SURFACE CHARACTERIZATION OF PACK AND PLASMA PASTE BORONIZED OF 21NiCrMo2 STEEL

In the present study, 21nicrmo2 steel were plasma paste boronized by using 100 wt.% b2o3, 70 wt.% b2o3 + 30 wt. % sic, 70 wt.% b2o3 + 30 wt.% b4c, 30 wt. % b2o3 + 70 wt.% sic, 30 wt.% b2o3 + 70 wt.% b4c pastes. this steel ispopular bearing steel and have a widespread use in engineering applications. plasma paste boronizing process was carried out in a dc plasma system at temperature of 700, 750 and 800 °c for 2, 5 and 7 h in a gas mixture of 70%h2 - 30%ar under a constant pressure of 10 mbar. pack boronizing of same steel was also carried out at 700, 750 and 800 °c for 2, 5 and 7 h. the properties of boride layer were evaluated by sem, edx, x-ray diffraction, vickers micro-hardness testing. x-ray diffraction analysis of boride layers on the surface of the boronized steel revealed feb and fe2b. plasma paste boronizing process showed that since the plasma activated the chemical reaction more, a thicker boride layer was formed than conventional boronizing methods at same temperatures. it was possible to form boride layer with the same thickness at lowertemperatures in plasma environment by using b2o3 paste mixture.