Boriding (boronizing) is a thermochemical diffusion process in which hard and wear resistant boride layers are generated by diffusing boron onto the surface of material.
The treatment of the materials is carried out in a temperature range of 750 to 950°C. An essential element is the optimal distribution of heat in the furnace used in order to treat all parts of a batch evenly. During the boriding process, complex intermetallic compounds are created between the elements iron, boron, chromium, nickel, vanadium, etc. The resulting borides form a hard peripheral surface layer consisting of Fe2B and other compounds. Because of its crystalline structure, the boride layer is anchored exceptionally well to the base material.
For treatment, the boride may be dispensed in powder, paste or granule form. Single large parts, work pieces and bulk material can be refined. BorTec with its EKABOR® produces a suitable boronizing agent for all requirements. The boriding procedure is especially suitable for unalloyed and low alloyed steels. With increasing content of alloying elements, the diffusion rate and thus the thickness of the achievable boride layer decreases. At the same time, alloying elements such as nickel and chromium contribute to an increase in the hardness and wear resistance.
The range of borideable materials is varied, ranging from cast iron, cast steel, and most steel grades to nickel-based alloys and special materials such as Stellite. A restriction is constituted by materials containing silicon and aluminum. Steels with correspondingly high levels of the elements mentioned can affect the boriding result.
Many properties can be improved by boriding. Thus, boronized surfaces are extremely hard and have a much longer service life compared to functional surfaces such as can be achieved, for example, by nitriding, carburizing, chrome plating, thermal spraying, CVD or PVD coating.
The increased resistance to abrasive wear is accompanied by an improved resistance to cavitation. The reduced friction coefficient of boronized surfaces improves the lubricating properties and reduces wear. In the event of a lubricating film break, the boride layer provides excellent emergency running properties, even at high temperatures up to 1000 °C.
In addition to improving the wear protection of components by boriding, the positive strength characteristics of the base material can be re-established in connection with a subsequent vacuum heat treatment.
The outstanding properties of Borocoat® diffusion layers open the possibility of tempering or aging workpieces after boriding.
Borocoat® diffusion layers are widely used in various industries. Main applications are fittings, power plant technology, gear and transmission technology, textile machinery, pump construction, milling and crushing technology, oil/gas industry, extrusion technique, turbo-charging, agricultural machinery and power tools.
Borocoat® diffusion layers are more wear resistant than nitriding, hard chromium coatings, case hardening layers, thermal spray coatings and PVD coatings.
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