Surface integrity is the surface condition of a workpiece after being modified by a

manufacturing Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a ...

process. The term was coined by Michael Field and John F. Kahles in 1964.. The surface integrity of a workpiece or item changes the material's properties. The consequences of changes to surface integrity are a

mechanical engineering Mechanical engineering is the study of physical machines that may involve force and movement. It is an engineering branch that combines engineering physics and mathematics principles with materials science, to design, analyze, manufacture, ...

design problem, but the preservation of those properties are a manufacturing consideration. Surface integrity can have a great impact on a parts function; for example,

Inconel Inconel is a registered trademark of Special Metals Corporation for a family of austenitic nickel-chromium-based superalloys. Inconel alloys are oxidation- corrosion-resistant materials well suited for service in extreme environments subjected ...

718 can have a

fatigue limit The fatigue limit or endurance limit is the stress level below which an infinite number of loading cycles can be applied to a material without causing fatigue failure. Some metals such as ferrous alloys and titanium alloys have a distinct limit, ...

as high as after a gentle

grinding Grind is the cross-sectional shape of a blade. Grind, grinds, or grinding may also refer to: Grinding action * Grinding (abrasive cutting), a method of crafting * Grinding (dance), suggestive club dancing * Grinding (video gaming), repetitive and ...

or as low as after

electrical discharge machining Electrical discharge machining (EDM), also known as spark machining, spark eroding, die sinking, wire burning or wire erosion, is a metal fabrication process whereby a desired shape is obtained by using electrical discharges (sparks). Material i ...

(EDM)..

Definition

There are two aspects to surface integrity: ''topography characteristics'' and ''surface layer characteristics''. The topography is made up of surface roughness,

waviness Waviness is the measurement of the more widely spaced component of surface texture. It is a broader view of roughness because it is more strictly defined as "the irregularities whose spacing is greater than the roughness sampling length". It can ...

, errors of form, and flaws. The surface layer characteristics that can change through processing are:

plastic deformation In engineering, deformation refers to the change in size or shape of an object. ''Displacements'' are the ''absolute'' change in position of a point on the object. Deflection is the relative change in external displacements on an object. Strai ...

residual stress In materials science and solid mechanics, residual stresses are stresses that remain in a solid material after the original cause of the stresses has been removed. Residual stress may be desirable or undesirable. For example, laser peening im ...

es, cracks,

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion (mechanical), abrasion. In general, different materials differ in their hardn ...

, overaging,

phase changes In chemistry, thermodynamics, and other related fields, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states ...

, recrystallization, intergranular attack, and

hydrogen embrittlement Hydrogen embrittlement (HE), also known as hydrogen-assisted cracking or hydrogen-induced cracking (HIC), is a reduction in the ductility of a metal due to absorbed hydrogen. Hydrogen atoms are small and can permeate solid metals. Once absorbe ...

. When a traditional manufacturing process is used, such as machining, the surface layer sustains local plastic deformation.. The processes that affect surface integrity can be conveniently broken up into three classes: ''traditional processes'', ''non-traditional processes'', and ''finishing treatments''. Traditional processes are defined as processes where the tool contacts the workpiece surface; for example:

turning Turning is a machining process in which a cutting tool, typically a non-rotary tool bit, describes a helix toolpath by moving more or less linearly while the workpiece rotates. Usually the term "turning" is reserved for the generation ...

, and machining. These processes will only damage the surface integrity if the improper parameters are used, such as dull tools, too high feed speeds, improper coolant or lubrication, or incorrect grinding wheel hardness. Nontraditional processes are defined as processes where the tool does not contact the workpiece; examples of this type of process include EDM,

electrochemical machining Electrochemical machining (ECM) is a method of removing metal by an electrochemical process. It is normally used for mass production and is used for working extremely hard materials or materials that are difficult to machine using conventional me ...

, and

chemical milling Chemical milling or industrial etching is the subtractive manufacturing process of using baths of temperature-regulated etching chemicals to remove material to create an object with the desired shape. Other names for chemical etching incl ...

. These processes will produce different surface integrity depending on how the processes are controlled; for instance, they can leave a stress-free surface, a remelted surface, or excessive surface roughness. Finishing treatments are defined as processes that negate surface finishes imparted by traditional and non-traditional processes or improve the surface integrity. For example, compressive residual stress can be enhanced via

peening In metallurgy, peening is the process of working a metal's surface to improve its material properties, usually by mechanical means, such as hammer blows, by blasting with shot (shot peening), or focusing light ( laser peening). Peening is norm ...

roller burnishing Roller burnishing is a surface finishing technique where hardened rollers cold work surface imperfections to reduce surface roughness. Roller burnishing differs from abrasive surface finishing techniques in that material is displaced rather than ...

or the recast layer left by EDMing can be removed via chemical milling.. Finishing treatments can affect the workpiece surface in a wide variety of manners. Some clean and/or remove defects, such as scratches, pores,

burr Burr may refer to: Places * Burr (crater), on the Jovian moon Callisto *Burr, Minnesota, an unincorporated community, United States * Burr, Missouri, an unincorporated community, United States *Burr, Nebraska, a village, United States * Burr, Sa ...

flash Flash, flashes, or FLASH may refer to: Arts, entertainment, and media Fictional aliases * Flash (DC Comics character), several DC Comics superheroes with super speed: ** Flash (Barry Allen) ** Flash (Jay Garrick) ** Wally West, the first Kid F ...

, or blemishes. Other processes improve or modify the surface appearance by improving smoothness, texture, or color. They can also improve

corrosion resistance Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...

wear Wear is the damaging, gradual removal or deformation of material at solid surfaces. Causes of wear can be mechanical (e.g., erosion) or chemical (e.g., corrosion). The study of wear and related processes is referred to as tribology. Wear in ...

resistance, and/or reduce

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding (motion), sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative la ...

Coating A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. Powde ...

s are another type of finishing treatment that may be used to

plate Plate may refer to: Cooking * Plate (dishware), a broad, mainly flat vessel commonly used to serve food * Plates, tableware, dishes or dishware used for setting a table, serving food and dining * Plate, the content of such a plate (for example: ...

an expensive or scarce material onto a less expensive base material.

Variables

Manufacturing processes have five main variables: the workpiece, the

tool A tool is an object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many animals use simple tools, only human beings, whose use of stone tools dates ba ...

, the

machine tool A machine tool is a machine for handling or machining metal or other rigid materials, usually by cutting, boring, grinding, shearing, or other forms of deformations. Machine tools employ some sort of tool that does the cutting or shaping. All ...

, the environment, and process variables. All of these variables can affect the surface integrity of the workpiece by producing: *High temperatures involved in various machining processes *Plastic deformation in the workpiece (residual stresses) *Surface geometry (roughness, cracks, distortion) *

Chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and break ...

s, especially between the tool and the workpiece

References

Bibliography

*{{Citation , last = Degarmo , first = E. Paul , last2 = Black , first2 = J T. , last3 = Kohser , first3 = Ronald A. , title = Materials and Processes in Manufacturing , publisher = Wiley , year = 2003 , edition = 9th , isbn = 0-471-65653-4. Mechanical engineering Metallurgy Plastics industry 1964 introductions