Chapter 37:Surface Engineering

DeGarmo’s Materials and Processes in Manufacturing

37.1 Introduction

Surface Profiles

FIGURE 37-1 Machining processes produce surface flaws, waviness, and roughness that can influence the performance of the component.

Machined Surfaces

Machined Surfaces

FIGURE 37-2 (a) Terminology used in specifying and measuring surface quality; (b) symbols used on drawingby part designers, with definitions of symbols; (c) lay symbols; (d) lay symbols applied on drawings.

SurfaceMeasurement

FIGURE 37-3 (a) Schematic of stylus profile device for measuring surface roughness and surfaceprofile with two readout devices shown: a meter for AA or rms values and a strip chart recorder forsurface profile. (b) Profile enlarged. (c) Examples of surface profiles.

Surface Finish Measurement

FIGURE 37-4 Typical machinedsteel surface as created by facemilling and examined in the SEM. Amicrograph (same magnification) ofa 0.00005-in. stylus tip has beensuperimposed at the top.

SEM Micrograph

FIGURE 37-5 (a) SEMmicrograph of a U.S. dime,showing the S in the wordTRUST after the region has beentraced by a stylus-type machine.(b) Topographical map of the Sregion of the word TRUST from aU.S. dime [compare to part (a)].

Roughness

FIGURE 37-6 Comparison of surface roughness produced by common production processes.(Courtesy of American Machinist.)

Surface Deformation

FIGURE 37-7 Plasticdeformation in the surface layerafter cutting shown in a micrograph at 120X.

Surface Damage as a Function of Rake Angle

FIGURE 37-8 The depthof damage to the surface of amachined part increases withdecreasing rake angle of thecutting tool.

Fatigue Strength as a Function of Finish

FIGURE 37-9 Fatigue strengthof Inconel 718 components aftersurface finishing by grinding orEDM. (Field and Kahles, 1971).

Shot Peening

FIGURE 37-10 & 11 (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.

37.2 Abrasive Cleaning and Finishing

Finishing Barrel

FIGURE 37-12 Schematic ofthe blow of material in tumblingor barrel finishing. The parts andmedia mass typically account for50 to 60% of capacity.

Synthetic Media Geometry

FIGURE 37-13 Syntheticabrasive media are available in awide variety of sizes and shapes.Through proper selection, themedia can be tailored to theproduct being cleaned

Vibration Finishing Tub

FIGURE 37-14 Schematic diagram of a vibratory-finishing tub loaded with parts andmedia. The single eccentric shaft drive provides maximum motion at the bottom, which decreasesas one moves upward. The dualshaft design produces moreuniform motion of the tub and reduces processing time

Media to Part Ratio

Part Examples

FIGURE 37-15 A variety of parts before and after barrelfinishing with triangular-shaped media. (Courtesy of NortonCompany.)

37.3 Chemical Cleaning

37.4 Coatings

Organic Finishes

Electroplating Processes

FIGURE 37-16 Basic steps inthe electrocoating process

Powder Coating

Powder Coating Systems

FIGURE 37-17 A schematic of a powder coating system. The wheels on the color modules permit it to beexchanged with a spare module to obtain the next color.

Electroplating Circuitry

FIGURE 37-18 Basic circuit foran electroplating operation,showing the anode, cathode(workpiece), and electrolyte(conductive solution).

Electroplating Design Recomendations

FIGURE 37-19 Designrecommendations forelectroplating operations

Anodizing

FIGURE 37-20 The anodizing processhas many steps.

Nickel Carbide Plating

FIGURE 37-21 (Left) Photomicrograph of nickel carbide plating produced by electroless deposition. Noticethe uniform thickness coating on the irregularly shaped product. (Right) High-magnification cross sectionthrough the coating. (Courtesy of Electro-Coatings Inc.)

37.5 Vaporized Metal Coatings

37.6 Clad Materials

37.7 Textured Surfaces

37.8 Coil-Coated Sheets

37.9 Edge Finishing and Burrs

Burr Formation

FIGURE 37-22 Schematicshowing the formation of heavyburrs on the exit side of a milledslot. (From L. X. Gillespie,American Machinist, November1985.)

Deburring Allowance

Burr Prevention

FIGURE 37-23 Designingextra recesses and grooves into apart may eliminate the need todeburr. (From L.X. Gillespie,American Machinist, November1985.)