Interaction of titanium diboride with iron and stainless steel AISI 321H

Abstract

The interaction of titanium diboride with iron and its alloy Kh18N10T (equivalent to AISI 321H) in the temperature range 1200–1850 ºC was studied. No solid-phase interaction was found at the contact interface. In the high-temperature range, the interaction process proceeds according to the contact melting mechanism, which is characteristic of eutectic systems. Contact melting in an iron–diboride pair occurs at a temperature of 1400 °C and in a 321Н–diboride pair at 1340 °C. The resulting 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. The study of the alloys showed that the eutectic was found at points 9 ± 2 wt.% TiB₂ for the Fe–TiB₂ system and at 6–7 wt.% TiB₂ for the 321Н–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 remains with the original phase composition (Fe, TiB₂) but already in the form of a hypoeutectic, hypereutectic, or eutectic structure. At high ТіВ₂ content, titanium diboride was found that did not particulate in the interaction was found in the structure. In the 321Н–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)—stainless steel decomposition products—were found in the structure. The experimental data indicate that iron in contact with titanium diboride can operate up to 1400 °С and iron alloy 321Н up to 1300 °С. Iron and its alloys are promising as a matrix in composite materials where pure iron or iron alloys are a metallic matrix and titanium diboride is a hard and wear-resistant component.