超音速微粒轰击AISI52100钢的表层组织与摩擦学性能研究

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	超音速微粒轰击AISI52100钢的表层组织与摩擦学性能研究
	劳远侠
学位类型	博士
导师	熊天英 ; 杜昊
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料加工工程
关键词	超音速微粒轰击 Aisi52100钢表面纳米化显微结构摩擦磨损 Surface Nanocrystallization Supersonic Fine Particle Bombarding (Sfpb) Aisi 52100 Steel Microstructure Wear Resistance
摘要	摘要表面自纳米化技术通过引入强烈塑性变形在金属表面制备一定厚度的纳米晶体层，提高材料的力学、耐腐蚀、耐磨损等性能，被认为是未来最有可能实现工业应用的纳米化技术之一。目前，人们对表面纳米化技术的研究多针对纯金属和退火态钢。而多相合金和淬火态钢在工程材料应用中占有很大比例，研究多相合金的表面纳米化对该技术在工程领域的推广有重要意义。本文选择工程领域应用广泛的轴承钢——AISI52100钢作为研究对象，利用超音速微粒轰击（Supersonic Fine Particles Bombarding, SFPB）技术分别对退火态和淬火态的AISI52100钢进行表面纳米化处理；利用扫描电子显微镜（SEM），接触式表面轮廓仪和显微硬度计研究了不同工艺参数下SFPB处理对该材料表面形貌、组织和性能的影响，并对主要工艺参数进行了优化；利用X-射线衍射（XRD）、扫描电子显微镜(SEM)和透射电镜（TEM）对超音速微粒轰击后样品的表层组织形貌、相结构和相组成进行了表征；利用显微硬度计、非接触式表面形貌仪、XRD、摩擦磨损设备、能谱仪（EDS）、电子探针（EPMA）等对SFPB处理后样品的硬度、残余应力、表面粗糙度和摩擦学性能进行了表征，探索了不同载荷下，SFPB处理的AISI52100钢的干摩擦磨损机制。论文的第一部分工作是对SFPB处理的主要工艺参数进行优化。 SFPB处理AISI52100钢时，选用平均直径30μm的球形氧化铝粉作为轰击微粒。随着载流气体压强的增大，试样表层硬度有所增加。但当压强增大到某一特定值时，试样表面会萌生裂纹和孔洞，导致表面硬度急剧下降。对退火态AISI52100钢来说，最佳压强为1.5MPa；对淬火态AISI52100钢来说，最佳压强为2.0MPa。对退火态试样而言，在最佳压强下，轰击时间越长，试样表面塑性变形层厚越均匀。但当轰击时间超过一定值时，退火试样表面萌生孔洞和微裂纹;对淬火态试样而言，轰击时间延长能在一定程度上增加塑性变形层的厚度。但当轰击时间超过一定值时，试样塑性变形层厚度不会发生明显变化。最佳压强下，退火态试样每平方厘米所需轰击时间为2s；淬火态试样每平方厘米所需轰击时间为0.4s。对淬火态AISI52100钢辊进行SFPB处理时，气体温度会影响钢辊表面粗糙度，粗糙度随气体温度升高而增加。当气体温度为室温时，SFPB处理的钢辊表面粗糙度为1.2μm，此时轧制的钢板质量最好。论文的第二部分工作是对SFPB处理后AISI52100钢的表层组织进行表征。实验研究发现，退火态和淬火态的AISI52100钢表面晶粒均被细化至纳米级，退火态钢的表层晶粒平均尺寸达到20nm，纳米层厚度15μm；淬火态钢的表层晶粒平均尺寸30~60nm；纳米层厚度约5μm。退火态AISI52100钢最表层为纯铁素体纳米晶层，表层发生了渗碳体的分解，次表层发生了渗碳体的变形、细化；淬火态AISI52100钢最表层为纯马氏体纳米晶层，表层发生了马氏体相变和渗碳体的分解。论文的第三部分工作是对SFPB处理后AISI52100钢的摩擦学及相关性能进行研究。实验研究发现，SFPB处理后，钢表面形貌为随机分布球形弹坑。退火态AISI52100钢表面粗糙度为1.9μm，淬火态AISI52100钢的表面粗糙度为1.2μm。对淬火态AISI52100钢辊进行SFPB处理，钢辊表层出现约70μm的残余压应力层。最大残余压应力约745MPa，出现在钢辊表层。SFPB处理后，退火态和淬火态试样表面均出现一层约70μm的硬化层，硬化层是晶粒细化、加工硬化、相变强化共同作用的结果。退火态AISI52100钢的硬度最大值（470HV）出现在表层；淬火态AISI52100钢的硬度最大值（740HV）出现在次表层距表面10μm处。摩擦实验表明，对退火态试样而言，载荷10N时，由于较高表面粗糙度的影响，SFPB处理的试样具有更高的摩擦系数，较差的耐磨性能；在20N~40N载荷下，由于表层硬度更高，SFPB处理的试样具有较低的摩擦系数和更高的耐磨性能。对淬火态AISI52100钢而言，在低载荷15N~25N下，由于更高的表层硬度，SFPB处理的试样有更好耐磨性能；在高载荷50N~75N时，由于试样的磨损机制由严重的氧化磨损所主导，SFPB处理的试样的耐磨性能相比未处理试样提高不大。"
其他摘要	"ABSTRACT Microstructure and Tribology Behavior of AISI52100 Steel after Supersonic Particles Bombarding Treatment Yuanxia Lao( Materials Processing Engineering ) Supervised by Prof. T.Y. Xiong and Associate Prof. H. Du By means of surface nanocrystallization technique a nanostructured layer can be fabricated in the surface of the treated metal. With a nanostructured surface layer, its mechanical property, wear resistance, corrosion resistance etc. can be improved significantly. Surface nanocrystallization technique has been considered to be one of the most promising nano-techniques in the future. By now, most investigations of surface nanocrystallization technique have been focusing on pure metals and annealed steel. Considering the great proportion of polyphase alloys and quenched steel used in the engineering field, an investigation of polyphase alloys and quenched steels is very meaningful for an application of the surface nanocrystallization technique to engineering field. In the work reported in this paper, wildly used AISI52100 steels (in annealed and quenched conditions) have been treated by Supersonic Fine Particles Bombarding(SFPB) treatment to make a nanostructure surface layer. The surface topograph, morphology of the surface layer and microhardness distribution of the surface layer have been investigated by using a surface profiler system, a scanning electron microscopy (SEM) and a microvickers hardness tester. The microstructure, phase composition and residual stress distribution of the surface layer in AISI52100 steel after SFPB treatment have been characterized by means of X-ray diffraction (XRD), SEM and transmission electron microscopy (TEM). Tribological experiments have been carried out to evaluate the friction and wear properties of the SFPB-treated sample in comparison with original sample. The effects of SFPB treatment on friction and wear behavior for AISI 52100 steel have been analyzed in details. Spherical Al2O3 powder with a diameter of 30μm is used as shot media in the SFPB treatment onto an AISI52100 steel. As the air pressure rises, the hardness of treated surface layer increases as well. But when the air pressure rises to a critical value, microcracks and pores will be found in the treated surface layer. Then the hardness of surface layer decreases dramatically. In terms of annealed AISI52100 steels, the optimized air pressure value is 1.5MPa; in terms of quenched AISI52100 steels, the optimized air pressure value is 2.0MPa. In terms of annealed AISI52100 steel, in the air pressure of 1.5MPa, as the time of SFPB-treatment increases, the thickness of deformed layer increases. But when the treating time passes over a critical value, some microcracks and pores will be fabricated in the surface layer of SFPB-treated sample. In terms of quenched AISI52100 steel, in the air pressure of 2.0MPa, as the time of SFPB-treatment increases, the thickness of deformed layer will increase as well. But when the treating time passes over a certain value, the thickness of deformed layer will not increase any more. So under the optimized air pressure of SFPB treatment, the optimized treating time for the annealed sample is 2s in one square centimetre, while the optimized treating time for the quenched sample is 0.4s in one square centimetre. When a quenched AISI52100 steel roll is treated by SFPB treatment, the heating temperature of compressed air will change the surface roughness of steel roll. As the heating temperature rises, the surface roughness increases as well. When the heating temperature of compressed air stays at the room temperature, the surface roughness will increase to 1.5μm. With this surface roughness, the quality of sheet steel will be the best. After SFPB treatment, a nanostructured surface layer is fabricated in the AISI52100 steel. For an annealed sample, the thickness of nanostructured layer is about 15μm, and the average grain size of top surface layer is about 20nm. For a quenched sample, the thickness of nanostructured layer is about 5μm, and the average gain size of top surface layer is about 30~60nm.After SFPB treatment, phase transition occurs in the surface layer of the treated samples. For the annealed sample, cementite in the subsurface layer of the annealed AISI52100 steel experiences plastic deformation and refinement; cementite in the outermost surface layer has dissolved completely. For the quenched AISI52100 steel, martensite phase transition and cementite dissolution occur at the same time in the surface layer. After SFPB treatment, spherical dimples have scattered randomly on the treated surface. For the annealed sample, the roughness is 1.9μm; For the quenched sample, the roughness is 1.2μm. A hardened surface layer has been fabricated in the AISI52100 steel. The thickness of the hardened surface layer is about 70μm. For the annealed sample, the maximum hardness value occurs at the outermost surface layer. For the quenched sample, the maximum hardness value occurs at the subsurface layer( about 10 μm deep from the surface) A quenched AISI52100 steel roll has been treated by SFPB. A residual compressive stress layer has been created in the treated roll. The maximum stress value comes to 745MPa in the outermost surface of the roll. Tribology experiment results show that under the normal load of 10N, SFPB-treated annealed sample possesses a higher friction coefficient and wear loss volume compared with the ones of an original sample. This phenomenon can be attributed to the higher surface roughness of the SFPB-treated sample. Under the normal loads between 20N and 40N, due to a higher hardness of the SFPB-treated sample, it has lower friction coefficient and wear loss volume compared with the original sample. For the SFPB-treated quenched AISI52100 steel, under the normal loads of 15N and 25N, due to the higher hardness of the SFPB-treated surface layer, SFPB-treated sample has a lower wear loss volume compared with the original sample. Under the normal loads of 50N and 75N, the wear process of the quenched AISI52100 steel is dominated by severe oxidational wear mechanism. Both the SFPB-treated sample and the original sample have experienced severe oxide film spalling during the tribology experiment. The improvement of wear resistance for the SFPB-treated sample is limited. "
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64434
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	劳远侠. 超音速微粒轰击AISI52100钢的表层组织与摩擦学性能研究[D]. 北京. 中国科学院金属研究所,2012.