Nickel alloys, properties

Tables 10 and 11 list typical compositions of cast and wrought cobalt-base alloys, respectively. Stress—mpture properties of two wrought cobalt alloys, Haynes 188 and L-605, are compared to those of iron—nickel alloys ia Figure 10 (49). The cobalt alloys generally are inferior ia strength to the strongest cast nickel-base superaHoys. Tensile strengths at low and iatermediate temperatures are particularly deficient for the cobalt alloys.

Eabrication techniques must take into account the metallurgical properties of the metals to be joined and the possibiUty of undesirable diffusion at the interface during hot forming, heat treating, and welding. Compatible alloys, ie, those that do not form intermetaUic compounds upon alloying, eg, nickel and nickel alloys (qv), copper and copper alloys (qv), and stainless steel alloys clad to steel, may be treated by the traditional techniques developed for clads produced by other processes. On the other hand, incompatible combinations, eg, titanium, zirconium, or aluminum to steel, require special techniques designed to limit the production at the interface of undesirable intermetaUics which would jeopardize bond ductihty. 

Fig. 4. Torsion properties versus temperature for the nickel alloys (— —) Nknonic 115 and (-------) Nknonic 90 and for (—) 0.48% C steel (2). To convert...

Table 7. Properties of Cast and Wrought Beryllium Nickel Alloys ...

Table 21. Conductivity and H04 (Hard) Temper Tensile Properties of Cupro—Nickel Alloys...

C725, a 9 wt % nickel alloy that is further strengthened by 2 wt % tin, is used in electrical connectors and bellows. Properties are summari2ed in Table 21. The alloy has good resistance to stress relaxation at room and moderately elevated temperatures, which accounts for its use in connectors and electrical circuit wire wrap pins. 

Properties of copper—nickel alloys are Hsted in Table 14. The alloys in the copper—nickel group have been successfully cast using the centrifugal, investment, permanent, and sand molding methods. The minimum tensile strengths on test bars cast in sand molds are 207—310 MPa (30,000—45,000 psi). 

Table 14. Properties of Copper-Nickel Alloys and Leaded Nickel Bronze and Brass...

Figure 20.6 shows how this evolutionary process has resulted in a continual improvement of creep properties of nickel alloys over the last 30 years, and shows how... 

One must consider, too, the cost of the materials themselves. Some of the metals used in conventional nickel alloys - such as hafnium - are hideously expensive (at UK 100,000 tonne or US 150,000 tonne ) and extremely scarce and the use of greater and greater quantities of exotic materials in an attempt to improve the creep properties will drive the cost of blades up. But expensive though it is, the cost of the... 

Because oxides are usually quite brittle at the temperatures encountered on a turbine blade surface, they can crack, especially when the temperature of the blade changes and differential thermal contraction and expansion stresses are set up between alloy and oxide. These can act as ideal nucleation centres for thermal fatigue cracks and, because oxide layers in nickel alloys are stuck well to the underlying alloy (they would be useless if they were not), the crack can spread into the alloy itself (Fig. 22.3). The properties of the oxide film are thus very important in affecting the fatigue properties of the whole component. 

Nickel alloys have two main properties good resistance to corrosion and high-temperature strength. There are alloys for medium-and low-temperature applications and for high-temperature conditions in which creep resistance is of main importance [24]. 

The cupro-nickel alloys (5-30% of nickel) are perhaps the best of all for strength and resistance to corrosion. Table 3.20 gives typical properties. 

Table 3.20. Mechanical Properties of Annealed Cupro-Nickel Alloys [30]...

Zinc, aluminum, nickel alloys, cobalt alloys and tungsten carbide are applied for sprayed coatings, which are slightly porous. Flame-sprayed zinc coatings are used for corrosion protection of steel and provide similar properties for galvanized coatings. 

Mechanical properties of aimealed cupro-nickel alloys. 83... 

Copper/nickel alloys Alloys containing 5-30% Ni, used mostly in the wrought condition have a very good combination of properties. For optimum corrosion resistance, additions of 0-5-2 0% each of Fe and Mn are made. 

In addition to nickel alloys, nickel also forms an important alloying element in stainless steels and in cast irons, in both of which it confers additional corrosion resistance and improved mechanical and engineering properties, and in Fe-Ni alloys for obtaining controlled physical and magnetic properties (see Chapter 3). With non-ferrous metals nickel also forms important types of alloys, especially with copper, i.e. cupro-nickels and nickel silvers these are dealt with in Section 4.2. 

Table 4.22 Physical properties of corrosion-resistant nickel alloys...

During recent years a considerable amount of information has been published on the anodic behaviour of nickel alloys. The data include studies both of binary alloy systems in which nickel forms the major alloying component and of more complex commercially produced nickel alloys. The data are sufficiently numerous to permit a rational and fairly complete interpretation of many of the corrosion-resistant properties of nickel alloys on the basis of their anodic behaviour. 

Nickel and nickel alloys possess good resistance to sea-water in conditions where the protective properties of the passive film are fully maintained. As pointed out above, Ni-30 Cu Alloy 400, in contrast to its behaviour in acidic solution, normally forms a protective film in neutral and alkaline environments, including sea-water this alloy and its age hardening variant... 

Significant improvement of tantalum powder properties was achieved by the application of molten alkali halides as solvents for potassium heptafluorotantalate, K2TaF7. Variation of the initial concentration of K2TaF7 in the melt, stirring and rate of sodium loading enable a well-controllable production of tantalum powder with a wide variety of specific charges. Heller and Martin [590] proposed the use of a reactor equipped with a stirrer in 1960. Fig. 142 shows a typical scheme of the reactor [24, 576]. All metal parts of the reactor are made of nickel or nickel alloy. 

This review aims to present an account of the catalytic properties of palladium and nickel hydrides as compared with the metals themselves (or their a-phase solid solutions with hydrogen). The palladium or nickel alloys with the group lb metals, known to form /8-phase hydrides, will be included. Any attempts at commenting on the conclusions derived from experimental work by invoking the electronic structure of the systems studied will of necessity be limited by our as yet inadequate knowledge concerning the electronic structure of the singular alloys, which the hydrides undoubtedly are. 

All the nickel alloys are readily fabricated and welded. Their design strengths allow use to elevated temperatures and with relatively thin wall thicknesses. The Nickel Institute (http7Avww.nickelinstitute.org) has excellent publications available that detail the properties and fabrication requirements for both stainless steels and nickel-based alloys, as does SSINA (http //www.ssina.com) and so do many of the manufacturers of these alloys. 

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