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 drawing by part designers, with definitions of symbols; (c) lay symbols; (d) lay symbols applied on drawings.

Surface Measurement FIGURE 37-3 (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 37-4 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 37-5 (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 37-6 Comparison of surface roughness produced by common production processes. (Courtesy of American Machinist.)

Surface Deformation FIGURE 37-7 Plastic deformation in the surface layer after cutting shown in a micrograph at 120X.

Surface Damage as a Function of Rake Angle FIGURE 37-8 The depth of damage to the surface of a machined part increases with decreasing rake angle of the cutting tool.

Fatigue Strength as a Function of Finish FIGURE 37-9 Fatigue strength of Inconel 718 components after surface finishing by grinding or EDM. (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 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 37-13 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 37-14 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 37-15 A variety of parts before and after barrel finishing with triangular-shaped media. (Courtesy of Norton Company.)

37.3 Chemical Cleaning

37.4 Coatings

Organic Finishes

Electroplating Processes FIGURE 37-16 Basic steps in the 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 be exchanged with a spare module to obtain the next color.

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

Electroplating Design Recomendations FIGURE 37-19 Design recommendations for electroplating operations

Anodizing FIGURE 37-20 The anodizing process has many steps.

Nickel Carbide Plating FIGURE 37-21 (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.)

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 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

Burr Prevention FIGURE 37-23 Designing extra recesses and grooves into a part may eliminate the need to deburr. (From L.X. Gillespie, American Machinist, November 1985.)