REACTION BETWEEN HEAT-RESISTING ALLOYS AND REFRACTORY OXIDES AT HIGH TEMPERATURES IN VACUUM

Journal Article · Fri Jan 01 00:00:00 EST 1960 · Stal'

OSTI ID:4820736

Amonenko, V M; Romanchenko, K G; Tron', A S

In order to investigate the phenomenon of heat resisting alloys that contain elements which enter easily into reaction with the oxides of the refractory crucible and to establish the crucible composition that has least effect on the alloys, tests were undertaken with crucibles containing ZrO/sub 2/, BeO, MgO, Al/sub 2/O/sub 3/, and (Al/sub 2/O/sub 3/ + 1% TiO/sub 2/) and nickelbase heat-resisting alloys at various temperatures and with various holding times in vacuum. The tests were carried out in resistance furnaces having molybdenum heaters, the crucibles were made from chemically pure oxides, having a porosity between 0-2% and which were stabilized with 5% MgO or CaO. In the tests the effect of casting temperatures, duration of vacuum treatment, and crucible material on the gas content of the alloy were investigated. lt was found that crucibles made from Al/sub 2/ O/sub 3/, ZrO/sub 2/, MgO, and BeO entered into reaction with the C of the casting. Al, Zr, and Be reduced from the oxides were dissolved in the metal while carbon oxide and magnesium were eliminated in the gas-phase. The reduction process was accelerated at increased temperature. The minimum reduction rate was observed at l450-l500 f C and the minimum amount of reduction products were found in the alloy when the vacuum process no more than 20-30 minutes. The lowest oxygen content was found in alloys cast in ZrO/sub 2/ and BeO crucibles while the reduction process was the most intensive in MgO crucibles. When casting in Al/sub 2/O/sub 3/containing crucibles, an exchange reaction took place between metal and refractory material, during which chrome and titanium were oxidized and Al/sub 2/O/sub 3/ was reduced to Al/sub 2/O/sub 3/, followed by its decomposition into Al/sub 2/O/sub 3/ and A l. Petrographically it was established that Cr/sub 2/O/sub 3/ was present in tbe refractory substance, indicating a reaction between the crucible and the chrome of the alloy. The tests on inclusions and the microscopic investigations showed spinelides of Mg(Cr,Al)/sub 2/O/sub 4/ in MgO crucibles, which were formed as a result of the reaction between the alloying elements and magnesium oxide. The higher the casting temperature, the longer the holding time of the metal, and the lower the remaining pressure in the chamber, the more complete was the elimination of N and H from the alloy. The refractory materials were arranged according to their degree of resistance against reaction with the alloy in the following series: MgO < Al/sub 2/O/sub 3/; (Al/sub 2/O/sub 3/ + 1% TiO/sub 2/) < BeO < ZrO /sub 2/. (OTS)

• Research Organization: Scientific-Research Inst. of Refractory Materials, Ukrainian SSR
• NSA Number: NSA-16-006756
• OSTI ID: 4820736
• Journal Information: Stal', Vol. Vol: 20: No. 11; Other Information: Orig. Receipt Date: 31-DEC-62
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

METALS, CERAMICS, AND OTHER MATERIALS
ALLOYS
ALUMINUM OXIDES
BERYLLIUM OXIDES
CALCIUM OXIDES
CASTING
CHEMICAL REACTIONS
CHROMIUM OXIDES
CRUCIBLES
GASES
HEAT RESISTING METALS
HIGH TEMPERATURE
HYDROGEN
LATTICES
MAGNESIUM OXIDES
MINERALS
NITROGEN
OXIDES
QUALITATIVE ANALYSIS
SPINELS
TEMPERATURE
TITANIUM OXIDES
VACUUM
ZIRCONIUM OXIDES