Boriding (Boronizing) of Steels,Boriding (Boronizing) of Steels,Boriding (Boronizing) of Steels,Boriding (Boronizing) of Steels
Introduction
BORIDING, or boronizing, is a thermo-chemical surface hardening process that can be applied to a wide variety of
ferrous, nonferrous, and cermet materials. The process involves heating well-cleaned material in the range of 700 to 1000
°C (1300 to 1830 °F), preferably for 1 to 12 h, in contact with a boronaceous solid powder (boronizing compound), paste,
liquid, or gaseous medium. Other developments in thermochemical boriding include gas boriding techniques such as
plasma boriding and fluidized bed boriding. There is a current trend toward the use of multicomponent boriding.
This article presents mainly the various media used for thermochemical boriding, their advantages, limitations, and
applications. Physical and chemical vapor deposition (PVD and CVD), plasma spraying, and ion implantation are
alternative nonthermo-chemical surface-coating processes for the deposition of boron or codeposition of boron and
metallic element(s) onto a suitable metallic or nonmetallic substrate material. This article briefly describes the CVD
process, which has emerged to be dominant among the metal boride deposition processes.
Characteristic Features of Boride Layers
During boriding, the diffusion and subsequent absorption of boron atoms into the metallic lattice of the component
surface form interstitial boron compounds (Ref 1, 2, 3, 4, 5). The resulting layer may consist of either a single-phase
boride or a polyphase boride layer. The morphology (Fig. 1), growth, and phase composition of the boride layer can be
influenced by the alloying elements in the base material.

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