Strain-induced Microstructure Refinement in a Tool Steel Subjected to Surface Mechanical Attrition Treatment

A nanostructured surface layer has been fabricated on an AISI H13 tool steel by means of surface mechanical attrition treatment (SMAT). Strain-induced refinement processes of ferrite grains and carbide particles have been investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) in the SMAT surface layer. Grain refinement of ferrite is found to be dominated by dislocation activities and greatly facilitated by a large number of carbide particles at a depth >20μm. The comparisons with microstructure refinement processes in other SMAT ferrite steels indicate that a larger volume fraction of carbide particles with a lower shear strength is expected to facilitate the refinement process of ferrite grains.     

Boriding kinetics of H13 steel

It is known that boriding has been employed to increase the service life of parts such as orifices; ingot molds, and dies for hot forming made of AISI H13 steel. In this study, case properties and kinetics of borided AISI H13 steel have been investigated by conducting a series of experiments in Ekabor-I powders at the process temperature of 1073, 1173 and 1273 K for periods of 1-5 h. The presence of borides FeB and Fe₂B of steel substrate was confirmed by optical microscopy and scanning electron microscopy (SEM). The results of this study indicated that the morphology of the boride layer has a smooth and compact morphology, and its hardness was found to be in the range of 1650-2000 HV. Transition zone observed between the hard boride coating and the matrix was relatively softer than the substrate. The kinetics of boriding shows a parabolic relationship between layer thickness and process time, and the calculated activation energy for the process is 186.2 kJ/mol. Moreover, boriding parameter BOP, which is only a function of boride layer thickness and activation energy, has been suggested for the prediction of layer thickness in boriding of AISI H13. There is a reasonable correlation between the progress of boride layer thickness and proposed time-temperature-compensated parameter. Similar findings have been found when it is applied to another steels including tool and low alloy steels, as well as Armco iron.     

Improved Fatigue Behavior of Pipeline Steel Welded Joint by Surface Mechanical Attrition Treatment (SMAT)

A pipeline steel X80 with welded joint was subjected to surface mechanical attrition treatment(SMAT).After SMAT,a nanostructure surface layer with an average grain size of about 10 nm was formed in the treated sample,and the fatigue limit of the welded joint was elevated by about 13% relative to the untreated joints.In the low and the high amplitude stress regimes,both fatigue strength and fatigue life were enhanced.Formation of the nanostructured surface layer played more important role in the enhanced fat...     

Pack boronizing of AISI H11 tool steel: Role of surface mechanical attrition treatment

The role of surface mechanical attrition treatment (SMAT) on pack boronizing of AISI H11 type tool steel is addressed. SMAT induced plastic deformation, enabled nanocrystallization at the surface, reduced the grain size and increased the volume fraction of non-equilibrium gain boundaries, increased the accumulation of defects and dislocations at the grain boundaries and within the grains. These features helped to promote the diffusion of boron during boronizing and increased the case depth and hardness of the borided layer. Duplex treatment on SMATed H11 steel samples helps to achieve a higher case depth when compared to the single stage treatment. The findings of the study suggest that SMAT can be used as a pre-treatment for boronizing of H11 tool steel.     

SMAT技术在油气输送管线焊后处理中的应用展望

概述了表面机械研磨技术(SMAT)的原理和研究现状,分析了SMAT技术特点,结合油气输送管线的生产及服役要求,分别就SMAT技术在改善油气输送管线焊接接头表面微观组织结构、提高油气输送管线焊接接头高低周疲劳性能、改善油气输送管线焊接接头残余应力分布和提高管线钢基体与防腐层结合能力等方面的应用进行了展望,认为SMAT技术在油气输送管线焊后处理中的应用具有广阔的前景.     

Annealing-induced Grain Refinement in a Nanostructured Ferritic Steel

A nanostructured surface layer with a mean ferrite grain size of ～8 nm was produced on a Fe-9Cr steel by means of surface mechanical attrition treatment. Upon annealing, ferrite grains coarsen with increasing temperature and their sizes increase to ～40 nm at 973 K. Further increasing annealing temperature leads to an obvious reduction of ferrite grain sizes, to ～14 nm at 1173 K. The annealing-induced grain refinement is analyzed in terms of phase transformations in the nanostructured steel.     

H13模具钢的应用及发展

介绍了H13钢的化学成分及特性。详尽论述了H13钢应用于热锻模、热挤压模和有色金属压铸模的现况。阐述了H13钢常规的淬火回火热处理工艺制度。从表面低温化学热处理、高能束表面处理和复合处理三个方面及微舍金化方面叙述了H13钢的最新研究动态。     

H13热作模具钢激光表面改性处理技术

介绍了H13热作模具钢的激光表面改性处理技术,分析了激光相变硬化、激光表面熔凝、激光合金化、激光冲击硬化等表面处理的特点及应用,研究了表面激光处理工艺的影响因素,以及激光在模具表面处理中的应用.讨论了表面激光改性处理存在的问题,提出了该领域的研究方向.     

基体表面粗糙度对H13钢板表面镀铬层的影响

分析测试H13钢表面镀铬层的表面形貌与结构、粗糙度、显微硬度、厚度、电化学阻抗及极化曲线,研究了H13钢基体表面粗糙度R_a对其表面镀铬层结构与性能的影响。结果表明:电镀时间小于30min时,随着R_a的增加,镀铬层晶粒尺寸减小,堆积趋于稀疏;电镀30 min后,不同R_a的镀铬层晶粒尺寸及分布基本相同;电镀60 min后,随着R_a的增加,镀铬层晶粒的尺寸明显增大;当R_a值小于0.504μm时,(200)面为铬晶粒的优势生长面,当R_a值为0.504μm时,(211)面为铬晶粒的优势生长面;随电镀时间的增加,镀铬层的厚度和显微硬度逐渐增大;当电镀时间相同时,随着R_a的减少,镀铬层的厚度减少,显微硬度增加,镀铬层的耐蚀性逐渐提高。     

Tensile properties of Cu with deformation twins induced by SMAT

High density nano-scale deformation twins were introduced in the surface layer of Cu sample by means of surface mechanical attrition treatment （SMAT） at room temperature. The Cu sample with deformation twins shows a yield strength of about 470 MPa in tension tests. The significant strengthening may be attributed to the effective inhibition of slip dislocations by abundant twin boundaries.     

Characterization and Properties of Nanostructured Surface Layer in a Low Carbon Steel Subjected to Surface Mechnaical Attrition

A nanostructured surface layer was synthesized on a low carbon steel by using surface mechanical attrition (SMA) technique,The refined microstructure of the surface layer was characterized by means of different techniques, and the hardness variation along the depth was examined,Experimental results show that the microstructure is inhomogeneous along the depth ,In the region from top surface to about 40 μm depth,the grain size increases from about 100 nm to 1000 nm ,The grain refinement can be associated with the activity of dislocations After the SMA treatment, the hardness of the surface layer is enhanced significantly compared with that of the original sample ,which cam primarily be attributed to the grain refinement.     

H13钢电弧沉积铝膜及强流脉冲电子束后处理的复合改性研究

本文介绍电弧沉积与强流脉冲电子束后处理相结合的表面复合处理工艺 ,并应用在H13钢的表面快速合金化。我们首先采用电弧离子镀的方法在H13钢表面沉积了约 10 μm厚的纯铝层 ,然后用强流脉冲电子束对铝膜进行后处理 ,Al在电子束瞬间加热作用下 ,熔入基体表面中 ,实现了表面快速合金化。对处理前后的样品进行了氧化性能对比测试 ,结果表明 ,复合处理可以显著提高H13钢在高温下的抗氧化性能     

Cr含量降低对H13钢组织与力学性能的影响

对比了Cr含量降低为3%的3Cr-H13钢与Cr含量为5%的传统H13钢性能的差异,利用SEM、TEM、XRD进行微观组织与相组成分析,研究了Cr对H13钢组织性能的影响。结果表明,Cr含量的降低明显提高了H13钢的回火稳定性与高温强度,其原因主要与回火组织中马氏体的回复程度及二次析出碳化物的种类有关。传统H13钢在650℃回火时,马氏体基本回复完全,基体强度明显下降,并在原马氏体板条界和晶界上析出了较多的尺寸为120nm左右的近球形Cr7C3和M6C型碳化物,第二相强化效果降低;而Cr含量降低为3%的3Cr-H13钢在650℃回火后,基体依然为板条马氏体,板条内保持较高的位错密度,同时板条内析出的大量细小弥散的短棒状VC,在起到弥散强化作用的同时还钉扎位错,推迟了马氏体的回复,从而提高了高温性能。     

H13钢冲头模具断裂原因分析

通过宏观检验、断口分析、EDS线扫描分析、化学成分分析、金相检验及硬度测试等方法,对H13钢冲头模具的断裂原因进行了分析。结果表明:冲头在法兰定位芯根部的倒角圆弧半径小,应力集中系数较大,且冲头材料化学成分偏析严重、组织不均匀,导致裂纹在法兰根部萌生后得以迅速扩展,造成了冲头的早期脆断。最后根据失效原因提出了相对应的改进措施和建议。     

不同温度和时间对SMAT黄铜基底生长ZnO纳米结构与形貌的影响

利用热氧化法,在不同氧化温度、保温时间条件下,在经过SMAT处理的Cu-Zn合金基底上生长出ZnO纳米线。采用X射线衍射、扫描电子显微镜、高分辨透射电子显微镜对样品结构、形貌进行了分析表征。结果表明:表面生长的纳米线为六方结构ZnO;氧化温度、保温时间对ZnO纳米线形貌有较大影响。总结了纳米线的生长机理。     

Characterization and Properties of Nanostructured Surface Layer in a Low Carbon Steel Subjected to Surface Mechanical Attrition

A nanostructured surface layer was synthesized on a low carbon steel by using surface mechanical attrition (SMA)technique. The refined microstructure of the surface layer was characterized by means of different techniques,and the hardness variation along the depth was examined. Experimental results show that the microstructure is in homogeneous along the depth. In the region from top surface to about 40 /zm deep, the grain size increases fromabout 10 nm to 100 nm. In the adjacent region of about 40~80 /zm depth, the grain size increases from about 100nm to 1000 nm. The grain refinement can be associated with the activity of dislocations. After the SMA treatment,the hardness of the surface layer is enhanced significantly compared with that of the original sample, which canprimarily be attributed to the grain refinement.     

钼离子注入束流大小对H13钢表层结构与耐磨性能的影响

利用金属蒸汽真空弧离子源引出的强束流钼离子，对H13钢进行了高剂量的离子注入。测量了注入试样的磨损性能，发现在注入剂量为3×1017cm－2、注入束流密度低于47μA·cm－2时，其耐磨性得到不同程度的改善。分别利用卢瑟福背散射谱（RBS）、X射线衍射（XRD）和X光电子能谱（XPS）测试了注入试样的表面成分及其微观结构。讨论了H13钢耐磨性的影响因素。     

表面机械研磨对H13钢表面性能的影响

使用表面机械研磨（SMA）方法处理H13钢表面使其表面获得一层变形层。采用SEM,TEM及硬度试验等检测方法对变形层的厚度、晶粒大小、截面硬度梯度和热稳定性等进行了分析;同时对H13钢在SMA处理前后的渗氮行为进行了比较。结果表明,经SMA处理后,H13钢表面形成了约10μm厚的变形层,变形层内的晶粒明显细化,并且这些晶粒具有较好的热稳定性;此外,可以大大提高H13钢渗氮的效率。     

纳米结构304不锈钢在硫酸溶液中的腐蚀行为

采用高频表面机械研磨方法在304不锈钢中制备出纳米晶和纳米孪晶结构。采用腐蚀失重试验和极化曲线测试等方法测试两种纳米结构304不锈钢在室温及80℃条件下5%硫酸溶液中的耐腐蚀性能,并利用透射电镜和扫描电镜分析其腐蚀性能和微观结构的关系。失重试验结果表明在80℃条件下5%硫酸溶液中,纳米孪晶比纳米晶结构的304不锈钢耐腐蚀性能好,以均匀腐蚀为主,点蚀为辅;而纳米晶则发生严重的点蚀。电化学测试结果表明:在室温条件下,纳米孪晶结构304不锈钢呈现高的自腐蚀电位和宽的钝化区间,但在80℃条件下,纳米晶和纳米孪晶结构304不锈钢的耐腐蚀性比粗晶不锈钢差。     

RE^＋＋N^＋注入对H13钢表面性能的影响

将混合稀土RE和氮离子注入到H13铜试样中。研究发现：这种方法能提高H13钢表面的纳米硬度;还能在高温下,延迟H13钢表面的氧化程度。因此,注RE^-＋N^＋能提高模具的寿命。