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Basic Materials Engineering
Published in David A. Hansen, Robert B. Puyear, Materials Selection for Hydrocarbon and Chemical Plants, 2017
David A. Hansen, Robert B. Puyear
The major difficulty with conventional austenitic stainless steels is that they are susceptible to chloride stress corrosion cracking. In many cases, the risk of chloride stress corrosion cracking is too large to permit the use of an ordinary austenitic stainless steel. In such cases, the following specialty alloys are usually selected: Ferritic stainless steels such as Type 430 SS; note that such materials are subject to chloride pitting. Accordingly, they are selected only for services in which the risk of such pitting is low, for example, clean, flowing saline waters. Alternatively, superferritic grades may be selected.Ni-Cu alloys such as Alloy 400 (67Ni-30Cu; UNS N04400).“Superaustenitic” alloys; these are austenitic alloys with high chromium and nickel, as well as 2-6 wt. percent molybdenum. Alloy AL-6XN (21Cr-25Ni-6.5Mo-N; UNS N08367) is an example of a superaustenitic stainless steel.Nickel alloys such as Alloy 825 (22Cr-42Ni-3Mo, Ti stabilized; UNS N08825).Duplex austenitic-ferritic alloys such as Alloy 2205 (22Cr-5Ni-3Mo-N; UNS S31803).
An investigation on machinability assessment of Al-6XN and AISI 316 alloys: an assessment study of machining
Published in Machining Science and Technology, 2019
Mohanad Alabdullah, Ashwin Polishetty, Junior Nomani, Guy Littlefair
In general, normal and feed forces were higher for the AL-6XN alloy (Figure 9). Factors such as tool wear (which was explained above), alloying elements and strength of the material all raise the measured forces. It was reported by Kalpakjian and Schmid (2016) and Trent (1989) that 2% molybdenum acting as an alloying element in the 316 alloy results in an increase in alloy strength, which elevates the feed forces during machining. In the AL-6XN alloy, the molybdenum is present at higher value, up to 6%, which is also a factor elevating the strength of the alloy and increasing the feed forces. The AL-6XN alloy is characterized by added Nitrogen in its composition. From literature, researchers such as Youssef (2015), Kearns (1985), Painkra et al. (2014) and Sedriks (1989) proved that the presence of Nitrogen increases alloy strength and thus increases the feed forces by motivating the work-hardening tendency during the machining process.