Mechanical properties after corrosion

Fig. 8.23 Effect of tempering on the mechanical properties and corrosion resistance of type 420 stainless steel (after Sedriks )...

X, Y, and Z directions. Orthogonally woven structures offer superior mechanical properties and corrosion resistance after infusing resin into a composite. The panel, as shown in Figure 9.25, has 61 layers of warp, 62 layers of fill, and Z fibers. The typical fiber volume of the panel is around 55%, and X, Y, and Z fiber volume fractions are around 40%, 40%, and 20%, respectively. The typical Z fiber volume fraction can vary from 3% to 33%, depending on the performance requirements of the end use. 

Due to the high chromium contents, duplex alloys are sensitive to 885 (475°C) embrittlement. This generally limits their usage to 600°F (SIS C) maximum for pressure vessels. Due to the presence of nickel, chromium, and molybdenum they are also susceptible to the formation of affect mechanical properties and corrosion resistance due to alloy depletion. The temperature range of 1100°F (593 C)-1600°F (882°C) and most rapidly at about 1450°F (788°C). The deleterious effects of phase formation are not obvious at the elevated temperature but can become a factor at room temperature. The formation of a phase in these alloys is sufficiently rapid to have an effect on properties due to slow cooling (air) after anneal. A measurable effect as a result of exposure in this temperature range due to welding has been demonstrated. 

Monel, the classic nickel-copper alloy with the metals in the ratio 2 1, is probably, after the stainless steels, the most commonly used alloy for chemical plant. It is easily worked and has good mechanical properties up to 500°C. It is more expensive than stainless steel but is not susceptible to stress-corrosion cracking in chloride solutions. Monel has good resistance to dilute mineral acids and can be used in reducing conditions, where the stainless steels would be unsuitable. It may be used for equipment handling, alkalies, organic acids and salts, and sea water. 

Oilfields in the North Sea provide some of the harshest environments for polymers, coupled with a requirement for reliability. Many environmental tests have therefore been performed to demonstrate the fitness-for-purpose of the materials and the products before they are put into service. Of recent examples [33-35], a complete test rig has been set up to test 250-300 mm diameter pipes, made of steel with a polypropylene jacket for thermal insulation and corrosion protection, with a design temperature of 140 °C, internal pressures of up to 50 MPa (500 bar) and a water depth of 350 m (external pressure 3.5 MPa or 35 bar). In the test rig the oil filled pipes are maintained at 140 °C in constantly renewed sea water at a pressure of 30 bar. Tests last for 3 years and after 2 years there have been no significant changes in melt flow index or mechanical properties. A separate programme was established for the selection of materials for the internal sheath of pipelines, whose purpose is to contain the oil and protect the main steel armour windings. Environmental ageing was performed first (immersion in oil, sea water and acid) and followed by mechanical tests as well as specialised tests (rapid gas decompression, methane permeability) related to the application. Creep was measured separately. 

Mechanical and Chemical Stability. The materials must maintain their mechanical properties and their chemical structure, composition, and surface over the course of time and temperature as much as possible. This characteristic relates to the essential reliability characteristic of energy on demand. Initially, commercial systems were derived from materials as they are found in nature. Today, synthetic materials can be produced with long life and excellent stability. When placed in a battery, the reactants or active masses and cell components must be stable over time in the operating environment. In this respect it should be noted that, typically, batteries reach the consumer 9 months after their original assembly. Mechanical and chemical stability limitations arise from reaction with the electrolyte, irreversible phase changes and corrosion, isolation of active materials, and local, poor conductivity of materials in the discharged state, etc. 

Transparent YAG ceramics (yttrium aluminate garnet, Y3AI5O12) have excellent optical and mechanical properties. Besides flieir widespread applications in solid-state lasers, transparent YAG ceramics have also been used as envelopes in lamps [10, 11]. As expected, the corrosion resistance of YAG to rare-earth halide fills was less than that of PCA. For instance, the wall could be attacked by the rare-earth halide fills (Reis), such as Tmis, after a prolonged duration of application, due to the following reaction ... 

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