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Gas Nitriding

Gas Nitriding


Metal parts manufacturers often apply industrial surface treatments during finishing to modify metal parts in order to create desired effects in their products. The finishing treatment may change various aspects of a component's appearance or performance. Some parts undergo a series of surface treatments.

For example, a manufacturer may apply a powder paint coating to the exterior of a part in order to produce a desired surface color change, or to help modify the texture or the luster of the surface. Other surface treatments help waterproof components or enhance surface durability and corrosion resistance. Manufacturers utilize many different surface treatments to achieve a variety of goals.

 

The Gas Nitriding Process

The gas nitriding process (also called "ammonia nitriding") provides a way to case harden the surface of steel components, hardening them to better resist scratches, abrasions and scuffing while permitting the interior to remain soft. It represents one of three popular methods for promoting the formation of a nitride layer across the exterior of metal components through nitriding.

Manufacturers perform this case hardening process by exposing a metal work piece to ammonia in a heated environment. As the ammonia begins breaking down into its constituent elements, nitrogen will diffuse across the exterior of the work piece. It forms nitride deposits on the surface. This crust effectively helps case harden the metal work piece.

 

Case Hardening Technology

Gas nitriding today usually relies upon ammonia as the main source of nitrogen for nitride formation. Manufacturers can obtain this commercially available gas comparatively inexpensively for industrial use. During former eras, this form of nitriding required the use of a blast furnace due to the dangers of heating ammonia gas. Today, industrial furnaces supply carefully computer-controlled temperatures, permitting nitriding to take place within closely controlled environments. Additionally, automation has increased the safety and convenience of this process.

Manufacturers can obtain ammonia today in a liquefied form, allowing easier transportation, storage and handling. When companies expose steel parts to ammonia in an industrial furnace under controlled conditions, the heat causes the nitrogen atoms in the ammonia to partially separate and diffuse across the component's surface, forming a nitride crust. The formation of a nitride layer helps harden the surface of the part by improving the metal's ability to withstand scratches and abrasions.

 

GAS NITRIDING: Materials And Applications

Gas nitriding has become an important finishing step in the production of some metal parts. Manufacturers often utilize highly cost-effective materials to complete this type of hardening treatment. Today, numerous applications exist for components produced using this technology.

Materials

The metal parts subjected to gas nitriding typically consist of low carbon steels. However, manufacturers have employed this surface treatment to harden other metals too. Other popular metals sometimes subjected to this treatment include stainless steel, medium and high carbon steel alloys, titanium, molybdenum and even (in rare cases), aluminum.

Ammonia gas represents the most common source of raw material supplying nitrogen for this case hardening method. However, potentially other nitrogenous gases may also serve as raw materials for the gas nitriding process. Manufacturers do require a heating source capable of generating high temperatures, as well as a way to control and monitor the temperature and the nitrogen level. Within a heated environment, ammonia begins breaking down into its constituent nitrogen and hydrogen atoms.

Nitrogen will diffuse across exposed metal surfaces to form a nitride layer. In the past, gas nitriding sometimes resulted in the creation of parts with nitride depositions of variable thicknesses due to production inconsistencies. Today however, manufacturers have developed the capability to control metal alloy compositions, nitrogen levels, temperatures and gas exposure times so precisely they can produce parts with predictable and measurable nitride layers.

Applications

Since nitriding facilitates the production of a hard nitride layer over the surface of metal parts, this technology enjoys popularity in economic sectors and industries requiring more rigid, case hardened tools. This hardening treatment remains a popular application for tools used in die casting and forging. It also helps harden valves, ball bearings, cam shafts, gears, shafts, injectors, firearm components, injectors, and a variety of construction tool surfaces, including hammer heads and chisels.

 

Advantages of Gas Nitriding

As a technology for performing nitriding, gas nitriding offers several advantages.

  1. This process today occurs within precisely controlled parameters. It usually takes place within a temperature-regulated furnace. The ability to automate the process precisely enables manufacturers to control the rate of nitride formation on the surface and to create exterior nitride crusts of measurable thicknesses. In the past, metal parts producers lacked the capability to monitor temperatures and exposure times accurately, so gas nitriding did not involve the same level of precision.
  2. Currently some manufacturers rely upon large temperature-controlled furnaces to produce finished metal parts in bulk using ammonia nitriding. The ability to generate a high volume of surface treated products efficiently has made this technology increasingly popular.
  3. The price of this technology has decreased significantly during recent years. As costs have fallen, the use of gas nitriding has become a more accessible surface treatment. Since components subjected to gas nitriding offer enhanced hardness and wear resistance, these higher quality metal parts supply competitive advantages in the marketplace. Gas nitriding presently assists companies in developing cost-effective components.
  4. The environmental safety of this form of surface treatment has improved in recent years. As computers increasingly control furnace operations, the ability to regulate production parameters with precision has increased. Unlike salt bath nitriding (which sometimes generates high volumes of toxic waste), highly controlled efficient ammonia nitriding does not create as many environmental cleanup problems.

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