Chapter 35:
Surface Engineering
DeGarmo’s Materials and Processes in
Manufacturing
35.1 Introduction
Fatigue Strength as a Function of Finish
FIGURE 35-1
Fatigue strength
of Inconel 718
components after
surface finishing by
grinding or
EDM. (Field and
Kahles, 1971).
Surface Profiles
FIGURE 35-2
Machining
processes produce
surface flaws,
waviness, and
roughness that can
influence the
performance of the
component.
Machined
Surfaces
Machined
Surfaces
FIGURE 35-3 (a) Terminology used in specifying and
measuring surface quality; (b) symbols used on drawing
by part designers, with definitions of symbols; (c) lay
symbols; (d) lay symbols applied on drawings.
Surface
Measurement
FIGURE 35-4 (a)
Schematic of stylus
profile device for
measuring surface
roughness and surface
profile with two readout
devices shown: a meter
for AA or rms values and
a strip chart recorder for
surface profile. (b) Profile
enlarged. (c) Examples of
surface profiles.
Surface Finish Measurement
FIGURE 35-5 Typical machined
steel surface as created by face
milling and examined in the SEM. A
micrograph (same magnification) of
a 0.00005-in. stylus tip has been
superimposed at the top.
SEM Micrograph
FIGURE 35-6 (a) SEM
micrograph of a U.S. dime,
showing the S in the word
TRUST after the region has been
traced by a stylus-type machine.
(b) Topographical map of the S
region of the word TRUST from a
U.S. dime [compare to part (a)].
Roughness
FIGURE 35-7 Comparison of
surface roughness produced by
common production processes.
(Courtesy of American Machinist.)
35.2 Mechanical Cleaning and Finishing
Blast Cleaning
Finishing Barrel
FIGURE 35-8 Schematic of
the blow of material in tumbling
or barrel finishing. The parts and
media mass typically account for
50 to 60% of capacity.
Synthetic Media Geometry
FIGURE 35-9
Synthetic
abrasive media are
available in a
wide variety of sizes
and shapes.
Through proper
selection, the
media can be tailored
to the
product being cleaned
Vibration Finishing Tub
FIGURE 35-10
Schematic diagram of a
vibratory-finishing tub
loaded with parts and
media. The single
eccentric shaft drive
provides maximum
motion at the bottom,
which decreases
as one moves upward.
The dualshaft design
produces more
uniform motion of the
tub and reduces
processing time
Media to Part Ratio
Part Examples
FIGURE 35-11 A variety of parts before and after barrel
finishing with triangular-shaped media. (Courtesy of Norton
Company.)
35.3 Chemical Cleaning
35.4 Coatings
Organic Finishes
Electroplating Processes
FIGURE 35-12 Basic steps in
the electrocoating process
Powder Coating
Powder Coating Systems
FIGURE 35-13 A schematic of a
powder coating system. The wheels
on the color modules permit it to be
exchanged with a spare module to
obtain the next color.
Electroplating Circuitry
FIGURE 35-14 Basic circuit for
an electroplating operation,
showing the anode, cathode
(workpiece), and electrolyte
(conductive solution).
Electroplating Design Recomendations
FIGURE 35-15 Design
recommendations for
electroplating operations
Anodizing
FIGURE 35-16 The anodizing process
has many steps.
Nickel Carbide Plating
FIGURE 35-17 (Left) Photomicrograph of nickel carbide
plating produced by electroless deposition. Notice
the uniform thickness coating on the irregularly shaped
product. (Right) High-magnification cross section
through the coating. (Courtesy of Electro-Coatings Inc.)
35.5 Vaporized Metal Coatings
35.6 Clad Materials
35.7 Textured Surfaces
35.8 Coil-Coated Sheets
35.9 Edge Finishing and Burrs
Burr Formation
FIGURE 35-18 Schematic
showing the formation of heavy
burrs on the exit side of a milled
slot. (From L. X. Gillespie,
American Machinist, November
1985.)
Deburring
Allowance
35.10 Surface Integrity
Burr Prevention
FIGURE 35-19 Designing
extra recesses and grooves into a
part may eliminate the need to
deburr. (From L.X. Gillespie,
American Machinist, November
1985.)
Surface Deformation
FIGURE 35-20 Plastic
deformation in the surface layer
after cutting. (B. W. Kruszynski
and C. W. Cuttervelt, Advanced
Manufacturing Engineering,
Vol. 1, 1989.)
Shot Peening
FIGURE 35-21 (a) Mechanism for formation of residual compressive stresses in surface
by cold plastic deformation (shot peening). (b) Hardness increased in surface due to
shot peening.
Surface Damage as a Function of Rake
Angle
FIGURE 35-22 The depth
of damage to the surface of a
machined part increases with
decreasing rake angle of the
cutting tool.
Surface Stress
FIGURE 35-23 (Top) A
cantilever-loaded (bent)
rotating beam, showing
the normal distribution
of surface stresses
(i.e., tension at the top
and compression at the
bottom). (Center) The
residual stresses
induced by roller
burnishing or shot
peening. (Bottom) Net
stress pattern obtained
when loading a
surface-treated beam.
The reduced magnitude
of the tensile stresses
contributes to
increased fatigue life.
Fatigue Life with Surface Finish
FIGURE 35-24 Fatigue life of
rotating beam 2024-T4
aluminum specimens with a
variety of surface-finishing
operations. Note the enhanced
performance that can be
achieved by shot peening and
roller burnishing.