Low-temperature boriding of high-carbon steel

Boriding has attracted great interests in improving mechanical performance of materials. The high processing temperature and the relatively thin boride layer, however, have limited its applications. Here we report a method to boronize high-carbon steels at a relatively low temperature (780 °C). Using the arc melting process, a thick (> 400 μm) boronized coating is obtained. Two iron-boride phases (FeB and Fe2B) coexist in the borided layer. The surface hardness of the steel is increased by ~ 57%, while the friction is reduced by ~ 17% and ~ 65% under steel-steel and steel-diamond contacts, respectively. In a 40,000 cycle wear test, the wear track on the steel surface becomes invisible after the boriding treatment. The low-temperature process developed in this study is applicable to other materials and is effective in making thick boride coatings with less energy consumption.