【作者】 李长胜；

【导师】 戴起勋；

【作者基本信息】 江苏大学 ， 材料学， 2007， 硕士

【摘要】 本文以24Mn-13Cr-0.44N、24Mn-18Cr-3Ni-0.62N和1Cr18Ni9Ti三种奥氏体不锈钢为研究对象，研究了24Mn-18Cr-3Ni-0.62N在室温下的拉伸性能，该新型奥氏体不锈钢拉伸时没有明显的屈服平台，力学性能为：σ_0.2=525MPa，σ_b=890MPa，δ=41％，φ=57％，n=0.421，具有很高的强度和优良的塑性，拉伸时形成的滑移带粗大、密集，若金相截面和某（111），面平行或接近平行，还可发现具有正三角形的形变组织，拉伸断口为韧性断口，块状夹杂物为裂纹发源地之一，净化材料可以进一步提高材料的抗拉强度。同时，本文重点研究了两种高氮奥氏体不锈钢的磨粒磨损性能，并与18-8型奥氏体不锈钢作了对比探讨其磨粒磨损机理。试验结果表明，在三个低载荷下，18-8型不锈钢随载荷的增加，磨损量急剧上升，而两种高氮的奥氏体不锈钢受载荷的影响比较小。此外，磨粒的形状和粒度对材料耐磨性也有重要影响，在同样载荷下，在粗砂时要比细砂时磨损量大。磨损前期主要是磨粒磨损，最明显的特征是“犁沟”，后期以粘着磨损为主。接下来以粘着和剥落机制为主，剥落区内有部分犁沟痕迹，还有少量的微裂纹。随着载荷的增加，磨粒磨损加剧了，并且粘着磨损也提前了，出现了磨粒磨损和粘着磨损明显的交互作用。在磨损过程中，18-8型奥氏体不锈钢亚表层发生了ε马氏体相变，而两种含氮的奥氏体不锈钢很少或几乎没有ε马氏体出现，但出现了大量的位错和形变孪晶。在对磨损剖面形变层的硬度进行测试时发现，普通的不锈钢由于发生了马氏体相变，硬度增加明显，而两种含氮奥氏体不锈钢几乎没有发生马氏体相变，硬度增加不是很多，即在低载荷下，加工硬化不足。一个可能的结论是：此新型奥氏体不锈钢正如高锰钢一样，在高载荷下，它的耐磨性才表现得更为突出。此外，本文还研究了三种奥氏体不锈钢的耐点腐蚀性能。结果发现，两种含氮奥氏体不锈钢的耐点腐蚀性能均比18-8型奥氏体不锈钢好。不管是室温还是高温，普通不锈钢的点蚀数目明显比两种高氮奥氏体不锈钢要多，在50℃高温下，我们在24Mn13Cr0.44N高氮奥氏体钢的点蚀形貌中发现具有正三角形的结构，这就是奥氏体（111）_γ面。表明，温度升高时，含氮奥氏体不锈钢可能会优先在奥氏体的滑移面（111）_γ面发生点蚀。我们知道，不锈钢中夹杂物是重要的点蚀源之一。由于此新型奥氏体不锈钢锰含量比较高，夹杂物较多，因此，净化材料可以进一步提高此类奥氏体不锈钢的耐点腐蚀性能。更多还原

【Abstract】 24Mn-13Cr-0．44N、24Mn-18Cr-3Ni-0．62N、1Cr18Ni9Ti-three kinds of austenitic stainless steels-were studied in this paper. Tensile properties of a new type austenitic stainless steel 24Mn-18Cr-3Ni-0．62N at room temperature were investigated. During tensile the austenitic stainless steel has not obvious yield point elongation. Tensile property parameters are:σ=525MPa,σ=890MPa,δ=41%, (?)=57%, n=0．421．It possesses very high strength and excellent plasticity. Slip bands formed were coarse and dense, regular triangle deformation microstructure can be founded if optical microscopy section is parallel or approximately parallel to (111) plane.The fracture is toughness fracture . The inclusions are one of crack headstream, and purifying materials can further enhance tensile strength of materials.At the same time, abrasive wear properties of high nitrogen austenitic stainless steel under different loads were investigated in this paper, and compared with that of 18-8 austenitic stainless steel .The mechanism of abrasive wear was discussed. Under the three low loads , wear loss of 18-8 stainless steels is sharply increased with increasing of loads, but the influence of load on two kinds of high nitrogen austenitic stainless steel is smaller. Besides, shape and size of abrasive particles have an important effect on resistance to wear of materials. Under the same load, wear loss of coarse sands is more than that of fine sands. The earier stage of wear is mainly abrasive wear, and the most obvious feature is furrow. The advanced stage of wear is mainly adhesive wear. Then main wear mechanism is adhesion and flake, and there are part ploughing trace and a small quality of microcrack. With increasing of loads, abrasive wear is aggravating , adhesive wear advances and appears interaction between abrasive wear and adhesive wear. During wear, 18-8 austenitic stainless steel causeεmartensite transformation in the subsurface stratum, while two kinds of nitrogen-containing austenitic stainless steel few or almost not causeεmartensite transformation, instead appears large numbers of dislocations and deformation twins. The microhardness of wear profile was tested, it is found that hardness of common austenitic stainless steel increases obviously, but that of new type austenitic stainless steel increases less evidently. That is to say, work-hardening of nitrogen-containing austenitic stainless steel is not enough. One possible conclusion is : Just as high manganese steel, wear-resistance of the new type austenitic stainless steel performances more obviously under high loads.Furthermore, resistance to pitting corrosion properties of three kinds of austenitic stainless steel was studied. The results show that resistance to pitting corrosion of two kinds of nitrogen-containing austenitic stainless steel are better than that of 18-8 austenitic stainless steel. The number of nitrogen-containing austenitic stainless steel is less than that of 18-8 austenitic stainless steel at room temperature and high temperature. It is founded that pitting corrosion pattern of high nitrogen austenitic stainless steel 24Mn-13Cr-0．44N possesses regular triangle structure At high temperature of 50 degree centigrade, which is austenitic (111) plane. It is showed that nitrogen-containing austenitic stainless steel possibly happen pitting corrosion firstly in austenitic slip plane (111) when the temperature rises. The content of manganese of the new type austenitic stainless steel is very high and the inclusions are much more, so purifying materials can further enhance resistance to pitting corrosion properties of the new type austenitic stainless steels.更多还原