Today metal manufacturers sometimes seek to produce modifications to the exteriors of work pieces during finishing. A surface treatment may alter the color of a metal surface, increase its luster, enhance its electrical conductivity, augment its ability to withstand corrosion and wear, or produce other desired physical changes. The application of specialized coatings has become just one popular type of treatment frequently employed in some industrial settings, for example.
In many situations, manufacturers desire to harden the outer layer of metal while retaining a softer, less brittle, interior. "Case hardening" produces a tough surface shell which enables steel components to resist harsh environmental conditions more effectively. It typically requires the use of stronger tools to penetrate the exterior of case hardened steel components.
A process called "nitriding" offers one useful way for manufacturers to create case hardened products. During this process, nitrogen diffuses across the exterior of a steel work piece which then undergoes surface heating. (The term "nitride" refers to a nitrogen ion, of course. It forms a binary compound of nitrogen with a metal. The commonly accepted chemical formula for a nitride is the symbol N followed by a suprascript of 3-).
The Ionic Nitriding Process
Modern facilities which perform nitriding generally employ equipment which allows them to control specific parameters of this process. By investing in this type of sophisticated production environment, a manufacturer obtains the ability to monitor the formation of the surface nitride layer with greater accuracy. In some cases, it becomes possible to essentially customize this crust, enabling some parts intended for use in settings involving heavy wear or harsh conditions to provide a particularly thick case hardened outer layer.
Ionic nitriding usually occurs with the assistance of specialized equipment, including a temperature controlled vacuum chamber. The manufacturer usually preheats the metal surface inside the vacuum chamber and infuses gas under pressure-controlled conditions to pretreat the surface of the workpiece. This step helps to prepare the surface for the formation of a nitride layer.
During nitriding, the vacuum chamber fills with a carefully calculated mixture of nitrogen, hydrogen and carbon-containing gas (such as methane). The issuance of an electrical charge enables the metal work piece and some components of the chamber to function essentially as a battery system. The manufacturer relies upon the electrical charge to ionize the gas.
When it diffuses across the heated metal part under controlled temperature conditions, the nitrogen forms a binary compound with surface metal within the work piece. It creates a nitride layer of variable thickness along the exterior of the steel. By regulating parameters such as the time of exposure, the alloy composition of constituents, the level of pressure and the temperature, the manufacturer can help control the thickness of the thin, developing nitride crust. The process produces uniformly nitride-layered parts.
IONIC NITRIDING: Materials And Applications
This technology has increased in popularity during recent years. While it does require a significant capital investment, it offers the advantages of a reduced environmental burden. Manufacturers can employ efficient production mechanisms using ionic nitriding.
Steel still remains the most popular metal subjected to ionic nitriding. Reportedly, some manufacturers also perform this process on parts comprised of other ferrous metals, including cast iron. This technology reportedly will also harden some aluminum alloys and titanium alloys. To perform ionic nitriding, the manufacturer typically invests in sophisticated production equipment and plant facilities.
Today ionic nitriding enjoys widespread applications in a number of economic sectors. Firms engaged in industrial tool and equipment manufacturing, transportation, aerospace, construction, medical equipment production, and energy frequently rely upon this type of case hardening to obtain more durable steel products. Metal surfaces subjected to this finishing step generally wear better during the course of use. Ionic nitriding does also increase surface brittleness, so manufacturing companies utilize this process selectively.
Some popular applications for this technology occur in the mechanical parts marketplace. For instance, many engines supply very hot environments imposing heavy wear on some components. Ionic nitriding helps produce gears, cam shafts, and fuel injector pumps capable of withstanding harsher environmental conditions than comparable untreated parts can usually endure. This process also contributes to the production of tools, such as hammers, chisels, and dies. It may help strengthen metal fencing, padlocks and a wide array of construction supplies.
Advantages of Ionic Nitriding
Ionic nitriding offers several important advantages during the manufacturing process.
- It usually offers the benefit of case hardening steel efficiently, without the generation of large quantities of toxic chemical byproducts requiring expensive disposal. Nitriding which depends upon liquid baths may create more hazardous waste handling issues; by contrast, this manufacturing technology occurs entirely within an enclosed vacuum chamber, facilitating easier waste cleanup.
- Ionic nitriding offers a significant degree of flexibility. It readily permits manufacturers to reuse the same equipment to generate highly customized components with different nitride thickness levels. A manufacturer may create a thick nitride layer for some steel components intended for use in challenging environments, while allowing others to reach the market with less extensive nitride crusts, depending upon the needs of individual customers.
- Despite the significant capital investment in production facilities, ionic nitriding may offer substantial economic benefits for manufacturers in terms of the production of high quality, uniform product lines. Unlike the "hit or miss" approach to nitriding involved in using steel nitriding in very low tech settings, ionic nitriding allows the mass production of uniform parts with a known and measurable level of case hardening. This fact contributes to the competitiveness of some finished steel components in the international industrial marketplace.