During industrial metal parts fabrication, manufacturers frequently seek to harden the exterior of steel work pieces to enhance wear resistance. Also called "surface hardening", this case hardening process typically relies upon thermochemical processes to transform the outer layer of a metal object. Metallurgists depend upon several different available technologies for achieving surface hardening, including carburizing, induction hardening and nitriding.
The Nitriding Process
Nitriding involves the diffusion of nitrogen across the surface of steel in order to harden the outer layers of metallic work pieces. This process may create a brittle exterior which resists abrasion more effectively. At high temperatures, nitrogen will combine with alloys in ferrous metals to form hardened nitrides.
Manufacturers can use a variety of techniques to accomplish conventional nitriding. Typically, they depend upon ammonia gas to supply nitrogen for the nitriding process. By heating some alloys in the presence of ammonia at temperatures ranging between 950 degrees Fahrenheit and 1050 degrees Fahrenheit during sustained periods of time, they can effectively case harden the outer layer of steel components. A comparatively recently developed alternative to conventional industrial nitriding involves the use of plasma nitriding, a process sometimes called "ion nitriding" or "ionic nitriding".
The History of Plasma Nitriding
Initially investigated during the 1920s, the process of plasma nitriding gained greater acceptance during the late 1930s and early 1940s. Arc welding as a technology spread extensively in industrial fabrication environments during this period of intense military armaments manufacturing.
Today, computerization has contributed to numerous automated fabrication processes, including ionic nitriding. Processes which at one time required direct human supervision now occur more accurately and uniformly as a result of the use of computerized control technologies. In many modern high volume metal parts industrial production environments, automation permits the cost-effective finishing of work pieces using ion nitriding.
The Process of Plasma Nitriding
During basic plasma nitriding, manufacturers establish a vacuum around a metal work piece using gases and, with the assistance of an electrical charge, send a steady cascade of nitrogen ions into the surface of a metal part. This process necessarily occurs at high temperatures. The bombardment of ions helps temper the metal, creating a fine, hard finished superficial outer layer.
The case hardening depth of finishing achieved through plasma nitriding varies based upon the constituent alloys in metal work pieces. During automated ionic nitriding, manufacturers typically rely upon vacuum chambers and highly controlled time and temperature parameters to achieve uniform surface finishes.
Plasma Nitriding Applications
Plasma nitriding enjoys numerous applications in high tech industrial component fabrication environments. The ability to harden metal surfaces selectively and uniformly offers great utility to manufacturers in a multitude of industries.
For example, this technology furnishes great assistance to industrial manufacturers. It allows the generation of numerous parts used in other fabrication processes, such as the plastics industry. Components of automated plastics-manufacturing machinery which sustain heavy regular use may benefit from surface hardening through plasma nitriding. For instance, injector pins, extrusion dies, stamping components and other machinery required for production usually withstands wear better if plastics manufacturing machinery fabricators select case hardened parts. Plasma nitriding helps finish many of these components.
Plasma nitriding has also greatly assisted manufacturers in transportation industries. This finishing process promotes selectively hardened metallic surfaces. It enables gears, ball bearings, cam shafts, valves, pistons and other engine parts to withstand the rigors of challenging mechanical environments for longer periods of time.
Nitriding: Using Plasma Vs Gas
Plasma nitriding offers a number of advantages over conventional nitriding conducted with the assistance of ammonia gas. For instance, although both processes occur at high temperatures, plasma nitriding does not require the use of a blast furnace. Additionally, parts manufacturers can control the application of plasma nitriding finishes with great precision, a difficult objective to achieve with the use of gas.
The surfaces resulting from plasma nitriding displays a hard, uniform finish, without the brittleness often associated with gaseous nitriding technologies. While parts which undergo conventional nitriding using gas (such as ammonia) often require additional finishing operations, such as grinding and polishing, the bombardment of the surface with nitrogen ions generates a fine, smooth texture. Reliance upon this technology may eliminate the necessity for additional finishing operations.
Finally, today plasma nitriding typically offers a more environmentally friendly manufacturing process than conventional low tech nitriding. The latter often occurs in conjunction with surface preparation techniques involving the use of cyanide salt baths. Clean up following production often requires the disposal of toxic (and potentially hazardous) materials. In this respect, automated plasma nitriding processes use components more efficiently and therefore generate less waste.
Plasma Nitriding Vs Chrome Electroplating
Industrial parts manufacturing sometimes relies upon the process of chrome electroplating to help finish metal work pieces. Typically, they depend upon a series of salt baths to prepare the surface and then use the application of electricity to help coat the prepared site with a hard metallic finish, such as chrome. Chrome electroplating creates an attractive, shiny and reflective surface very cost-effectively.
Plasma nitriding offers a superior finishing technique in some production environments, however. It also hardens the exterior of a metal work piece. Additionally, since plasma nitriding diffuses over the surface, this process eliminates the flaking issues or uneven application problems sometimes associated with chrome electroplating.
While electroplated chrome finishes eventually dull and wear away from the surface of metal parts subjected to heavy use, plasma nitriding will offer better overall wear resistance through the course of years. These finished surfaces also withstand corrosion more effectively in some circumstances.