THE WORLD'S HOTTEST ALLOYS. PARTS I AND II

Journal Article · Thu Jan 01 00:00:00 EST 1959 · Ind. Research Mag.

OSTI ID:4161415

Goodwin, H B

Some properties of the stable elements which have melting points above 3000 deg F are presented. These include molybdenum, tantalum, riobium, rherium, chromium, the platinum group, chromium, and metal-- ceramic composites, These "scarce" metals are found to exist in the earth's crust sometimes more than the more "conamon" metals, such as copper, lead, etc. Where copper and lead are found to exist in deposits, the "scarce" metals are found to exist as complexes and are scattered throughout the earth's crust, The most promising of these are niobium, molybdenum, tantalum, and tungsten. A molybdenum wire when heated above 2000 deg F will oxidize visually, but when it is coated with its disilicide it does not oxidize appreciably. A niobium--45% zirconium-5% titanium alloy was recently developed which is stated to be both oxidation resistant and fabricable. A combination of alloying and coating may be the best solution to the oxidation problem, with alloying serving to prevent coating defects from becoming catastrophic failures. Rhenium may find use in rheriummolybdenum and tungsten-- rherium/tungsten alloy thermocouples, which are said to be good to 3200 and 4000 deg F, respectively. Chromium-base alloys almost certainly will be oxidation resistant, and no protective coatings will be required. It is expected that their practical temperature limit will be far below the limits for the other metals discussed. Of the platinum group metals, rhodium appears to ep the most oxidation resistant and also has excellent hightemperature strength. The chrome-- alumina and nickel or cobalt-bonded titanium carbide type of cermets seems best because of the excellent bond developed between the metal and ceramic in these systems. Such a bond appears essential for a good cermet. Their fracture strengths are of the same order as those of the better all-ceramic materials. In a composite structure, the ductile component is placed where ductility is required and the brittle component where it is not required. Metal is placed in areas subjected to tension and ceramics in those parts which are lightly stressed or subjected to compressive stresses. There is considerable optimism that true ceramics with greatly improved toughness and perhaps even a little ductility can be developed eventually. (B.O.G.)

• Research Organization: Battelle Memorial Inst., Columbus, Ohio
• NSA Number: NSA-14-009789
• OSTI ID: 4161415
• Journal Information: Ind. Research Mag., Vol. Vol: 1, Nos. 3 and 4; Other Information: Orig. Receipt Date: 31-DEC-60
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

METALS, CERAMICS, AND MATERIALS
ALUMINUM OXIDES
BONDING
BRITTLENESS
CERAMICS
CERMETS
CHROMIUM
CHROMIUM ALLOYS
COATING
COBALT
COMPLEXES
COPPER
CORROSION PROTECTION
DEFECTS
DEPOSITS
DUCTILITY
EARTH
EARTH CRUST
EFFICIENCY
FABRICATION
FAILURES
HEATING
HIGH TEMPERATURE
LEAD
MELTING POINTS
METALS
MOLYBDENUM
MOLYBDENUM COMPOUNDS
NICKEL
NIOBIUM
NIOBIUM ALLOYS
OXIDATION
PLANNING
PLATINUM
PRESSURE
RHENIUM
RHENIUM ALLOYS
RHODIUM
SILICIDES
STABILITY
STRESSES
TANTALUM
TENSILE PROPERTIES
THERMOCOUPLES
TITANIUM ALLOYS
TITANIUM CARBIDES
TUNGSTEN
TUNGSTEN ALLOYS
WIRES
ZIRCONIUM ALLOYS