Boronizing

Definition - What does Boronizing mean?

Boronizing is a thermochemical surface-hardening process in which boron atoms are diffused into the surface of a work piece to form complex borides (such as FeB/FeB2) with the base metal.

There is no mechanical interface between the complex borides and the substrate, as this is a true diffusion process. The resulting case layer has a hard, slippery surface capable of performing at higher temperatures than most surface treatments. Practically any ferrous material can be boronized, as well as many nickel, titanium & cobalt alloys. However, it is important to note, the higher the content of alloy elements, the slower the diffusion rate.

Boronizing is used to improve the life and performance of metal components. The boronizing process:

  • Strengthens resistance to corrosion
  • Strengthens resistance to acid
  • Strengthens resistance to abrasive wear
  • Decreases coefficient of friction
  • Increases surface hardness

Examples of applications include pumps, valves, and impellers. Extremely heavy abrasion and erosion resistance properties make it suitable for the oil, mining, and agricultural industries.

Boronizing is also known as boriding.

Corrosionpedia explains Boronizing

Boronzing is a metallurgical surface preparation method by which metal is heated within a boron-rich environment in order to increase wear resistance. It is a boron diffusion process where a hard, wear-resistant case can be formed under the surface of a wide variety of ferrous and non-ferrous material. The boriding process involves the use of specially formulated boron-yielding material heated to temperatures between 1300 and 1830°F.

During the boronizing process, boron atoms diffuse into the metal surface and form metal borides. The surface boride may be in the form of either a single phase or a double phase boride layer. With ferrous materials, the boride layers attain a hardness of between 1500HV to 2300HV. Boronized metal parts are extremely wear resistant and will often last two to five times longer than components treated with conventional heat treatments such as:

  • Hardening
  • Carburizing
  • Nitriding
  • Nitrocarburizing
  • Induction hardening

The boron diffusion process is a two-step reaction. The first step is a reaction between the boron-yielding substance or compound and the part, which is a function of time and temperature. This results in a thin, dense boride layer. This reaction is followed by diffusion, which is a faster process.

The thickness of the boride layers varies according to:

  • Temperature
  • Treatment time
  • Material

The FeB layer, while harder, is more brittle and more prone to fracture upon impact.

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