3.3 Influence of Marangoni Flow on Temperature Field . . . . 41
3.3.4 Moving Heat Source Consideration. . . . . . . . . . . . . . . . 41
vii
viii Contents
3.4 Discussions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.4.1 Analytical Treatment of Laser Melting Process. . . . . . . . 43
3.4.2 Numerical Treatment of Laser Melting . . . . . . . . . . . . . 44
3.4.3 Influence of Pulse Profile and Marangoni Flow
on Temperature Field . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.4.4 Moving Heat Source Consideration. . . . . . . . . . . . . . . . 52
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4 Laser Melting of Two Layer Materials. . . . . . . . . . . . . . . . . . . . . 59
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.2 Numerical Treatment of Melting Process . . . . . . . . . . . . . . . . . 60
4.3 Discussions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.3.1 Laser Melting of Two-Layer Structure Influence
of Laser Pulse Repetition on Temperature
and Flow Field in the Melt Pool. . . . . . . . . . . . . . . . . . 63
4.3.2 Influence of Coating Material on Temperature
and Flow Field in the Melt Pool. . . . . . . . . . . . . . . . . . 69
4.3.3 Influence of Coating Material Thickness
on Temperature and Flow Field in the Melt Pool . . . . . . 75
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
5 Laser Induced Evaporation at the Surface . . . . . . . . . . . . . . . . . . 81
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.2 Analytical Treatment of Evaporation . . . . . . . . . . . . . . . . . . . . 82
5.3 Numerical Treatment of Evaporation. . . . . . . . . . . . . . . . . . . . 91
5.4 Numerical Solution of Governing Equations. . . . . . . . . . . . . . . 99
5.4.1 Phase Change Process. . . . . . . . . . . . . . . . . . . . . . . . . 100
5.4.2 Transiently Developing Vapor Jet. . . . . . . . . . . . . . . . . 100
5.5 Discussions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.5.1 Solution of Analytical Treatment of Evaporation . . . . . . 101
5.5.2 Predictions from Numerical Treatment
of Evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
6 Practical Applications of Laser Surface Treatment . . . . . . . . . . . . 111
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.2 Laser Shock Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
6.2.1 Heating, Recoil Pressure, and Wave Analysis. . . . . . . . . 113
6.2.2 Method of Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . 116
6.2.3 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
6.3 Laser Gas Assisted Nitriding. . . . . . . . . . . . . . . . . . . . . . . . . . 118
6.3.1 Thermal and Residual Stress Analysis. . . . . . . . . . . . . . 119
6.3.2 Experimental and Measurement of Young Modulus
and Fracture Toughness. . . . . . . . . . . . . . . . . . . . . . . . 121
Contents ix
6.4 Laser Surface Treatment of Pre-prepared Alloy. . . . . . . . . . . . . 123
6.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
6.5.1 Laser Shock Processing of Steel Surface . . . . . . . . . . . . 124
6.5.2 Laser Gas Assisted Nitriding of Steel Surfaces. . . . . . . . 127
6.5.3 Laser Surface Treatment of Pre-prepared Ti Alloy . . . . . 131
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
7 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
7.1 Analytical Treatment for Melting and Evaporation Processes . . . 139
7.2 Numerical Treatment for Melting and Evaporation Processes . . . 140
7.3 Practical Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
Chapter 1
Introduction
Abstract Lasers are widely used in surface engineering because of their advan-
tages over the conventional surface treatment methods. Some oftheseadvantages
include precision of operation, fast processing, and localized treatment. Laser
surface treatment involves with solid heating and phase change at the irradiated
surface.Inthischapter,theimportanceoflaserapplicationsinsurfaceengineering
is introduced and some aspects of laser surface treatment are presented.
Lasersarewidelyusedinsurfaceengineeringbecauseoftheiradvantagesoverthe
conventional surface treatment methods. Some of these advantages include pre-
cision of operation, fast processing, and localized treatment. Laser surface treat-
ment involves with solid heating and phase change at the irradiated surface. The
solid heating at the surface of the substrate material can be described through
introducing laser conduction limited heating situation; in which case, the
absorptionofirradiatedlaserenergyresultsinheatconductiononlyanditdoesnot
cause the phase change at the irradiated surface. When the laser beam interacts
with a solid surface, electrons in the irradiated region absorb the incident energy
and increase their excess energy in this region. This, in turn, results in thermal
separation of the electron sub-system from the lattice sub-system. Electrons and
lattice phonons thermally communicate to each other and electrons undergo sev-
eralcollisionswithlatticephononsthroughwhichsomeofelectronexcessenergy
transfers to lattice phonons. Since the number of collisions and electron excess
energy in the electron sub-system define the rate of energy transfer from the
electron sub-system to the lattice sub-system, the duration of electron excess
energy transfer becomes important for the type of energy transport in the solid
substrate, such as equilibrium or non-equilibrium transport. Thermal equilibrium
between electron and lattice sub-systems can be achieved when the interaction
time becomes on the order of the thermalization time of the substrate material;
therefore,forshortinteractiondurationsnon-equilibriumenergytransportgoverns
theheatingprocess.TheequilibriumbasedFourierheatinglawforheatconduction
is not applicable to describe the non-equilibrium energy transfer in a solid sub-
strate. In addition, the absorption depth of the incident radiation is small for
B.S.YilbasandS.Z.Shuja,LaserSurfaceProcessingandModelStudies, 1
MaterialsForming,MachiningandTribology,DOI:10.1007/978-3-642-36629-1_1,
(cid:2)Springer-VerlagBerlinHeidelberg2013
2 1 Introduction
metallic substrates and heat wave propagation at a finite speed takes place in the
irradiated region. The Fourier heating law fails to predict the correct temperature
rise in this region due to the consideration of infinite heat wave speed in the
irradiated solid. The phase lagging in energy transfer takes place in the solid
becauseoftheshortdurationofheatingandthesmallsizeoftheabsorptiondepth.
In such heating situations, model studies associated with thermal wave propaga-
tion, such as telegraph equation, or two-temperature model, or electron kinetic
theoryapproachesshouldbeincorporatedtodescribethetemperaturefieldduring
the thermal loading. In general, most of the laser treatment processes associated
with the surface engineering application are involved with the durations longer
than the thermalization time of the substrate material and the use of the Fourier
diffusion law becomes appropriate to describe the heating process.
Laser surface treatment of alloys provides dense layer with fine grains while
improving the hardness of the surface through the phase change and rapid solid-
ification in the surface region. Depending on the settings of laser output param-
eters,suchasthedutycycle,thepowerintensity,thelaserscanningspeed,andthe
materialproperties,thedepthofmeltpoolcanbecontrolled.Thisisnecessaryfor
the practical laser surface treatment applications. Controlling the heating param-
eters becomes crucial to achieve the desired melt zone during the treatment pro-
cess. Theexcessivelaser irradiated power orlow laser scanningspeedscan cause
evaporation at the surface, which increases the roughness of the treated surface
while limiting the practical applications of the treated surface. Therefore, laser
heating parameters should be selected properly in order to avoid poor quality of
thetreatedsurfaceandtheexcessiveoperationalcosts.Inordertoassessandselect
the proper levels of the laser surface treatment parameters, model studies of laser
heating process including phase change and molten flow inthe melt pool become
necessary. In addition, model studies give physical insight into the process and
provide usefulinformationontheinfluenceofmeltingparameters.Thenumerical
and analytical predictions reduce the experimental cost and minimize the exper-
imental time. In the case of irradiation of high intensity laser beams, the phase
change occurs in the irradiated region and the energy transfer in the irradiated
regioncanbeformulatedbyintroducinganon-conductionlimitedheatingprocess.
In this case, substrate materialunder goes solid heating, melting, and evaporation
during the heating process. The duration to reach melting and evaporation is
extremely short for the high power pulse heating operation. The rapid rise of
temperatureatthesurfacecausesdifficultiesinexperimentingaccuratelythelaser-
workpiece interactions. Consequently, model studies are easy to handle and give
insight into the laser-workpiece interaction mechanism particularly for high
intensity laser beams with short-pulse durations. During the irradiation pulse, the
laser irradiated power is absorbed in the skin of the substrate surface resulting in
volumetricheatsourceattheirradiatedregion.Althoughthedepthofabsorptionis
considerably shallow, it has a significant effect on the heat transport and the
internal energy gain of the substrate material in this region. Therefore, when
modelingtheheatingprocessinmetallicsubstrates,thevolumetricheatsourcedue
totheabsorptionoftheincidentradiationneedstobeaccountedintheanalysis.In