Microstructural and tribological characterization of niobium boride coating produced on AISI 1020 steel via multicomponent boriding

Niobium boride coating was produced on AISI 1020 steel by multicomponent boriding process. Boriding treatment at 1000 degrees C for 4 h was followed by thermo-reactive diffusion technique at 1000 degrees C for 6 h under argon atmosphere. Microabrasive wear tests were carried out using SiC abrasive particles at slurry concentrations of 0.5 and 1.0 g cm(-3). Normal loads of 0.49 and 0.98 N were used. NbB and Nb5B6 phases were identified by XRD analysis. The niobium boride coating thickness was 2.0 +/- 0.5 mu m and its hardness was 1360 +/- 200 HK0.01. Owing to the presence of a porous region on the niobium/iron boride layers the abrasive wear resistance decreased comparing to the borided and untreated AISI 1020 steel. Rolling abrasion was the main wear mechanism observed.