International Conference on Global Trends in Engineering, Technology and Management (ICGTETM-2016)
An Overview of Alternative Mechanical Surface
Treatments
A. P. Kalmegh#1, P. M. Khodke*2, D. S. Mankar#3
#1
Research student, GCOE, Amravati
2
Principal, GCOE, Karad
Abstract: The aim of this paper is to summarize the
Alternative Mechanical Surface Treatments and its
principle use for improvements of surface properties.
Objective of mechanical surface treatments is
improvement on and
internal nearby surface
properties such as case depth, magnitude of residual
stresses that is mainly compressive, hardness,
roughness, nature of microstructure, porosity, texture,
corrosive properties, stability against mechanical,
thermal and thermo-mechanical loading. This study
would be useful in selection of manufacturing process
of surface treatment in various industries.
3
Research student, GCOE, Amravati
linearly with the logarithm of roughness. It has been
also studied whether the cause for fatigue strength
increases was to be found in the effect of mechanical
work hardening or the effect of induced compressive
residual stresses.
Fig 1 indicates the approaches for the explanation of
changes in fatigue behavior due to mechanical surface
treatments. [9]
Introduction
In past few decades, manufacturing has undergone
notable transformation and has oriented itself to
market demands. The modern manufacturing
industries need to have high production rate, enhanced
flexibility in operation and standard of product quality.
A large number of processes with their limited
characteristics are available as manufacturing Fig 1 fatigue behaviour due to mechanical surface treatments [9]
resources. Each process has its own operating
Basically the objective of the mechanical surface
procedure and capability, in terms of tolerance and
treatments is on near surface properties such as case
surface quality that each can produce.
depth, magnitude of residual stresses (mainly
compressive), hardness, roughness, nature of
Where a component has to withstand heavy load, microstructure, porosity, texture, corrosive properties,
undergo high speed rotation and sustain high stability against mechanical , thermal and thermotemperature, steel alloy is preferred as a raw material. mechanical loading.
Various such applications include aero engines,
transmission
components,
chemical
pumps Several Mechanical Surface treatments are available
components, cylindrical crank pins, cylindrical roller for improving the surface properties. Mechanical
bearings etc. Paper machinery, railway vehicle axle, surface treatments may be roughly divided into:[14]
rolling mill gear box, crusher, printing machinery, i. Cutting- Turning, Planning, honing, milling,
machine tool spindle, hydro-electrical power machine,
grinding, polishing, etc[12]
ship propellers shaft, cranes, extrusion machine, ii. Non Cutting- Shot Peening , Laser shot Peening,
molding machines, gas turbines etc. also find useful
Water Jet Peening, Ultrasonic Peening, Deep
application of steel alloy.
Rolling, Roller Burnishing, Low plasticity
Burnishing, etc ([10],[14])
Product designers constantly strive to design
component that can run last longer and operate more
The main objective of cutting method is for shaping
precisely. Modern development of high speed purpose, whereas the non-cutting methods are used for
equipment or machinery has resulted in higher loading optimal surface layer. Following fig indicates the
and increased speeds of moving parts. Components overview of the principal non-cutting processes of
produced must be accurate, both dimensionally and mechanical surface treatments.
geometrically. Unfortunately, most of the times,
machining processes produce parts with surface that
are either unsatisfactory from the standpoint of
geometrical perfection or quality of surface texture.
Siebel and Gaier [12] stated factor for roughness that
express the effect on fatigue strength and decrease
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International Conference on Global Trends in Engineering, Technology and Management (ICGTETM-2016)
a)
b)
c)
Fig 2 a) Near-surface plastic deformation b) near-surface plastic
strain
c) deformed layer fixed with the bulk of material
(cannot be extended) [4]
The basic principle of all mechanical surface
treatments is localized elastic plastic deformation near
–surface region leads to formation of compressive
residual stresses[4], enabling the strengthened nearsurface region to withstand against fatigue cracks
initiation and propagations. The primary objective of
this paper is to summarize the non-cutting mechanical
surface treatments.
Shot Peening
In shot peening the surface of a part is impinged with
small spherical or cylindrical media of steel, glass or
ceramic. [15] A stream of shots (balls) is striked at the
metal surface at high velocity under controlled
condition, sufficient to create plastic deformation.
Depending on the part geometry, part material, shot
material, shot quality, shot intensity, shot coverage,
shot peening can increase fatigue life from 0-1000 %
[7]. Plastic deformation induces a residual
compressive stresses in a peened surface along with
tensile stress in the interior.
Fig 3 Mechanism of shot peening [7]
Fig 4a Transducer for ultrasonic peening [3]
Fig 4b Using of basic UP system for fatigue life
improvement of tubular welded joint [18].
Water Jet Peening:
In water jet peening impingement of droplets of water
on the surface, generates a surface pressure
distribution producing peak load that exceed the yield
strength of material. The droplets of jet generate high
compressive residual stresses on the water peened
surface. The different process parameters which
influence the process are nozzle geometry, jet pressure,
nozzle to surface distance, peening angle and peening
duration ([2,13]).Also oil jet peening is developed
similar to water jet peening where oil jet is used
instead of water jet to improve the surface
characteristic. [7]
Ultrasonic peening
The Ultrasonic peening (UP) is the combined effect of
high frequency impact of special strikers and
ultrasonic oscillation in treated material [6]. The main
benefit of UP is to relieve the harmful tensile residual
stresses by introducing compressive residual stresses.
The UP can be applied successfully for the increasing
of the fatigue life parts and welded elements,
eliminating of distortion caused by welding and other
technological processes, residual stress-relieving and
increase of hardness of material. ([3],[ 6])
Fig 5 Water jet peening system [2]
In UP magnetostrictive and piezoelectric transducer
can be used. UP is based on the vibration of special
shot using high power ultrasound. The surface of the
specimen to be treated is peened with a very high
number of impacts over a short period of time,
because of high frequency of the system.
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Laser Shot Peening
In Laser Shot Peening (LSP) pulses hit the surface
with high power intensity for the generation of shock
waves. These waves plastically deform the surface and
compressive stresses are introduced into the
subsurface. Effectivity of the process depends on the
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International Conference on Global Trends in Engineering, Technology and Management (ICGTETM-2016)
material (target), laser, beam parameter, absorbent and
transparent overlays properties ([15], [1]). In this
process, a laser beam is used to vaporize a thin opaque
coating, often flat black paint, applied to the surface of
components over the region to be treated.
Fig 8 Principle of low plasticity burnishing [11]
Fig 6 Laser Shock Peening (LSP) Process [1]
Deep Rolling
Deep Cold Rolling (DCR) is a surface treatment
technique which is performed using a roller or ball
type tool to produce a surface residual compressive
stress to improve the fatigue life of materials and
engineering components. As a result of the contact of
a ball with the surface of a component, a longitudinal
groove is created which is accompanied by a plastic
region followed by an elastic zone. After the
separation of ball, the recovery of elastic zone creates
a large residual compressive stress on the surface. A
number of parameters can severely influence the deep
cold rolling process and consequently the near surface
residual stresses. ([12],[17])
1)
The ball rolls across the surface of a component in a
pattern defined in the CNC code, as in any machining
operation. The tool path and normal pressure applied
can be designed to create a distribution of compressive
residual stress. Since there is no shear being applied to
the ball, it is free to roll in any direction. As the ball
rolls over the component, the pressure from the ball
causes plastic deformation to occur in the surface of
the material under the ball. LPB smoothes surface
asperities during machining, leaving an improved,
almost mirror like surface finish.
Following figure indicates the comparative increase in
cold work, „Case depth‟ and fatigue (Igor Altenberger)
workpiece 2) tool F= Rolling force s= feed
Fig 7 Deep Rolling [9]
Low plasticity Burnishing (LPB®)
LPB differs from conventional ball or roller
burnishing in using the minimal amount of plastic
deformation (cold working) needed to create the level
of residual stress to improve fatigue or stress corrosion
performance ([10],[11]). Figure 8 shows the basic
principle of LPB process, in which a ball is supported
in a spherical hydrostatic bearing. The tool can be held
in CNC machine or by industrial robot, depending on
the application. The machine tool coolant is used to
pressurize the bearing with continuous flow of fluid to
support the ball. The ball does not contact the
mechanical bearing seat, even under load. The ball is
loaded at a normal force to the surface of a component
with a hydraulic cylinder that is in the body of the tool.
ISSN: 2231-5381
Fig 9 cold work, case depth and fatigue strength for different
mechanical surface treatments [14]
Here the following table shows comparison of the
different surface treatments (Igor Altenberger). Only
the main difficulty is to compare the treatments with
vast range of the process parameters. [14]
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International Conference on Global Trends in Engineering, Technology and Management (ICGTETM-2016)
Table: 1 comparison of the different surface treatments [14]
4.
Amount
of
residual
stresses
Dislocati
on
density
Surface
microhar
dness
increases
5.
Roller
burnishing
(low
pressure)
Water
peening
Shot
peening
Explosive
hardening
≈σ Yield
Low
medium
< 60 %
≈σ Yield
Low
medium
Very
high
Very
High
?
Ultrasonic
shot
peening
Gravity
peening
Laser
shock
peening
≈σ Yield
High
?
≈σ Yield
High
?
≈σ Yield
Medium
30
–
130 %
dependin
g
on
work
material
60 %
Process
Deep
Rolling
≈σ Yield
≈σ yield
≈σ Yield
High
60% to
150 %
80 %
Maxi
mum
„case
depth
‟
< 0.1
mm
Surface
Roughn
ess
Cold
work
≈1 µm
?
≈0.1
mm
0.3
mm
0.3
to
0.8
mm
0.8
mm
1-2 µm
<
10 %
550 %
?
0.8
mm
2
mm
>>
5
µm
1-5 µm
4-8 µm
< 5 µm
6.
7.
8.
>>
µm
5
?
10 %
9.
1 %
to
20 %
10.
11.
3
mm
≤ 1 µm
>20
%
Conclusion:
All mechanical surface treatments have various
advantages over each other. It is observed during the
review that aspects to be considered during selection
of surface treatment for desirable properties could be
summarized as maximum fatigue strength, less
induced compressive stress, surface finish, higher in
process thermal stability with less cold work
requirements, higher hardness and high corrosion
resistance. These above stated factors should be
focused for achievement of surface desirable
properties depending on the specific application.
LPB® is the registered trademark of Lambda
Technologies group.
12.
13.
14.
15.
16.
17.
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