Alloys chromium

TABLE 11.57 Type E Thermocouples Nickel-Chromium Alloy vs. Copper-Nickel Alloy Thermoelectric voltage in millivolts reference junction at 0°C. 

At higher temperatures. Monel, a nickel—copper alloy, is suitable, as is HasteUoy-C, a nickel molybdenum—chromium alloy. 

Because of its position in the Periodic Table, molybdenum has sometimes been linked to chromium (see Chromiumand chromium alloys) or to other heavy metals. However, unlike those elements, molybdenum and its compounds have relatively low toxicity, as shown in Table 3. On the other hand, molybdenum has been identified as a micronutrient essential to plant life (11,12) (see Fertilizers), and plays a principal biochemical role in animal health as a constituent of several important enzyme systems (see Mineral nutrients). 

Ferritic Stainless Steels. These steels are iron—chromium alloys not hardenable by heat treatment. In alloys having 17% chromium or more, an insidious embrittlement occurs in extended service around 475°C. This can be mitigated to some degree but not eliminated. They commonly include Types 405, 409, 430, 430F, and 446 (see Table 4) newer grades are 434, 436, 439, and 442. 

Berylha ceramic parts ate frequendy used in electronic and microelectronic apphcations requiting thermal dissipation (see Ceramics as ELECTRICAL materials). Berylha substrates are commonly metallized using refractory metallizations such as molybdenum—manganese or using evaporated films of chromium, titanium, and nickel—chromium alloys. Semiconductor devices and integrated circuits (qv) can be bonded by such metallization for removal of heat. 

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