Metallurgical aspects of diffusion boriding of tool steels

Jurči Peter - Slovak University of Technology in Trnava (Slovak Republik)

The boronizing is a thermochemical process in which the boron atoms are introduced into the steel surfaces by thermodiffusion. As a result, hard, wear- and corrosion-resistant iron borides layers are formed. In addition, the metallic borides such as chromium borides are formed inside the FeB and Fe2B layers in high alloy steels. Other consequences of increased amounts of carbon and alloying elements are the following: reduced thickness of boride layers, smoother interface between borides and substrate (loss of typical saw-tooth morphology), increased population of carbides in transition zones beneath the compact boride layers, maintaining of strong carbide-forming elements in carbides, which are surrounded by growing borides, and considerable redistribution of minor alloying elements. The current paper deals with possible sources of mentioned microstructural variations as well as changes in elemental contents in boronized and adjacent areas. To demonstrate and discuss this, steels with different carbon- and alloying elements contents are used as examples.

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