Surface Engineering

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 strengthof Inconel 718 components aftersurface finishing by grinding orEDM. (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 drawingby part designers, with definitions of symbols; (c) lay symbols; (d) lay symbols applied on drawings.

SurfaceMeasurement

FIGURE 35-4 (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 35-5 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 35-6 (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 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 ofthe blow of material in tumblingor barrel finishing. The parts andmedia mass typically account for50 to 60% of capacity.

Synthetic Media Geometry

FIGURE 35-9 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 35-10 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 35-11 A variety of parts before and after barrelfinishing with triangular-shaped media. (Courtesy of NortonCompany.)

35.3 Chemical Cleaning

35.4 Coatings

Organic Finishes

Electroplating Processes

FIGURE 35-12 Basic steps inthe 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 beexchanged with a spare module to obtain the next color.

Electroplating Circuitry

FIGURE 35-14 Basic circuit foran electroplating operation,showing the anode, cathode(workpiece), and electrolyte(conductive solution).

Electroplating Design Recomendations

FIGURE 35-15 Designrecommendations forelectroplating operations

Anodizing

FIGURE 35-16 The anodizing processhas many steps.

Nickel Carbide Plating

FIGURE 35-17 (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.)

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

Deburring Allowance

35.10 Surface Integrity

Burr Prevention

FIGURE 35-19 Designingextra recesses and grooves into apart may eliminate the need todeburr. (From L.X. Gillespie,American Machinist, November1985.)

Surface Deformation

FIGURE 35-20 Plasticdeformation in the surface layerafter cutting. (B. W. Kruszynskiand C. W. Cuttervelt, AdvancedManufacturing 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 depthof damage to the surface of amachined part increases withdecreasing rake angle of thecutting tool.

Surface Stress

FIGURE 35-23 (Top) Acantilever-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 stressesinduced by roller burnishing or shot peening. (Bottom) Netstress pattern obtained when loading a surface-treated beam.The reduced magnitude of the tensile stresses contributes toincreased fatigue life.

Fatigue Life with Surface Finish

FIGURE 35-24 Fatigue life ofrotating beam 2024-T4aluminum specimens with avariety of surface-finishingoperations. Note the enhancedperformance that can beachieved by shot peening androller burnishing.