Interaction of Titanium Diboride with Iron and AISI 321H Stainless Steel

The interaction of titanium diboride with iron and Kh18N10T iron alloy (equivalent to AISI 321H) in the temperature range 1200–1850°C was studied. No solid-state interaction was found at the contact interface. In the high-temperature range, the interaction proceeds according to the contact melting mechanism, which is characteristic of eutectic systems. Contact melting in the iron–titanium diboride system occurs at ~1400°C and in the 321H–diboride system at ~1340°C. The resultant liquid phase wets the diboride surface with a contact angle of ~40°. When temperature increases to 1450°C, the contact angle does not change and the droplet does not spread over the surface. Study of the alloys showed that the eutectic was found at point 9 ± 2 wt.% TiB₂ for the Fe–TiB₂ system and 6–7 wt.% TiB₂ for the 321H–TiB₂ system. The phase composition of the eutectic depends on the titanium diboride amount in the alloy. In the Fe–TiB₂ system, the crystallized alloy retains the original phase composition (Fe, TiB₂) but has a hypoeutectic, hypereutectic, or eutectic structure. At high TiB₂ content, titanium diboride that did not participate in the interaction was identified in the alloy. In the 321H–TiB₂ alloys, in addition to the main components (stainless steel and titanium diboride), small amounts of TiC and σ-phase (Cr_0.56Fe_0.46), resulting from stainless steel decomposition, were found. The experimental data indicate that iron in contact with titanium diboride can operate up to 1400°C and 321H iron alloy up to 1300°C. Iron and its alloys are promising matrix materials for composites in which pure iron or iron alloys are a metallic matrix and titanium diboride is a hard and wear-resistant component.