Laser beam hardening is a process that uses a high-energy laser beam to heat and harden the surface of a metal part. It offers advantages over traditional hardening methods like being a localized process that only hardens the surface. Key steps include pre-treating and cleaning the surface, masking off non-hardening areas, scanning the laser beam over the surface to heat and harden it, rapidly quenching the surface, and performing quality control checks on the hardened layer. Process parameters like laser power, beam size and speed, and quenching method affect the hardness and properties of the hardened surface. A variety of steel, aluminum, and titanium alloys can be suitable for laser beam hardening.

1. Laser Beam Hardening
Presented By:
ASHISH CHAURASIYA(214122007)
SUROJ SINGH(214122029)
SHANTANU SINGH(214122027)
Heat Treatment (PR613)
M. Tech, 2nd Semester, Jan-2023
Manufacturing Technology
Department of Production Engineering
National Institute of Technology Tiruchirappalli,
Tamil Nadu - 620015

2. INTRODUCTION
• Laser surface hardening is a manufacturing process that uses a high-energy laser beam to
heat and harden the surface of a metal part. The process involves directing the laser beam at
the surface of the part, which causes the surface temperature to rapidly rise and then cool
down quickly, creating a hardened surface layer.
• The main advantage of laser surface hardening over traditional hardening methods, such as
heat treating, is that it is a localized process that only affects the surface layer of the part.
This means that the bulk of the part remains relatively unaffected, which can help to
minimize distortion, cracking.
• used in the automotive, aerospace, and toolmaking industries, where high levels of wear
resistance and durability are required. The process can be used on a wide range of metals,
including steel, aluminum, titanium, and other alloys.

3. HISTORY
• The history of laser-based hardening techniques can be traced back to the 1960s. At that
time, laser technology was still in its infancy, and researchers were just beginning to explore
the potential applications of lasers in manufacturing processes.
• In the early 1960s, researchers at the Max Planck Institute for Metals Research in Germany
were the first to investigate the use of lasers for surface hardening. They used a ruby laser to
heat and harden the surface of steel parts, and found that the process produced a significant
improvement in the wear resistance of the material.
• Over the next few decades, laser technology continued to advance, and researchers around
the world began to explore the use of different types of lasers for surface hardening
applications. By the 1990s, laser surface hardening had become an established process in
many industries, including automotive, aerospace, and toolmaking.

4. WHY LASER?
• Laser surface hardening offers several advantages over traditional hardening methods,
which is why it is widely used in many industries. Here are some of the main reasons
why lasers are used for surface hardening:
1.Localized process: Laser surface hardening is a localized process that only affects the
surface layer of the part, leaving the bulk of the part relatively unaffected. This can help
to minimize distortion, cracking, and other problems that can arise from traditional
hardening methods.
2.Precision: Laser surface hardening is a highly precise process that can be controlled to
very tight tolerances. This makes it ideal for applications where high levels of precision
and consistency are required.
3.Speed: Laser surface hardening is a fast process that can be completed in a matter of
seconds or minutes. This can help to increase production throughput and reduce lead
times.

5. CONT…..
5.Versatility: Laser surface hardening can be used on a wide range of metals, including steel,
aluminum, titanium, and other alloys. This makes it a versatile process that can be applied to
many different manufacturing applications.
6.Quality: Laser surface hardening produces a high-quality, uniform surface layer that is
resistant to wear and other forms of damage. This can help to increase the overall durability
and lifespan of the part.
• Overall, laser surface hardening is a highly effective and efficient process that offers many
benefits over traditional hardening methods, making it an ideal choice for many
manufacturing applications.

6. FUNDAMENTALS OF LASER
• The word "laser" is stands for Light Amplification by Stimulated Emission of Radiation.
• The light emitted from a laser is monochromatic. In contrast, ordinary white light is a
combination of many colors (or wavelengths) of light.
• Lasers emit light that is highly directional, that is, laser light is emitted as a relatively
narrow beam in a specific direction. Ordinary light, such as from a light bulb, is emitted
in many directions away from the source.
• The light from a laser is said to be coherent, which means that the wavelengths of the
laser light are in phase in space and time. Ordinary light can be a mixture of many
wavelengths.
• These three properties of laser light can make it unique than ordinary light.

7. CHARACTERISTICS OF LASER
Monochromaticity
• Energy of a photon E = hc/λ,(h - Planck's constant, c- speed
of light, λ
- wavelength).
• Laser emits all photons with the same energy, and thus the
same wavelength.
Coherence
• Emitted photons have a definite phase relationship with each
other.
7

8. 8
Directionality and beam divergence
• Perfectly placed opposing mirrors enable multiple reflections of photons and produce a
well-collimated beam with high directionality and low divergence.
• Nd:YAG (l = 1.06 µm with 3mm diameter)- Divergence angle 0.02014°.
• Many wavelengths Monochromatic
• Multidirectional Directional
• Incoherent coherent
CHARACTERISTICS OF LASER

9. 9
LASING ACTION
• Energy is applied to a medium raising electrons to an unstable energy level.
• These atoms spontaneously decay to a relatively long- lived, lower energy, metastable
state.
• A population inversion is achieved when the majority of atoms have reached this
metastable state.
• Lasing action occurs when an electron with stimulated emission returns to its
ground state and produces a photon.

10. LASING ACTION DIAGRAM
Energy
Introductio
n
Ground State
10
Excited State
Metastable State
Spontaneous
Energy Emission
Stimulated
Emission of
Radiation

11. COMPONENTS OF A LASER
• Lasing material (crystal, gas, semiconductor, dye, etc...)
• Pump source (adds energy to the lasing material , e.g. flash lamp, electrical
current to cause electron collisions, radiation from a laser, etc.)
• Optical cavity (Optical resonator) consisting of reflectors to act as the feedback
mechanism for light amplification.
11

12. Modes of operation
• A laser can be classified as operating in either continuous or pulsed mode,
depending on whether the power output is essentially continuous over time or
whether its output takes the form of pulses of light.
Energy
(Watts)
Time Energy
(Watts)
Time
12

13. 13
CONTINUOUS WAVE OPERATION
• Laser beam whose output power is constant over time.
• Many types of lasers can be made to operate in
continuous wave mode to satisfy such an application.
PULSED OPERATION
• Pulsed operation of lasers refers to any laser not classified
as continuous wave, so that the optical power appears in
pulses of some duration at some repetition rate.

14. 14
SOLID-STATE LASERS
• Solid-state lasers use a crystalline or glass rod which is "doped" with ions that provide
the required energy states.
• The population inversion is actually maintained in the "dopant", such as chromium
or neodymium.
• These materials are pumped optically using a shorter wavelength than the lasing
wavelength, often from a flashtube or from another laser.
• Neodymium is a common "dopant" in various solid-state laser crystals, including
yttrium orthovanadate (Nd:YVO4), yttrium lithium fluoride (Nd:YLF) and yttrium
aluminium garnet (Nd:YAG).
TYPES OF LASERS

15. Nd:YAG Laser
• It is a solid state laser
• It is having four laser level
• Light energy produced by Xenon/Krypton flash tube used as a pumping source.
• Dimension of rod: 10 cm long and 6 to 9 cm in diameter.
• Wavelength is 1064nm,laser can be continuous or pulsed .
• for steel depth from 0.1 to 1.5 mm, depending on the parameters.

16. 16
GAS LASERS
• Gas lasers consist of a gas filled tube placed in the laser cavity .
• Avoltage (the external pump source) is applied to the tube to excite the atoms in the gas
to a population inversion.
• The light emitted from this type of laser is normally continuous wave (CW).
• Large gas lasers known as gas dynamic lasers use a combustion chamber and
supersonic nozzle for population inversion.

17. CO2 LASER:
• In carbon dioxide laser, Co2 gas molecules are used as the active medium and
population inversion is achieved by the electrical pumping method.
• The active medium is a gas mixture of CO2, N2 and He. The laser transition takes place
between the vibrational states of CO2 molecules.
• it consists of a tube 5m long and 2 cm in diameter. The discharge is produced by d.c
excitation. The resonant cavity is formed of confocal silicon mirrors
• Co2 and N2 in the ratio of about 0.8:1, N2 molecule help in achieving the population
inversion and wavelength is 10.6 µm

18. Laser beam hardening process
1.Material Preparation: The material to be hardened is first prepared by
cleaning and removing any surface contaminants, such as oil or grease.
2.Masking: Areas of the material that should not be hardened are masked off
using a protective coating or material.
3.Laser Beam Pre-Treatment: The laser beam is directed at the surface of the
material to be hardened. This pre-treatment step is used to remove any
surface oxide layers or coatings, and to promote better absorption of the laser
energy.
4. Laser Beam Hardening: The laser beam is directed at the surface of the
material, with the beam parameters (such as power, duration, and focus) set to
achieve the desired depth and hardness of the surface layer.

19. 5.Quenching: Immediately after the laser beam hardening step, the surface
of the material is rapidly cooled using a quenching medium such as water,
oil, or air. This step is crucial to ensure the desired metallurgical properties
of the hardened layer.
6.Post-Processing: The hardened material is then subjected to post-
processing steps such as cleaning, grinding, or machining, to achieve the
desired final dimensions and surface finish.
7.Quality Control: The final product is inspected to ensure that it meets the
desired specifications for hardness, depth, and metallurgical properties.
It is important to note that the specific process flow chart for laser beam
hardening can vary depending on the material being hardened, the desired
properties of the hardened surface, and the type of laser being used.

20. Surface preparation
• The surface of the material must be clean and free from contaminants such as oil,
grease, rust, and scale to ensure optimal hardening results.
1. Cleaning: The material surface is cleaned using a variety of methods such as
solvent cleaning, alkaline cleaning, acid pickling, or sandblasting. This removes
any dirt, oil, rust, or other contaminants that may interfere with the laser
hardening process.
2. Preheating: Preheating the material surface before laser hardening can help to
reduce thermal shock and minimize the risk of distortion or cracking. The
preheating temperature and time depend on the material type and thickness.
3. Masking: In some cases, certain areas of the material surface may need to be
protected from the laser beam, such as areas that require further machining or
assembly. Masking can be done using various materials such as tape, paint, or
ceramic coatings.
4. Surface Roughening: Roughening the material surface can improve the
adhesion of the hardened layer and help to prevent spalling or delamination.
This can be done using various methods such as shot peening or abrasive
blasting.

21. MASKING
• Masking is typically used in laser hardening when only specific areas of the material
surface need to be hardened. For example, if a part has multiple features, such as
holes or grooves, that do not require hardening, masking can be used to protect those
areas while the surrounding areas are hardened.
• Masking can also be used when subsequent machining or assembly operations are
required. By masking off certain areas, the material can be hardened without affecting
the dimensions or properties of those areas, which may be critical for the part's
functionality.
• Another scenario where masking is used is when different sections of a single part
require different hardening depths. By masking off the areas that do not require
hardening or require a different hardening depth, the process can be customized for
different sections of the same part.
Masking types are-
1. Tape masking
2. Paint masking
3. Ceramic coating

22. LASER BEAM PRE-TREATMENT
• Laser-based pre-treatment is a surface preparation technique that uses a laser to modify
the surface properties of a material before a subsequent surface treatment process. Laser
pre-treatment can improve the adhesion
1.Laser Cleaning: Laser cleaning involves the use of a laser to remove surface
contaminants such as oil, grease, and rust. This method can effectively clean the surface
without damaging the substrate and can be used for both metallic and non-metallic
materials.
2.Laser Surface Texturing: Laser surface texturing involves the use of a laser to create
micro- or nano-scale features on the material surface. These features can improve the
surface roughness, which can enhance the adhesion of subsequent coatings or hardening
layers.
• The advantages of laser-based pre-treatment over traditional pre-treatment methods,
such as chemical etching or mechanical abrasion, include precision, flexibility, and
environmental friendliness. Laser pre-treatment can be customized for different materials,
surface conditions, and treatment requirements, providing a high level of control and
reproducibility. Additionally, laser pre-treatment does not generate hazardous waste or
require the use of chemicals or solvents, making it a cleaner and safer alternative.

23. POST PROCESSING
• Post-processing of laser beam hardened material can be done to improve the final
properties and performance of the hardened layer. Some of the common post-processing
techniques include:
1.Tempering: After the material has been hardened, it can be subjected to a tempering
process to reduce the internal stress and improve the toughness and ductility of the
material. This process involves reheating the material to a specific temperature for a
certain duration, followed by controlled cooling.
2.Shot Peening: This process involves bombarding the hardened surface with small metallic
or ceramic particles at high velocities. This can help to further increase the surface
hardness and compressive residual stress, improving the material's resistance to fatigue
and stress corrosion cracking.
3.Grinding and Polishing: These processes can be used to remove any surface
irregularities and improve the surface finish of the hardened layer. This can also improve
the material's resistance to wear and improve its aesthetic appearance.
4.Machining: If the hardened layer needs to be machined for final dimensional accuracy or
functional requirements, special tooling and techniques may be required to overcome the
increased surface hardness.

24. QUALITY CONTROL
• Quality control is an important aspect of laser beam hardening to ensure that the
hardened material meets the desired requirements and specifications. Some of
the common quality control measures used in laser beam hardening include:
1.Hardness testing: This involves measuring the hardness of the hardened layer
using techniques such as Rockwell, Vickers, or Brinell hardness testing. This can
ensure that the material has achieved the desired hardness and depth of
hardening.
2.Microstructure analysis: This involves examining the microstructure of the
hardened layer using techniques such as metallography or scanning electron
microscopy (SEM). This can help to ensure that the material has undergone the
desired phase transformation and has the desired microstructure for the intended
application.
3.Surface finish analysis: This involves measuring the surface roughness and other
surface characteristics of the hardened layer using techniques such as
profilometry or optical microscopy. This can ensure that the surface finish meets

26. Parameters involve in LBH
1.Laser Power: The laser power determines the amount of energy delivered
to the material, which affects the depth and hardness of the hardened
layer.
2.Beam Size and Focus: The beam size and focus affect the area of the
material being treated, and the intensity of the laser energy delivered to
the surface.
3.Scanning Speed: The scanning speed of the laser beam across the
surface affects the duration of the energy exposure and the resulting depth
and hardness of the hardened layer.
4.Pulse Duration: The pulse duration of the laser beam affects the heating
and cooling rates of the material, which can affect the final metallurgical
properties of the hardened layer.

27. 5.Laser Beam Delivery: The way the laser beam is delivered to the material
can also affect the hardening process. For example, some systems use a
stationary laser beam, while others use a moving laser beam.
6.Material Properties: The material being hardened can also affect the
process. For example, different materials have different absorption
coefficients for laser energy, which can affect the depth and hardness of the
hardened layer.
7.Quenching Method: The method used for quenching, such as water, oil, or
air, can also affect the final metallurgical properties of the hardened layer.

28. MATERIALS SUITABLE FOR LBH
• Some examples of materials that are suitable for laser beam hardening include:
1.Carbon steels
2.Tool steels
3.Stainless steels
4.High-speed steels
5.Cast irons
6.Nickel-based alloys
7.Titanium alloys
8.Aluminum alloys
However, the specific material properties, such as the carbon or alloy content, and
the desired properties of the hardened surface, such as the depth and hardness of
the hardened layer, need to be considered when selecting a material for laser beam
hardening. Additionally, it is important to consider the cost and feasibility of the
process for a given material, as well as the potential impact of laser beam hardening
on the final product's properties and performance.

29. LASER BEAM HARDENING TECHNIQUES
• Surface hardening.
• Through–hardening.
• Localized hardening.

30. SURFACE HARDENING
• surface hardening by laser beam is a process of modifying the surface properties
of a material to increase its wear resistance, durability, and overall performance
using a high-energy laser beam. In this process, a hard and wear-resistant layer
is formed on the surface of the material, while the core of the material remains
relatively soft and ductile.
• The laser beam is generated by a laser source and directed through a beam
delivery system to the surface of the material to be hardened. The laser beam is
then focused onto the surface of the material, which creates a small, intense heat-
affected zone. The surface is rapidly heated to a temperature above the
transformation temperature of the material, but below its melting point.

31. SURFACE HARDENING
• The localized heating of the surface causes a change in the microstructure
and mechanical properties of the material. The surface layer undergoes a
phase transformation, resulting in the formation of a hard and wear-resistant
layer. The thickness of the hardened layer depends on several factors,
including the laser power, scanning speed, and material properties.
• After the laser beam is turned off, the surface is quickly quenched, usually by
spraying water or oil onto the surface, to rapidly cool it and form a hard layer.
The quenching medium cools the surface rapidly, which induces compressive
stresses in the surface layer. These compressive stresses enhance the wear
resistance and fatigue strength of the surface.
• Surface hardening by laser beam is commonly used in the manufacturing of
various components and parts for industries such as automotive, aerospace,
and heavy machinery. By improving the surface properties of the material,
surface hardening by laser beam can enhance the performance, durability,
and service life of the product.

32. Through-hardening
• Through hardening by laser beam is a process of modifying the mechanical
properties of a material by heating it to a high temperature using a high-energy laser
beam, and then rapidly cooling it to form a hard and wear-resistant layer throughout
the entire cross-section of the material. Unlike surface hardening, which forms a hard
layer only on the surface of the material, through hardening by laser beam modifies
the entire cross section of material
1.Heating: The high-energy laser beam is directed onto the surface of the material to
be hardened. The laser beam is then rapidly scanned across the surface of the
material, heating the entire cross-section of the material to a high temperature,
typically above its austenitizing temperature.
2.Soaking: After the material is heated, it is held at a high temperature for a period of
time, typically a few seconds, to ensure that the material is uniformly heated
throughout its cross-section. This process is called soaking.
3.Cooling: Once the material has been soaked, it is rapidly cooled, typically by
quenching in a bath of water or oil, to form a hard and wear-resistant layer
throughout the entire cross-section of the material.

33. LOCALIZEED HARDENING
• Localized hardening is a process of modifying the mechanical properties of a
specific region or area on the surface of a material to increase its wear
resistance, durability, and overall performance. This process involves heating
a specific area of the material to a high temperature using a localized heat
source, such as a flame or a laser beam, and then rapidly cooling the heated
area to form a hard and wear-resistant layer.
• The localized hardening process can be achieved by various methods,
including flame hardening, induction hardening, and laser beam hardening. In
the case of laser beam hardening, a high-energy laser beam is used as the
heat source, and the material is heated to a high temperature at the point
where the laser beam is focused.

34. LOCALIZEED HARDENING
The localized hardening process involves the following steps:
1.Preparing the surface
2. Focusing the laser beam
3. Heating the material
4. Rapid cooling
The localized hardening process is commonly used in the manufacturing of various
components and parts for industries such as automotive, aerospace, and heavy
machinery. By improving the mechanical properties of a specific area of the
material, localized hardening can enhance the performance, durability, and service
life of the product.

36. INDUSTRIALAPPLICATION OF LBH
• some examples of industrial applications of laser beam hardening:
1. Tool and Die Industry: The tool and die industry uses laser beam
hardening to improve the wear resistance and tool life of cutting tools,
molds, and dies. The process is also used to repair and restore damaged
or worn tools and dies.
2. Electronics Industry: The electronics industry uses laser beam hardening
to improve the wear resistance and corrosion resistance of various
components, including connectors, pins, and switches.
3. Automotive Industry: laser beam hardening is widely used in the
automotive industry for improving the wear resistance and fatigue life of
various components, including engine valve seats, camshafts, gears, and
transmission shafts.
4. Medical Industry: Laser beam hardening is used in the medical industry
to improve the wear resistance and corrosion resistance of surgical
instruments, dental tools, and implants. The process is also used to create
customized implants with specific surface properties.

37. Types of Lasers in Hardening
• Among various types of lasers CO2, Nd: YAG and diode lasers are the widely
used lasers for hardening in industries.
• Diode lasers: Diode lasers are compact and efficient, making them a popular
choice for laser hardening applications. They emit radiation in the near-infrared
spectrum, typically at a wavelength of around 940-980 nm, which is well absorbed
by metals. This makes them ideal for hardening low-alloyed steels and cast iron.
Diode lasers also have a high wall-plug efficiency, meaning that they require less
electrical power to produce the same amount of laser power as other types of
lasers.

38. Continued…
• Nd:YAG lasers: It emits radiation in the near-infrared spectrum at a wavelength
of around 1060 nm, which is also well absorbed by metals. They are commonly
used for hardening of high-alloyed steels and other materials that are difficult to
harden with other types of lasers. Nd:YAG lasers also have a high beam quality,
which allows for precise and controlled hardening.
• CO2 lasers: It emits radiation in the far-infrared spectrum at a wavelength of
around 10600 nm, which is not well absorbed by metals. However, CO2 lasers can
be used for hardening of materials that have been pre-coated with an absorbing
material, such as carbon black. This makes them useful for hardening materials
that cannot be easily hardened with other types of lasers, such as certain types of
ceramics and composites.

39. Reason…
• The energy input is dependent on the absorptivity of the material. Only a fraction
of the laser energy is absorbed by the material and the remaining portion is
reflected from the surface.
• The absorption of a polished metal surface depends strongly on the wavelength of
irradiation. In the case of steels, the absorptivity increases when the wavelength is
short. The wave length of Nd: YAG laser beam is 1.064 µm where the CO2 laser
beam is 10.6 µm. So the Nd: YAG laser which is having short wave length is
suitable for surface hardening of steel.
• Due to higher wavelength, CO2 laser offers a low coupling interaction with
metallic substances.

40. Continued…
• Before CO2 laser hardening (LH), painting or coating has to be applied on the
base metal to increase the absorption rate.
• The used paint or coating causes pollution and hazardous effects to the
environment.
• In contrast, Nd: YAG laser is emerging as a competitive tool in surface
modification due to the short wavelength and high absorbing rate of the materials
and coating of base material is not needed which is the advantage compared to
CO2 laser.

41. Advantages…
• Low energy usage in comparison with conventional surface heat-treatment
processes
• Energy input can be adjusted in a wide range by changing laser-beam power, with
converging lenses having different focuses at different levels of defocus, and by
choosing different travel speeds of work piece
• The optical system for beam guidance from the source to the work piece surface
can be adjusted to the hardened-layer profile form, i.e., to the exactness of the
product, using lenses and mirrors of different shapes

42. Continued…
• A hardened surface will be obtained by self-quenching of the heated surface layer
• Without any quenching media, the hardening processes are clean and the
workpieces need not be cleaned
• Beam guidance over the work piece surface can be automated
• Heat treatment can be done on small parts
• Good reproducibility of the microstructure and profile of the surface-hardened
layer.

43. Disadvantages…
Some demerits of LSH are as follows:
• high initial investment
• surface preparation is needed in some cases
• protection against radiation is required
• highly skilled operators are needed

44. Nd:YAG Laser Schematic

45. Parameter
Micro Hardness Hardness
Definition A measure of a material's resistance to
indentation or penetration on a small scale.
A measure of a material's resistance to
deformation or scratching on a larger scale.
Testing
Method
A micro indenter is used to apply a small
load (typically less than 1 kg) on a small
area of the material surface, and the
resulting indentation size is measured.
Various methods can be used depending on the
type of material and desired precision, such as
Rockwell, Brinell, or Vickers testing.
Sample Size
Can be performed on very small samples or
specific locations on larger samples.
Generally requires a larger sample size, and
the test location is not as critical.
Applications Useful for characterizing surface properties,
coatings, and small features or structures.
Used in a wide range of industries to evaluate
the mechanical properties of materials,
including metals, ceramics, plastics, and
composites.
Limitations Results may be influenced by surface
roughness or microstructural features.
Results may be affected by sample preparation,
such as surface finish or heat treatment.
Examples Knoop, Berkovich, or Vickers hardness
tests.
Rockwell, Brinell, or Vickers hardness tests.

46. Wear Resistance
• The tribological properties and the durability of automobile components such as
camshafts, crankshafts, brake drums, internal combustion engine valve and valve
seat and gears were improved by this method.
• One of the traditional methods to increase the wear resistance is induction
hardening, which gives a homogenous microstructure with good wear resistance
but expensive to implement.
• To cancel out wear in tribological systems it is not always necessary to provide the
entire surface with a wear resistant layer.
• Depending upon the application, it is sufficient to harden locally the load bearing
areas which are subjected to wear.

47. Continued…
• Such areas can be treated properly by a laser, either totally or partially.
With the effective use of high power laser sources the peak point of
hardenability and fineness in microstructure can be obtained.
• LH of En18 steel with CO2 laser with laser power of 1.3 and 1.5 kW,
scan velocity 1 m min–1 and a beam diameter of 3 mm increased the
hardness of the base metal from 250 to 900 HV0.2 and a two-fold
increase in wear resistance.
• Hence, the laser surface-hardening technique can be used in the
automobile industries to increase the service life of camshafts and
crankshafts made of En18 steel.

48. En18 Steel
• En18 steel is a low alloy steel with a composition that is primarily defined by the
European Norm EN 10084.
The composition of En18 steel is as follows:
• Carbon (C): 0.15-0.20%
• Manganese (Mn): 0.60-1.00%
• Silicon (Si): 0.10-0.35%
• Chromium (Cr): 0.80-1.10%
• Nickel (Ni): 1.40-2.00%
• Phosphorus (P): maximum 0.040%
• Sulfur (S): maximum 0.040%
• En18 steel is a case-hardening steel that is used in the manufacture of gears, axles,
and other high-stress components. It has good strength and toughness properties,
as well as good wear resistance.

49. Continued…
• Penetration depth of the micro-hardness changes mainly with the laser irradiating
parameters that recursively results in different microstructures.
• This shows that appropriate control of the laser irradiation parameters allowed the
fulfilment of highest micro-hardness at the outermost surface.
• The hardness profile for laser-hardened samples at 1.5 and 1.3 kW under a scan
speed of 1 m min–1 and with a beam diameter of 3 mm.

51. Laser hardening in increasing %carbon in
Steels
• The effect of carbon percentage on the hardness achieved through laser hardening
of steel can be significant. Generally, an increase in carbon content leads to an
increase in hardness after laser hardening. This is because carbon is a key factor in
determining the hardness of steel, as it contributes to the formation of carbides that
can increase the material's hardness.
• In general, low carbon steels (up to 0.3% carbon) are not commonly used for laser
hardening, as they have lower hardenability and may not achieve the desired
hardness levels. Medium carbon steels (0.3-0.6% carbon) are more commonly
used for laser hardening, as they have good hardenability and can achieve higher
hardness levels after laser hardening. High carbon steels (above 0.6% carbon) can
also be used, but they may be more prone to cracking during the laser hardening
process due to their higher carbon content.

52. Continued…
• However, the relationship between carbon content and laser hardening hardness is
not straightforward and can be influenced by other factors, such as the specific
laser hardening process used, the heating and cooling rates, and the presence of
other alloying elements in the steel.
• Overall, the effect of carbon content on laser hardening hardness is complex and
depends on several factors. However, in general, an increase in carbon content
tends to lead to an increase in hardness after laser hardening.

53. Continued…
The factors that can influence the relationship between carbon content and hardness
achieved through laser hardening include:
• Laser hardening process: Different laser hardening processes, such as continuous
wave or pulsed laser, can have different effects on the final hardness achieved. For
example, pulsed laser can provide a more precise and controlled heating and
cooling rate, leading to higher hardness.
• Heating and cooling rates: The heating and cooling rates during laser hardening
can affect the microstructure and resulting hardness.
• Other alloying elements: The presence of other alloying elements in the steel, such
as chromium or molybdenum, can also affect the final hardness achieved through
laser hardening. These elements can promote the formation of specific
microstructures, such as carbides or martensite, that can influence hardness.

54. Continued…
• Steel chemistry: The overall chemistry of the steel, including impurities and grain
size, can also affect the hardenability and final hardness achieved through laser
hardening.
• Laser parameters: The specific laser parameters used during laser hardening, such
as laser power, beam diameter, and scanning speed, can all influence the resulting
hardness. The selection of these parameters will depend on the specific steel being
used and the desired hardness profile.

56. Overlapping Zones

57. Continued…
• The zones between two tracks were considered to be overlapping zones.
• When the laser heat treatment is required for a large surface area, the overlapping
method is used. Conventional overlapping method results in adverse tempering
effect and an irregular surface hardness.
• The optimum gap between centre-to-centre distances between the beam overlap
regions of laser scanning is required. They observed that the 2 mm gap between
laser beams is more appropriate. There is no significance in reducing the gap
below 2 mm in multi-pass laser scanning

58. Effect of different multi-pass distances on the variation of micro hardness across a
transverse section

59. Conclusion
1.The process involves the use of a high-energy laser beam to rapidly heat the surface of the
metal, followed by quenching to produce a hardened surface layer.
2.Laser beam hardening is a surface modification process used to increase the hardness and
wear resistance of metals.
3.The depth of the hardened layer can be controlled by adjusting the laser power and the
duration of the heating process.
4.Laser beam hardening is commonly used in the aerospace, automotive, and manufacturing
industries to improve the performance and lifespan of metal components subjected to high
levels of wear and tear.

60. References
Rana, J., Goswami, G.L., Jha, S.K. Mishra, P.K. and Prasad, B.V.S.S.S. (2007)
‘Experimental studies on the microstructure and hardness of laser-treated steel
specimens’, Optics and Laser Technology, Vol. 39, pp.385–393.
Grum, J. and Sturm, R. (1997) ‘Laser surface melt-hardening of gray and nodular
irons’, Applied Surface Science, Vols. 109/110, pp.128–132.
Babu, P.D., Balasubramanian, K.R. and Buvanashekaran, G. (2011) “Laser surface
hardening: A Review,” International Journal of Surface Science and Engineering,
5(2/3), p. 131. Available at: https://doi.org/10.1504/ijsurfse.2011.041398.