Wear properties of Fe3Al-based HVOF coatings strengthened with in-situ precipitated nitride and boride particles

Iron aluminide coatings reinforced with in-situ precipitated TiN, TiB2 and Fe2B particles were synthesized from Fe3Al, BN and Ti powders using a combination of high-energy ball milling and high velocity oxy-fuel (HVOF) process. In the present work, we investigate the effect of the BN/Ti contents on the microstructure and characteristics of the HVOF coatings and we discuss their tribological properties. The microstructure and composition of powders and coatings were investigated using X-ray diffraction, differential thermal analysis and optical and scanning electron microscopies. The wear rate was evaluated by tribometry in a pin-on-disc configuration, and the mechanical properties were obtained using indentations. X-ray analysis of the coatings prepared from the as-milled powders revealed evidence of TiN, TiB2 and Fe2B peaks. The microhardness (4.3 GPa) and the wear resistance (3 × 10− 4 mm3/Nm) of the coating prepared from the pure Fe3Al powder were increased 3.3 times and by about three orders of magnitude, respectively, when 70 wt% of Fe3Al was milled with 10 wt% of BN and 20 wt% of Ti. Fatigue and abrasive wear were found to be the predominant degradation mechanisms during sliding against an alumina ball of the pure Fe3Al and composite HVOF coatings, respectively. Adhesive wear also contributed to the material loss as confirmed by EDS analysis that revealed a transfer of the coating material to the counterpart.