Research on Properties and Growth Kinetics of Boride Layer of Fe-Based Powder Metallurgy Material Boriding Strengthened with Rare Earth

The Fe-based powder metallurgy material was directly sintered and boriding with CeO2 respectively by a pack powder boriding method to obtain a specimen with a boride layer. Boriding treatment was performed at 1123–1323 K for 3–10 h. The morphology and the thickness of the boride layer were observed with a ultra-depth-of-field microscope and a scanning electron microscope (SEM). The phase composition of the boride layer was analyzed by X-ray diffractometer. The quality of the bonding strength between the boride layer and the substrate was evaluated by the Rockwell-C adhesion test. The results showed that boriding with 2 wt% CeO2 will inhibit the boriding treatment at low temperature and promote it at high temperature. Boriding with 4 wt% CeO2 will inhibits the boriding process at both low and high temperature, and the inhibition becomes stronger as the temperature increases, the inhibiting effect at 1323 K is 9 times that at 1123 K. The quality of the bonding strength of the boride layer with CeO2 is better than that specimen without CeO2 and the quality of the bonding strength with 2 wt% CeO2 is approved by the HF3 grade according to the specifications.