Compound layer growth and compound layer porosity of austenite plasma nitrocarburised non-alloyed steel
Compound layer growth and compound layer porosity of austenite plasma nitrocarburised non-alloyed steel
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DOI：
10.1016/0257-8972(94)01009-8
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发表时间：
1995-03
影响因子：
5.4
通讯作者：
Shi Li;R. Manory;J. Hensler
中科院分区：
文献类型：
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作者：
Shi Li;R. Manory;J. Hensler
通过控制氮、氢和甲烷含量为25%（体积分数）的等离子氮碳共渗气氛，研究了奥氏体等离子氮碳共渗缓冷AISI 1020钢试样的化合物层生长和化合物层孔隙率N2，73.25体积% H2，1.75体积% CH4，600 °C。在等离子氮碳共渗的初始阶段，形成了类似于盐浴氮碳共渗中所观察到的“珊瑚片的开放结构”的高度多孔的表面结构。处理9 min后，形成了由奥氏体、化合物层和氮奥氏体组成的三层结构，并进一步发展为含化合物层和氮奥氏体亚层的ε-氮化铁。气孔主要在晶界、富碳区和α-铁形成处形核长大。还检查了淬火和退火样品的结构。淬火后可保留纯ε化合物顶层。该层在该气体成分下不稳定，并在缓慢冷却过程中转变为含有ε的γ '、α-铁（和Fe 3C）。退火通过使马氏体和残余氮奥氏体转变为贝氏体，提高了普碳钢的心部性能。
Compound layer growth and compound layer porosity of an austenite plasma nitrocarburised slowly cooled AISI 1020 steel sample were studied by controlling the plasma nitrocarburising atmosphere with nitrogen, hydrogen and methane content in the following proportions: 25 vol.% N2, 73.25 vol.% H2, 1.75 vol.% CH4at 600 °C. During the iniial stage of plasma nitrocarburising, highly porous surface structures are formed similar to those described as “the open structure of a piece of coral” observed in salt bath nitrocarburising. For a 9 min treated sample a triple layer composed of cementile, compound layer and nitrogen austenite is formed, which further develops into ε iron nitride containing a compound layer and the dissociated nitrogen austenite sublayer. Porosity is mainly nucleated and grows at the grain boundaries, the carbon-enriched region and places where α-iron forms. The structures of quenched and annealed samples were also examined. Pure ε compound top layer can be retained after quenching. This layer is unstable at this gas composition and transforms to γ′, α-iron (and Fe3C) containing ε during slow cooling. Annealing enhances the core property of the plain carbon steel by transforming the martensite and residual nitrogen austenite into bainite.