PROPERTIES OF COATED REFRACTORY METALS
A review is presented of the information generated since the middle of 1981 on the chemical, physical, and mechanical properties of refractory metals that are coated with oxidation-resistant coatings of advanced-experimental or commercial sthtus. It is a supplement to DMIC Report 162, Coatings for the Protection of Refractory Metals from Oxidation,'' dated November 24, 1961. Recent data on speciflc silicide- and aluminide-type coatings for niobium, molybdenum, thntalum, and tungsten and their alloys reflect general advances in coating quality and performance, understanding of the behavior of coated systems, and more complete realization of the problems associated with the use of coated hardware. Programs to provide comparative evaluations of coatings on niobium and molybdenum alloys have pointed up some of the relative merits and deficiencies of the various coatings. Properties that have been studied and evaluated in recent investigations bave included the following: (1) oxidation lives at various temperatures and pressures, (2) degradation in low-temperature ductility of substrates by coatings or coating processes, (3) degradation of mechanical properties by oxidation exposure (thermal sthbility) (4) effects of strain at low and high temperatures on protectiveness of coatings, (5) stress rupture and creep dath of coated systems, (6) fatigue properties of coated systems, and (7) emittance of coatings. Although there is no ideal'' coating for a given application, the dath now available may permit selection of a coating or coatings based on a balance of performance features such as those listed above. Continued detailed evaluation and general comparative programs are expected to greatiy improve the ability to select a coatingsubstrate system best suited for given design requirements. Generally, the areas involving coated tantalum and tungsten alloy substrates are not so well developed; there are fewer coatings available and data are more limited. (auth)
- Research Organization:
- Battelle Memorial Inst. Defense Metals Information Center, Columbus, Ohio
- NSA Number:
- NSA-18-020452
- OSTI ID:
- 4015744
- Report Number(s):
- DMIC-195; AD-433782
- Country of Publication:
- United States
- Language:
- English
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