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On the Nitrogen-Induced Lattice Expansion of a Non-stainless Austenitic Steel, Invar 36 ® , Under Triode Plasma Nitriding
Metallurgical and Materials Transactions A ( IF 2.2 ) Pub Date : 2019-11-11 , DOI: 10.1007/s11661-019-05526-0
Xiao Tao , Allan Matthews , Adrian Leyland

Abstract

Chromium, as a strong nitride-forming element, is widely regarded to be an “essential” ingredient for the formation of a nitrogen-expanded lattice in thermochemical nitrogen diffusion treatments of austenitic (stainless) steels. In this article, a proprietary “chrome-free” austenitic iron-nickel alloy, Invar® 36 (Fe-36Ni, in wt pct), is characterized after triode plasma nitriding (TPN) treatments at 400 °C to 450 °C and compared with a “stainless” austenitic counterpart RA 330® (Fe-19Cr-35Ni, in wt pct) treated under equivalent nitriding conditions. Cr does indeed appear to play a pivotal role in colossal nitrogen supersaturation (and hence anisotropic lattice expansion and superior surface hardening) of austenitic steel under low-temperature (≤ 450 °C) nitrogen diffusion. Nevertheless, this work reveals that nitrogen-induced lattice expansion occurs below the nitride-containing surface layer in Invar 36 alloy after TPN treatment, implying that Cr is not a necessity for the nitrogen-interstitial induced lattice expansion phenomenon to occur, also suggesting another type of γN.



中文翻译:

三极管等离子体渗氮下非不锈钢奥氏体Invar 36®的氮诱导晶格膨胀

抽象的

铬是一种很强的氮化物形成元素,被广泛认为是奥氏体(不锈钢)钢热化学氮扩散处理中形成氮膨胀晶格的“必不可少”成分。在本文中,一个专有的“无铬”奥氏体铁-镍合金,因瓦®在400℃下36(FE-36Ni,在重%),其特征在于三极管等离子体氮化(TPN)后处理,以450℃和比较以“不锈”奥氏体对口RA 330 ®(Fe-19Cr-35Ni,wt wtt)在等效氮化条件下处理。在低温(≤450°C)的氮扩散下,Cr确实确实在奥氏体钢的巨大氮过饱和(因此各向异性晶格膨胀和优异的表面硬化)中起着关键作用。然而,这项工作表明,在TPN处理后,Invar 36合金中的含氮化物表面层下方会发生氮诱导的晶格膨胀,这意味着Cr并不是发生氮间隙诱导晶格膨胀现象的必要条件,这也暗示了另一种类型的γ ñ

更新日期:2019-12-21
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