A study on RE Boronizing Process in a Titanium Alloy

In this study, the function of rare earth (RE) oxides added in boronizing agents was studied by analyzing not only the boronized titanium (Ti6Al4V) but also the agent materials at 900–1050 °C. XRD results showed that low-melting-point RE borates were formed in the boronizing processes. The existence of the RE borates probably provided a partially liquid boronizing environment for the titanium alloys. By scaling up the boronizing process for larger samples, not only borides but also carbides were formed on the samples indicating a borocarburizing process occurring. The boronized alloys showed excellent mechanical properties (Vickers hardness 1800HV0.1, Rockwell hardness 95–98 HR15Y up to 900 °C, tensile strength 941 MPa, fiction coefficient 0.15, friction bonding strength >300 N) and a good burner rig thermal shock performance (without spallation of surface oxide).