0Cr18Ni9不锈钢表面纳米化组织及其热稳定性对低温渗氮行为的影响  

EFFECT OF SURFACE NANO CRYSTALLIZATION AND THERMAL STABILITY OF 0Cr18Ni9 STAINLESS STEEL ON LOW TEMPERATURE NITRIDING BEHAVIOR

作　　者：葛利玲[1] 卢正欣[1] 井晓天[1] 刘忠良[1] 田娜[1] 

机构地区：[1]西安理工大学材料科学与工程学院,西安710048

出　　处：《金属学报》2009年第5期566-572,共7页Acta Metallurgica Sinica

基　　金：陕西省自然科学基金资助项目2005E_101~~

摘　　要：采用超音速微粒轰击技术(SFPB)对0Cr18Ni9不锈钢试样进行了表面纳米化处理,并对SFPB处理后的试样进行热处理和低温气体渗氮处理,分析讨论了表面纳米化组织及其热稳定性对低温渗氮行为的影响.结果表明:经SFPB处理后,试样表层形成厚约250μm的变形区,表面组织为纳米晶,平均晶粒尺寸为15 nm,其变形机制以孪生为主,变形同时表面发生了马氏体相变,表面硬度明显提高.对SFPB处理的试样经450℃热处理后,纳米晶未发生明显粗化,马氏体量减少很小,硬度保持稳定,因而具有良好的热稳定性.晶粒细化、马氏体相变及其良好的热稳定性有利于实现低温快速渗氮,使渗层厚度明显增加,表层硬度得到进一步提高,硬度分布梯度也得到了改善.The composite structure with a nano crystallized surface and the matrix is very useful to obtain good comprehensive properties. Surface nanocrystallization is an important way to make a good combination of high hardness on the surface and good ductility at the center of materials, which not only modifies the surfacial properties, but also provides more channels to accelerate atoms to diffuse. In this work, a nanostructured layer was fabricated on a 0Crl8Ni9 stainless steel sheet surface by a supersonic fine particle bombarding （SFPB） technique, and followed by low temperature gas nitriding. The effect of the nanocrystallization on the surface of the 0Cr18Ni9 stainless steel on thermal stability and the gas nitriding at low temperature was investigated by metallograph, XRD, TEM and microscopic hardness. It is found that a deformation zone with a depth of about 250 μm is formed on the surface after SFPB treatment. The surface microstructure is composed of nanocrystals with an average grain size of 15 nm. It is also found that twinning dominantly controls surface deformation. Meanwhile, there is martensite transformation on the surface during the deformation, thus resulting in a significant increase of surface hardness. After nitriding at 450 ℃, the SFPB treated specimen shows an excellent thermal stability with a stable hardness even though no obviously coarsening of nanocrystal on the surface layer and a slight decrease of the amount of martensites. In comparison with the specimen without SFPB treatment, grain refinement, martensite transformation and excellent thermal stability are the main reasons favorable for rapid nitriding at low temperature, which contribute to the thicker nitriding layer, the further increase of surface hardness and the improvement of hardness gradient.

关 键 词：0Cr18Ni9不锈钢 表面纳米化 热稳定性 低温气体渗氮 

分 类 号：TG142.71[一般工业技术—材料科学与工程] TG156.8[金属学及工艺—金属材料]