铁基合金表面纳米化过程及相关金属学问题研究
|
摘要
随着纳米材料研究的不断深入与纳米技术的发展,将表面改性与纳米材料相结合来制备纳米晶块体材料受到了人们的重视,其特点是通过提高材料表面性能来提高构件服役性能。表面纳米化技术被认为是今后一段时间可将纳米材料应用于工程实际的最重要技术之一。目前,通过表面机械研磨技术(surface mechanical attrition treatment, SMAT),在许多金属材料表面己成功制备出一定厚度的纳米结构表层,即实现了表面纳米化。但是目前对于SMAT法实现金属材料表层纳米结构的形成过程、微观组织演变、性能与结构关系的研究仍然不够系统,还有许多基本问题需要进一步研究。因此深入系统地研究该方法中的纳米晶粒形成机制和应用具有十分重要的意义。
本论文对低碳钢SMAT过程进行了数值模拟,计算了低碳钢SMAT时表面层的应变、应变速率及应力,探讨了SMAT时应变速率对低碳钢形变机制和晶粒细化机理的影响。针对机械研磨表面时发现的反直观行为(永久变形可能在脉冲的反方向),通过模拟计算研究了实验条件下反直观现象的产生原因,讨论了板厚,撞击频率和研磨时间等对该现象的影响。
通过SMAT在纯铁和Q235低碳钢表面制备出了一层厚度约为40μm的全致密、无污染的纳米晶组织。运用金相显微镜(OM)、X射线衍射(XRD)、透射电子显微镜(TEM)等分析测试技术对SMAT后纯铁和低碳钢的微观组织结构进行了表征。
通过电化学实验、拉伸实验、硬度和摩擦磨损测试实验对纯铁和Q235低碳钢表面制备出的纳米晶材料的性能进行了讨论研究。对表面纳米化处理前后的纯铁和低碳钢在金属蒸气弧源离子注入机上进行了Ti离子注入,运用俄歇电子能谱仪分析了离子注入后Ti沿试样表面的深度分布,研究了表面纳米化预处理对纯铁和低碳钢离子注入的影响。
机械研磨纯铁时添加镍粉,在纯铁表面获得一层铁镍合金层,经过不同温度的热处理让合金过程进行得更完全,分析表征了合金层的组织结构和耐蚀性,初步探讨了铁和镍的扩散以及铁镍混合层的合金化过程。研究了采用不同粉体制备的表面合金层的摩擦磨损性能,探讨表面合金层的摩损机制。
得到的主要结论:
1、SMAT试样表面层的应变、应变速率和应力沿深度方向呈梯度变化,最表面20μm层的应变速率最大可达681 s-1。SMAT试样表面层的变形过程主要经过两个阶段:弹塑性变形阶段和动态回复阶段。塑性变形时的应变量和应变速率对于试样晶粒细化和处理后最终晶粒尺寸的大小起重要的作用。
2、数值分析证实了实验中得到的试板的永久变形在脉冲反方向的异常响应模式(反直观现象)的理论依据,它是材料非线性与几何非线性耦合的结果。反直观行为对各种参数极其敏感,载荷作用的方式对于动力反直观行为有较大影响。在本实验的高频冲击载荷作用下,作用时间的增加将使板获得的初始动能增加,此时只需要较小的外加载荷就能使试板达到一定的变形程度且获得足够的能量,同时可使得发生反直观行为的载荷值的范围扩大,因此在本文的高频冲击实验载荷条件下更容易出现反直观现象。
3、SMAT后试样表层形成约40μm厚的等轴、取向随机的纳米晶组织,纯铁的平均晶粒尺寸约为15nm,低碳钢的约为30nm。距离试样表面深度的增加材料变形呈梯度变化,微观组织依次可以分为:纳米晶层,亚微米晶层、过渡层和基体。
4、SMAT后试样表面层的显微硬度显著提高,并且随着深度的增大显微硬度值逐渐减小,表面纳米层的显微硬度约为心部基体硬度的两倍,表面硬度的增大可归因于晶粒细化和加工硬化的协同作用。
5、SMAT后纯铁的耐蚀性降低而Q235低碳钢的略有提高。纯铁耐腐蚀性降低主要是由于纯铁硬度小,SMAT使最表层的纳米晶较小(~15nm),表面形成的纳米晶结构中存在有大量的微裂纹,试样的表面不平整度很高,这些均导致了表面纳米化后纯铁抗腐蚀能力下降。由于低碳钢本身硬度较高,变形抗力较大,SMAT后纳米晶粒的尺寸相对较大(~30nm),且塑性变形相对要小,表面经历了一定厚度的轧制,且表面微裂纹少,粗糙度相对纯铁试样要低,因此耐腐蚀的能力提高。
6、SMAT使纯铁试样整体抗拉强度明显增大,弹性模量(斜率)减小,伸长率下降。而试样再次经过短时的低温退火处理后,弹性模量有所提高,原因可能是残余应力和缺陷的减少。抗拉强度提高的主要原因是SMAT使纯铁表面层晶粒的细化;晶粒细化的同时表面一定厚度经历了轧制,表面存在残余压应力,有效阻碍裂纹的形成;表层的纳米晶层对基体约束,能有效阻碍基体中滑移带的发展,阻止基体材料的硬化,从而有效提升了材料整体的抗拉强度。
7、Ti注入纯铁和Q235钢后,注入元素浓度在经过表面纳米化处理的试样中比未经处理的有了很大的提高,主要原因是SMAT所产生的空位、晶界及位错等缺陷与注入元素发生交互作用,导致了注入元素固溶度的超额增加; SMAT提高了试样表面层的扩散能力也使得SMAT后试样注入元素的浓度提高。离子注入的深度变化不大。
8、表面纳米化提高了纯铁和低碳钢在中等载荷作用下的耐磨性,明显地降低了摩擦系数。表面纳米化有助于减弱纯铁和低碳钢表面的疲劳磨损效应。
9、SMAT纯铁时在试样罐中添加镍粉,经过100min的处理,镍粉均匀镶嵌在纯铁基体上,并形成约100μm厚的铁镍合金层,界面微观研究表明表面机械研磨时存在显著的原子扩散,实现了金属表面合金化,适当的热处理增强合金化程度,是一种新的金属表面合金化方法。
10、纯铁表面纳米合金化有助于提高材料在中等载荷下的耐磨性,摩擦系数较表面纳米层的低。在相同载荷下,加入二氧化锆粉体的表面合金层最耐磨,加入碳化钨、碳粉及镍粉的合金表面的耐磨性顺序依次降低,但均高于纯铁纳米晶层的耐磨性。表面合金层和表面纳米晶具有高的强度和硬度,摩擦副压入表层的深度小,对试样表面运动的阻力较小,导致了表面合金化后纯铁试样的摩擦系数和磨粒磨损所造成的磨损量小。
With the development of research on the technique and properties of nanostructured(NC)materials, it is reasonable to achieve surface modification by the generation of a nanostructured surface layer so that the overall properties and behavior of the material are significantly improved. It is validated that surface nanocrystallization(SNC) is one of the most important techniques, which can apply the NC materials into practice engineering. A certain depth of nanostructured surface layer has been successfully obtained in many material systems. Nevertheless, up to now, clear scenery of the process, microstructures and properties of the nanostructure surface layer is still lacking. There are many basical problems need to solve. Therefore, it is important to study the underlying mechanism for grain refinement by plastic straining.
In this work, Strain, strain rate and stress of surface layer of Q235 low carbon steel sample during SMAT were investigated by finite element method, the effect of strain rate on deformation and grain refinement mechanism of Q235 low carbon steel during SMAT was proposed. The phenomenon of counterintuitive behavior which refers that permanent deflection is in the opposite direction of the load is found in the process of SMAT. In this paper, detailed numerical analysis on dynamic counterintuitive response of plates under current conditions i.e. subjected to continued short pulse loading have been studied. This dynamic behavior shows sensitivity to those factors such as plate depth, impact frequency and process time. The effects of these factors have been discussed.
Porosity-free and contamination-free nanostructure surface layers with thickness about 40μm were fabricated on pure iron and Q235 low carbon steel plate respectively by using SMAT. Microstructural characterization of the nanostructure surface layer was investigated by means of X-ray diffraction (XRD), transmission electron microscope (TEM) and optical microscope(OM).
Electrochemistry experiment, tensile test, hardness measurements, friction and wear test have been carried out to investigate the properties of the fabricated surface nano-crystalline layer. Ti ion was implanted into the SMA treated samples and untreated coarse-grained samples by using Metal Vapor Vacuum Arc (MEVVA) source implanters, concentration distribution of Ti along the depth of sample was measured by means of Auger electron spectroscopy (AES). The effect of SNC on ion implantation in pure iron and Q235 low carbon steel was investigated.
And a layer of Fe/Ni alloy surface layer was fabricated by appending Ni powder into the container during the process of pure iron specimen SMAT. To accelerate the inter-diffusion of Fe and Ni and the alloying process, the specimens have been annealed at different temperatures. The friction and wear behavior of alloy surface layers by appending different powders were studied, and the friction and wear mechanism were discussed.
The main results are given as follows:
1 Strain, strain rate and stress gradually decrease along the depth of sample during SMAT. During SMAT, the strain rate of the 20μm top surface layer can reach 681s-1. There involve two stages during SMAT: elastic-plastic deformation stage and dynamical recovery stage. Strain and strain rate play an important role in the grain refinement process and final stabilized grain size after SMAT.
2 Detailed numerical analysis have validated that the anomalous response of the plate after SMAT is counterintuitive behavior, which could be considered as the result of coupling of material nonlinearity and geometry nonlinearity. The counterintuitive behavior shows intense to many factors, especially to the manner of the loads. Under the conditions offered by SMAT, the increase of process time should enhance the original kinetic energy of the plate. So that only with smaller load, the plate can obtain a certain deformation and adequate energy. Accordingly, the loading range can be enlarged and the counterintuitive behavior can be achieved more easily under current conditions.
3 Equiaxed nanocrystallines with random crystallographic orientations were obtained in the 40μm surface layer of pure iron and Q235 low carbon steel by means of SMAT, the average grain size of the nanocrystallines ia approximates 30nm for Q235 and 15nm for pure iron. Based on the gradient variation of microstructure, the microstructure of the plastic deformed surface layer can be subdivided into four sections along depth from the top treated surface: nanostructure region,submicro-grained region, transition region and the base.
4 After SMAT, the micro-hardness of the surface layer in the copper samples is evidently enhanced. The hardness decreases gradually with the increase in depth, and the micro-hardness of the surface layer is twice more than that of the original sample. The increased micro-hardness on the surface layer of nanocrystalline may be attributed to the refinement of grains and work-hardening.
5 After SMAT, the corrosion property is downgrade for pure iron and that is upgrade for Q235 low carbon steel specimen. The main reason for the worsen corrosion resistance for the SMATed pure iron is that pure iron is with lower hardness and weaker competence of withstanding deformation, which cause finer grain size and much more micro-crack in the surface layer. Pure iron surface shows coarser than that of Q235 after SMAT. In the opposites, low carbon steel Q235 specimen is with higher hardness which induces the higher counter-distortion force during SMAT. The degree of deformation after SMAT is lower than pure iron. The grain size of nano-crystalline is larger than that of pure iron. The surface has been rolled and with little micro-cracks. Thus SMATed low carbon steel specimen exhibit better corrosion resistance.
6 Compared with the original material, the SMATed pure iron specimen’s elastic modulus decreases, yield strength and tensile strength increases while elongation decreases. After a short time of low temperature anneal treatment, the specimen’s elastic modulus increased once more. The reason may be the decrease of the residual stress and density of defects grain boundary disorientation during anneal treatment. The main reason for the improvement of yield strength and tensile strength is that the surface grains have been refine to nano-grade during SMAT. Accompany SMAT, surface layer has been rolled, there exist remainder compress stress in the surface layer, which can effectively counteract the form of crack. At the same time, the surface nano-grains’layer can effectively block off the development of the slippages in the base metal and prevent the rigidification of the base metal.
7 After Ti has been implanted into pure iron and Q235 low carbon steel, compared to untreated coarse-grained samples, implantation concentration of Ti in the samples after SMAT increases dramatically. The main reason maybe that the solid solubility of implanted element has been enhanced, which is caused by the interaction of the implanted elements and the defects produced during the SMAT process such as vacancies, grain boundaries and dislocations. And at the same time the ion diffusion coefficient has been enlarged after SMAT,which may contribute to the increase of implantation concentration. The implantation depth changes little.
8 The friction and wear properties of the pure iron and Q235 were improved and the friction coefficients clearly decreased by means of SMAT. The nanocrystalline layer may reduce the effect of fatigue wear.
9 Nickel powders were added to the sample container during SMAT for a pure iron plate. After 100min, Ni powders were welded into the surface of iron plates and a homogeneous layer of Fe/Ni alloy with 100μm depth is formed on the surface of Fe base. Studies on the interface microstructure indicated that there was significant atomic diffusion and formation of an alloying layer during SMAT process. And the degree of alloying is enhanced after proper heat treatment process. A new method of surface alloying of metals has been developed.
10 Surface nano-alloy reduces the degree of plastic removal and surface fatigue fracture under the moderate load respectively. The friction and wear properties of the pure iron have been improved by means of surface nano-alloy. With the same loading, the ZrO2 alloy layer shows the best wear resistance, the WC, C and Ni alloy layers’wear resistance show descend in turn, and higher than the SMATed pure iron. The improvement in friction and wear properties may be attributed to the harder surface alloy layer and NC surface layer which reduces the press depth, the moving resistance, the degree of plowing and micro-cutting during the friction and wear test.
本论文对低碳钢SMAT过程进行了数值模拟,计算了低碳钢SMAT时表面层的应变、应变速率及应力,探讨了SMAT时应变速率对低碳钢形变机制和晶粒细化机理的影响。针对机械研磨表面时发现的反直观行为(永久变形可能在脉冲的反方向),通过模拟计算研究了实验条件下反直观现象的产生原因,讨论了板厚,撞击频率和研磨时间等对该现象的影响。
通过SMAT在纯铁和Q235低碳钢表面制备出了一层厚度约为40μm的全致密、无污染的纳米晶组织。运用金相显微镜(OM)、X射线衍射(XRD)、透射电子显微镜(TEM)等分析测试技术对SMAT后纯铁和低碳钢的微观组织结构进行了表征。
通过电化学实验、拉伸实验、硬度和摩擦磨损测试实验对纯铁和Q235低碳钢表面制备出的纳米晶材料的性能进行了讨论研究。对表面纳米化处理前后的纯铁和低碳钢在金属蒸气弧源离子注入机上进行了Ti离子注入,运用俄歇电子能谱仪分析了离子注入后Ti沿试样表面的深度分布,研究了表面纳米化预处理对纯铁和低碳钢离子注入的影响。
机械研磨纯铁时添加镍粉,在纯铁表面获得一层铁镍合金层,经过不同温度的热处理让合金过程进行得更完全,分析表征了合金层的组织结构和耐蚀性,初步探讨了铁和镍的扩散以及铁镍混合层的合金化过程。研究了采用不同粉体制备的表面合金层的摩擦磨损性能,探讨表面合金层的摩损机制。
得到的主要结论:
1、SMAT试样表面层的应变、应变速率和应力沿深度方向呈梯度变化,最表面20μm层的应变速率最大可达681 s-1。SMAT试样表面层的变形过程主要经过两个阶段:弹塑性变形阶段和动态回复阶段。塑性变形时的应变量和应变速率对于试样晶粒细化和处理后最终晶粒尺寸的大小起重要的作用。
2、数值分析证实了实验中得到的试板的永久变形在脉冲反方向的异常响应模式(反直观现象)的理论依据,它是材料非线性与几何非线性耦合的结果。反直观行为对各种参数极其敏感,载荷作用的方式对于动力反直观行为有较大影响。在本实验的高频冲击载荷作用下,作用时间的增加将使板获得的初始动能增加,此时只需要较小的外加载荷就能使试板达到一定的变形程度且获得足够的能量,同时可使得发生反直观行为的载荷值的范围扩大,因此在本文的高频冲击实验载荷条件下更容易出现反直观现象。
3、SMAT后试样表层形成约40μm厚的等轴、取向随机的纳米晶组织,纯铁的平均晶粒尺寸约为15nm,低碳钢的约为30nm。距离试样表面深度的增加材料变形呈梯度变化,微观组织依次可以分为:纳米晶层,亚微米晶层、过渡层和基体。
4、SMAT后试样表面层的显微硬度显著提高,并且随着深度的增大显微硬度值逐渐减小,表面纳米层的显微硬度约为心部基体硬度的两倍,表面硬度的增大可归因于晶粒细化和加工硬化的协同作用。
5、SMAT后纯铁的耐蚀性降低而Q235低碳钢的略有提高。纯铁耐腐蚀性降低主要是由于纯铁硬度小,SMAT使最表层的纳米晶较小(~15nm),表面形成的纳米晶结构中存在有大量的微裂纹,试样的表面不平整度很高,这些均导致了表面纳米化后纯铁抗腐蚀能力下降。由于低碳钢本身硬度较高,变形抗力较大,SMAT后纳米晶粒的尺寸相对较大(~30nm),且塑性变形相对要小,表面经历了一定厚度的轧制,且表面微裂纹少,粗糙度相对纯铁试样要低,因此耐腐蚀的能力提高。
6、SMAT使纯铁试样整体抗拉强度明显增大,弹性模量(斜率)减小,伸长率下降。而试样再次经过短时的低温退火处理后,弹性模量有所提高,原因可能是残余应力和缺陷的减少。抗拉强度提高的主要原因是SMAT使纯铁表面层晶粒的细化;晶粒细化的同时表面一定厚度经历了轧制,表面存在残余压应力,有效阻碍裂纹的形成;表层的纳米晶层对基体约束,能有效阻碍基体中滑移带的发展,阻止基体材料的硬化,从而有效提升了材料整体的抗拉强度。
7、Ti注入纯铁和Q235钢后,注入元素浓度在经过表面纳米化处理的试样中比未经处理的有了很大的提高,主要原因是SMAT所产生的空位、晶界及位错等缺陷与注入元素发生交互作用,导致了注入元素固溶度的超额增加; SMAT提高了试样表面层的扩散能力也使得SMAT后试样注入元素的浓度提高。离子注入的深度变化不大。
8、表面纳米化提高了纯铁和低碳钢在中等载荷作用下的耐磨性,明显地降低了摩擦系数。表面纳米化有助于减弱纯铁和低碳钢表面的疲劳磨损效应。
9、SMAT纯铁时在试样罐中添加镍粉,经过100min的处理,镍粉均匀镶嵌在纯铁基体上,并形成约100μm厚的铁镍合金层,界面微观研究表明表面机械研磨时存在显著的原子扩散,实现了金属表面合金化,适当的热处理增强合金化程度,是一种新的金属表面合金化方法。
10、纯铁表面纳米合金化有助于提高材料在中等载荷下的耐磨性,摩擦系数较表面纳米层的低。在相同载荷下,加入二氧化锆粉体的表面合金层最耐磨,加入碳化钨、碳粉及镍粉的合金表面的耐磨性顺序依次降低,但均高于纯铁纳米晶层的耐磨性。表面合金层和表面纳米晶具有高的强度和硬度,摩擦副压入表层的深度小,对试样表面运动的阻力较小,导致了表面合金化后纯铁试样的摩擦系数和磨粒磨损所造成的磨损量小。
With the development of research on the technique and properties of nanostructured(NC)materials, it is reasonable to achieve surface modification by the generation of a nanostructured surface layer so that the overall properties and behavior of the material are significantly improved. It is validated that surface nanocrystallization(SNC) is one of the most important techniques, which can apply the NC materials into practice engineering. A certain depth of nanostructured surface layer has been successfully obtained in many material systems. Nevertheless, up to now, clear scenery of the process, microstructures and properties of the nanostructure surface layer is still lacking. There are many basical problems need to solve. Therefore, it is important to study the underlying mechanism for grain refinement by plastic straining.
In this work, Strain, strain rate and stress of surface layer of Q235 low carbon steel sample during SMAT were investigated by finite element method, the effect of strain rate on deformation and grain refinement mechanism of Q235 low carbon steel during SMAT was proposed. The phenomenon of counterintuitive behavior which refers that permanent deflection is in the opposite direction of the load is found in the process of SMAT. In this paper, detailed numerical analysis on dynamic counterintuitive response of plates under current conditions i.e. subjected to continued short pulse loading have been studied. This dynamic behavior shows sensitivity to those factors such as plate depth, impact frequency and process time. The effects of these factors have been discussed.
Porosity-free and contamination-free nanostructure surface layers with thickness about 40μm were fabricated on pure iron and Q235 low carbon steel plate respectively by using SMAT. Microstructural characterization of the nanostructure surface layer was investigated by means of X-ray diffraction (XRD), transmission electron microscope (TEM) and optical microscope(OM).
Electrochemistry experiment, tensile test, hardness measurements, friction and wear test have been carried out to investigate the properties of the fabricated surface nano-crystalline layer. Ti ion was implanted into the SMA treated samples and untreated coarse-grained samples by using Metal Vapor Vacuum Arc (MEVVA) source implanters, concentration distribution of Ti along the depth of sample was measured by means of Auger electron spectroscopy (AES). The effect of SNC on ion implantation in pure iron and Q235 low carbon steel was investigated.
And a layer of Fe/Ni alloy surface layer was fabricated by appending Ni powder into the container during the process of pure iron specimen SMAT. To accelerate the inter-diffusion of Fe and Ni and the alloying process, the specimens have been annealed at different temperatures. The friction and wear behavior of alloy surface layers by appending different powders were studied, and the friction and wear mechanism were discussed.
The main results are given as follows:
1 Strain, strain rate and stress gradually decrease along the depth of sample during SMAT. During SMAT, the strain rate of the 20μm top surface layer can reach 681s-1. There involve two stages during SMAT: elastic-plastic deformation stage and dynamical recovery stage. Strain and strain rate play an important role in the grain refinement process and final stabilized grain size after SMAT.
2 Detailed numerical analysis have validated that the anomalous response of the plate after SMAT is counterintuitive behavior, which could be considered as the result of coupling of material nonlinearity and geometry nonlinearity. The counterintuitive behavior shows intense to many factors, especially to the manner of the loads. Under the conditions offered by SMAT, the increase of process time should enhance the original kinetic energy of the plate. So that only with smaller load, the plate can obtain a certain deformation and adequate energy. Accordingly, the loading range can be enlarged and the counterintuitive behavior can be achieved more easily under current conditions.
3 Equiaxed nanocrystallines with random crystallographic orientations were obtained in the 40μm surface layer of pure iron and Q235 low carbon steel by means of SMAT, the average grain size of the nanocrystallines ia approximates 30nm for Q235 and 15nm for pure iron. Based on the gradient variation of microstructure, the microstructure of the plastic deformed surface layer can be subdivided into four sections along depth from the top treated surface: nanostructure region,submicro-grained region, transition region and the base.
4 After SMAT, the micro-hardness of the surface layer in the copper samples is evidently enhanced. The hardness decreases gradually with the increase in depth, and the micro-hardness of the surface layer is twice more than that of the original sample. The increased micro-hardness on the surface layer of nanocrystalline may be attributed to the refinement of grains and work-hardening.
5 After SMAT, the corrosion property is downgrade for pure iron and that is upgrade for Q235 low carbon steel specimen. The main reason for the worsen corrosion resistance for the SMATed pure iron is that pure iron is with lower hardness and weaker competence of withstanding deformation, which cause finer grain size and much more micro-crack in the surface layer. Pure iron surface shows coarser than that of Q235 after SMAT. In the opposites, low carbon steel Q235 specimen is with higher hardness which induces the higher counter-distortion force during SMAT. The degree of deformation after SMAT is lower than pure iron. The grain size of nano-crystalline is larger than that of pure iron. The surface has been rolled and with little micro-cracks. Thus SMATed low carbon steel specimen exhibit better corrosion resistance.
6 Compared with the original material, the SMATed pure iron specimen’s elastic modulus decreases, yield strength and tensile strength increases while elongation decreases. After a short time of low temperature anneal treatment, the specimen’s elastic modulus increased once more. The reason may be the decrease of the residual stress and density of defects grain boundary disorientation during anneal treatment. The main reason for the improvement of yield strength and tensile strength is that the surface grains have been refine to nano-grade during SMAT. Accompany SMAT, surface layer has been rolled, there exist remainder compress stress in the surface layer, which can effectively counteract the form of crack. At the same time, the surface nano-grains’layer can effectively block off the development of the slippages in the base metal and prevent the rigidification of the base metal.
7 After Ti has been implanted into pure iron and Q235 low carbon steel, compared to untreated coarse-grained samples, implantation concentration of Ti in the samples after SMAT increases dramatically. The main reason maybe that the solid solubility of implanted element has been enhanced, which is caused by the interaction of the implanted elements and the defects produced during the SMAT process such as vacancies, grain boundaries and dislocations. And at the same time the ion diffusion coefficient has been enlarged after SMAT,which may contribute to the increase of implantation concentration. The implantation depth changes little.
8 The friction and wear properties of the pure iron and Q235 were improved and the friction coefficients clearly decreased by means of SMAT. The nanocrystalline layer may reduce the effect of fatigue wear.
9 Nickel powders were added to the sample container during SMAT for a pure iron plate. After 100min, Ni powders were welded into the surface of iron plates and a homogeneous layer of Fe/Ni alloy with 100μm depth is formed on the surface of Fe base. Studies on the interface microstructure indicated that there was significant atomic diffusion and formation of an alloying layer during SMAT process. And the degree of alloying is enhanced after proper heat treatment process. A new method of surface alloying of metals has been developed.
10 Surface nano-alloy reduces the degree of plastic removal and surface fatigue fracture under the moderate load respectively. The friction and wear properties of the pure iron have been improved by means of surface nano-alloy. With the same loading, the ZrO2 alloy layer shows the best wear resistance, the WC, C and Ni alloy layers’wear resistance show descend in turn, and higher than the SMATed pure iron. The improvement in friction and wear properties may be attributed to the harder surface alloy layer and NC surface layer which reduces the press depth, the moving resistance, the degree of plowing and micro-cutting during the friction and wear test.
引文
[1] R. Li, M. G. S. Ferreira, A. Almeida, R. Vilar, K. G. Watkins, M. A. McMahon, W. M. Steen, Localized corrosion of laser surface melted 2024-T351 aluminium alloy[J]. Surface and Coatings Technology, 1996, 81: 290-296
[2] You Wang, Radovan Kovacevic, Jiajun Liu, Mechanism of surface modification of CeO2 in laser remelted alloy spray coatings Wear 1998, 221: 47-53.
[3] V. P. Rotshtein, Yu. F. Ivanov, A. B. Markov, D. I. Proskurovsky, K. V. Karlik, K. V. Oskomov, B. V. Uglov, A. K. Kuleshov, M. V. Novitskaya, S. N. Dub, Y. Pauleau, I. A. Shulepov[J], Surface and Coatings Technology, 2006, 200: 6378-6386.
[4] Jeon G Han, Jae S Lee, Byung H Cho, Kim W, Guoyi Tang. Wear and fretting wear beaviour of ion-implanted zircaloy[J], Surface and Coatings Technology, 1996,83:307-312.
[5] Zhiyong He, Jinxiang Zhao, Zhong Xu. Plasma surface alloying of spheroidal graphite iron[J], Surface and Coatings Technology, 2000,131:574-578.
[6] N. Tsuji, S. Tanaka, T. Takasugi, Evaluation of surface-modified Ti–6Al–4V alloy by combination of plasma-carburizing and deep-rolling[J], Materials Science and Engineering A, 2008, 488: 139-145.
[7] C C Koch, D B Calvin, G G Mckamey, et al. Preparation of“amorphous”by mechanical alloying[J]. Applied Physics Letter, 1983,43(11):1017-1019
[8] Y. Ivanisenko, W. Lojkowski, R. Z. Valiev, H. J. Fecht, The mechanism of formation of nanostructure and dissolution of cementite in a pearlitic steel during high pressure torsion[J]. Acta Mater. 2003, 51: 5555-5560.
[9] A. V. Korznikov, O. Dimitrov, G. F. Korznikova, J. P. Dallas, A. Quivy, R. Z. Valiev, Nanocrystalline structure and phase transformation of the intermetallic compound TiAl processed by severe plastic deformation [J], NanoStruct Mater. 1999, 11: 17-23.
[10] X. Sauvage, F. Wetscher, P. Pareige, Acta Mater. 2005, 53: 2127-2136.
[11] A.Torosyan, L.Takacs. Mechanochemical reaction at the interface between a metal plate and oxide powders[J], Journal of Materials Science, 2004,39:5491-5496
[12] Lu K,Lu J. Surface Nanocrystallization (SNC) of metallic materials- presentation of the concept behind a new approach[J], J. Materials Science and Technology, 1999, 15: 193-197
[13]刘刚,雍兴平,卢柯金属材料表面纳米化的研究现状[J],中国表面工程,2001,(3):1-5
[14]徐滨士纳米表面工程[M],北京:化学工业出版社,2004
[15]卑多慧,吕坚,顾剑封.表面纳米化热处理对低碳钢气体渗氮行为的研究[J],材料热处理学报,2002,22(3):19
[16] Wang Z B, Lu J, Lu K. Chromizing behaviors of a low carbon steel processed by means of surface mechanical attrition treatment[J], Acta Materialia, 2005,53:2081
[17]卫英慧,林万明,侯利锋,杜华云,许并社.一种纯铜基板材表面合金化的工艺方法[P],中国专利,zl200610048372.7
[18] X. L. Wu, N. R. Tao, Q. M. Wei, P. Jiang , J. Lu , K. Lu, Microstructural evolution and formation of nanocrystalline intermetallic compound during surface mechanical attrition treatment of cobalt[J], Acta Materialia 2007, 55: 5768.
[19] P. Jiang, Q. Wei, Y. S. Hong, J. Lu, X. L. Wu, In situ synthesis of nanocrystalline intermetallic layer during surface plastic deformation of zirconium[J], Surface and Coatings Technology, 2007, 202: 583.
[20]沈长斌,王胜刚,龙康等.块体纳米晶工业纯铁在室温硫酸溶液中的腐蚀电化学行为[J].机械工程材料,2005 ,29 (4): 48.
[21] Z. B. Wang , N. R. Tao , S. Li , W. Wang , G. Liu ,J. Lu ,K. Lu , Effect of surface nanocrystallization on friction and wear properties in low carbon steel[J], Materials Science and Engineering, 2003, A352: 144-149
[22] Y. S. Zhang, Z. Han, K. Lu,Fretting wear behavior of nanocrystalline surface layer of copper under dry condition[J],Wear, 2008, 265: 396–40
[23] H. Q. Sun , Y. N. Shi, M. X. Zhang,Wear behaviour of AZ91D magnesium alloy with a nanocrystalline surface layer[J] , Surface & Coatings Technology. 2008, 202: 2859–2864
[24] Liu J J. Principles of Wear of Materials and Its Wear Resistance. Beijing: Tshinghua Univercity Press, 1993: 158.
[2] You Wang, Radovan Kovacevic, Jiajun Liu, Mechanism of surface modification of CeO2 in laser remelted alloy spray coatings Wear 1998, 221: 47-53.
[3] V. P. Rotshtein, Yu. F. Ivanov, A. B. Markov, D. I. Proskurovsky, K. V. Karlik, K. V. Oskomov, B. V. Uglov, A. K. Kuleshov, M. V. Novitskaya, S. N. Dub, Y. Pauleau, I. A. Shulepov[J], Surface and Coatings Technology, 2006, 200: 6378-6386.
[4] Jeon G Han, Jae S Lee, Byung H Cho, Kim W, Guoyi Tang. Wear and fretting wear beaviour of ion-implanted zircaloy[J], Surface and Coatings Technology, 1996,83:307-312.
[5] Zhiyong He, Jinxiang Zhao, Zhong Xu. Plasma surface alloying of spheroidal graphite iron[J], Surface and Coatings Technology, 2000,131:574-578.
[6] N. Tsuji, S. Tanaka, T. Takasugi, Evaluation of surface-modified Ti–6Al–4V alloy by combination of plasma-carburizing and deep-rolling[J], Materials Science and Engineering A, 2008, 488: 139-145.
[7] C C Koch, D B Calvin, G G Mckamey, et al. Preparation of“amorphous”by mechanical alloying[J]. Applied Physics Letter, 1983,43(11):1017-1019
[8] Y. Ivanisenko, W. Lojkowski, R. Z. Valiev, H. J. Fecht, The mechanism of formation of nanostructure and dissolution of cementite in a pearlitic steel during high pressure torsion[J]. Acta Mater. 2003, 51: 5555-5560.
[9] A. V. Korznikov, O. Dimitrov, G. F. Korznikova, J. P. Dallas, A. Quivy, R. Z. Valiev, Nanocrystalline structure and phase transformation of the intermetallic compound TiAl processed by severe plastic deformation [J], NanoStruct Mater. 1999, 11: 17-23.
[10] X. Sauvage, F. Wetscher, P. Pareige, Acta Mater. 2005, 53: 2127-2136.
[11] A.Torosyan, L.Takacs. Mechanochemical reaction at the interface between a metal plate and oxide powders[J], Journal of Materials Science, 2004,39:5491-5496
[12] Lu K,Lu J. Surface Nanocrystallization (SNC) of metallic materials- presentation of the concept behind a new approach[J], J. Materials Science and Technology, 1999, 15: 193-197
[13]刘刚,雍兴平,卢柯金属材料表面纳米化的研究现状[J],中国表面工程,2001,(3):1-5
[14]徐滨士纳米表面工程[M],北京:化学工业出版社,2004
[15]卑多慧,吕坚,顾剑封.表面纳米化热处理对低碳钢气体渗氮行为的研究[J],材料热处理学报,2002,22(3):19
[16] Wang Z B, Lu J, Lu K. Chromizing behaviors of a low carbon steel processed by means of surface mechanical attrition treatment[J], Acta Materialia, 2005,53:2081
[17]卫英慧,林万明,侯利锋,杜华云,许并社.一种纯铜基板材表面合金化的工艺方法[P],中国专利,zl200610048372.7
[18] X. L. Wu, N. R. Tao, Q. M. Wei, P. Jiang , J. Lu , K. Lu, Microstructural evolution and formation of nanocrystalline intermetallic compound during surface mechanical attrition treatment of cobalt[J], Acta Materialia 2007, 55: 5768.
[19] P. Jiang, Q. Wei, Y. S. Hong, J. Lu, X. L. Wu, In situ synthesis of nanocrystalline intermetallic layer during surface plastic deformation of zirconium[J], Surface and Coatings Technology, 2007, 202: 583.
[20]沈长斌,王胜刚,龙康等.块体纳米晶工业纯铁在室温硫酸溶液中的腐蚀电化学行为[J].机械工程材料,2005 ,29 (4): 48.
[21] Z. B. Wang , N. R. Tao , S. Li , W. Wang , G. Liu ,J. Lu ,K. Lu , Effect of surface nanocrystallization on friction and wear properties in low carbon steel[J], Materials Science and Engineering, 2003, A352: 144-149
[22] Y. S. Zhang, Z. Han, K. Lu,Fretting wear behavior of nanocrystalline surface layer of copper under dry condition[J],Wear, 2008, 265: 396–40
[23] H. Q. Sun , Y. N. Shi, M. X. Zhang,Wear behaviour of AZ91D magnesium alloy with a nanocrystalline surface layer[J] , Surface & Coatings Technology. 2008, 202: 2859–2864
[24] Liu J J. Principles of Wear of Materials and Its Wear Resistance. Beijing: Tshinghua Univercity Press, 1993: 158.