High creep

A more extensive comparison of many potential turbine blade materials is available (67). The refractory metals and a ceramic, sHicon nitride, provide a much higher value of 100 h stress—mpture life, normalised by density, than any of the cobalt- or nickel-base aHoys. Several intermetaHics and intermetaUic matrix composites, eg, aHoyed Nb Al and MoSi —SiC composites, also show very high creep resistance at 1100°C (68). Nevertheless, the superaHoys are expected to continue to dominate high temperature aHoy technology for some time. 

Monels Superalloys Ni -r 30 Cu 1 Fe 1 Mn Ni -r 30 Cr 30 Fe 0.5 Ti 0.5 Al Ni -r 10 Co 10 W 9 Cr 5 A1 2 Ti Strong, corrosion resistant heat-exchanger tubes. Creep and oxidation resistant furnace ports. Highly creep resistant turbine blades and discs. 

However, world production is only about 55 000 tonnes per annum and this is a reflection of the high volume cost, the rather specialised techniques involving lengthy processing times and to a smaller extent the high creep rate under load. 

Polyimide It is a high-cost heat and fire resistant plastic, capable of withstanding 500°F (260° C) for long periods and up to 900°F (482° C) for limited periods without oxidation. It is highly creep resistant with good low friction properties. It has a low coefficient of expansion and is difficult to process by conventional means. It is used for critical engineering parts in aerospace, automotive and electronics components subject to high heat, and in corrosive environments. 

The next criterion was the selection of materials that would yield the desired mechanical properties. Butyl elastomer (HR), a copolymer of isobutylene with a small amount of isoprene, has outstanding low-temperature properties and very high damping, but has very high creep without cross-linking." It was theorized that a blend of SIBS TPE and butyl elastomer, filled to achieve the required minimum density of 2.4 g cm, would be a promising composite for less-lethal ammu-... 

Figure 4.61(b) displays the high creep moduli of glass fibre reinforced PA 12 for comparison with the neat PA 12 in Figure 4.61(a). It should be noted that the modulus scale is ten times that of Figure 4.61(a) and, moreover, with five to seven times heavier loads. 

Alteration by moisture exposure is very weak but shrinkage and coefficients of thermal expansion are high creep resistance is low. 

Creep behaviour is good even when the temperature rises. Neat polysulfones have medium moduli that involve medium strains for moderate loading. Consequently, creep moduli are also in a medium range at room temperature but they decrease more slowly than the majority of other thermoplastics when the temperature rises. Reinforcement with fibres leads to high moduli and consequently high creep moduli. 

Mo ) 1.25 CrMo 1 2.25 CrMo ( 6 to 12 CrMoVW) High creep strength for 1. pressure vessels such as boilers operating at elevated temperatures and 2. oil refinery vessels such as crackers and reformers with high hydrogen pressures. 

LX-08 is an extrudable, curable expl developed for use in Dautriche timing tests LX-09 is similar to the LASL expl PBX-9404, but with significantly improved thermal stability and slightly poorer physical props LX-10 is in the same energy class as LX-09 and PBX-9404, but utilizing HMX and Viton A like LX-04, and having excellent thermal characteristics. It also exhibits high creep resistance, but may be somewhat more sensitive... 

Alloy 602 CA a modification of other 600 alloys is used in heat-treating, annealing furnaces, furnace rolls, high-temperature calcination application, catalytic support systems, and glow plugs in automobiles, vitrification of nuclear waste 800, 45 TM Have high creep and rupture strength and oxidation resistance used... 

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