表面机械研磨处理对X80管线钢焊接接头组织与性能的影响

采用表面机械研磨处理(SMAT)技术对X80管线钢焊接接头进行了30,60及90 min表面纳米化处理,分别采用光学显微镜、X射线衍射仪、表面粗糙度仪及显微硬度计等研究了SMAT不同时间后X80管线钢焊接接头的显微组织、晶粒尺寸、表面粗糙度及显微硬度的变化。结果表明:SMAT不同时间后均可在X80管线钢焊接接头表面获得一定厚度的塑性变形层,且随着SMAT时间的延长,塑性变形层厚度逐渐增加,实现了焊接接头的表面纳米化(组织均匀化);SMAT可以显著提高焊接接头表面的显微硬度,使显微硬度沿深度呈梯度分布;SMAT还可改善焊接接头表面粗糙度,随SMAT时间的延长表面粗糙度逐渐减小。     

GH4169 高能喷丸表面纳米化的研究

采用GH4169高温舍金进行高能喷丸表面纳米化试验,通过X射线衍射、透射电镜、扫描电镜、能谱及硬度测试等方法对不同时间喷丸后材料表面晶粒尺寸、形貌以及变形层硬度进行分析.结果表明:喷丸5 min实现表面纳米化,表面晶粒尺寸约为58.25 nm,随着喷丸时间的延长,晶粒逐渐细化,在喷丸30 min时,表层晶粒尺寸约为21.41 nm,强烈变形层深度达到8 μm,表面硬度约为HV480,继续延长时间,表层晶粒尺寸变化不大,在喷丸120 min时,表层晶粒尺寸约为20.27 nm,表面硬度约为HV600,强烈变形层深度达到40 μm.     

7050铝合金的表面增压喷丸纳米化

在普通喷丸设备上加增压罐,采用增压喷丸方法对7050铝合金表面进行喷丸处理;用X射线衍射仪、光学显微镜、透射电镜、选区电子衍射仪等对合金表层结构进行了观察与分析,并用显微硬度计测试了表层的硬度。结果表明:经增压喷丸处理后7050铝合金表层的衍射峰明显宽化,随着处理时间的增加,塑性变形层厚度增加,表层晶粒细化至纳米级,平均晶粒尺寸约为40 nm;纳米化后的合金表层硬度比心部硬度提高了1.5倍,其原因可归结为细晶强化及加工硬化。     

纯铁经表面机械研磨处理后微结构参量的表征

用X射线线形分析法(XLPA)测定了经表面机械研磨处理(SMAT)后纯铁的有效晶粒(亚晶)尺寸、微观应变、位错密度和体弹性储能密度,用TEM观察了组织形貌,并与40%拉伸试样进行了对比.结果表明:纯铁经SMAT 90 min后,平均位错密度高达1.0×10 16m-2,表面亚晶粒尺寸在7 nm左右;相对拉伸而言,SMAT对晶粒细化和引入微观应变的效果十分明显;XLPA法与TEM法得到的晶粒尺寸基本一致.     

16MnR焊接接头高能喷丸表面强化的研究

采用16MnR压力容器钢气体保护焊接头进行高能喷丸表面强化试验,利用金相显微镜、扫描电镜、硬度测试以及X射线衍射等方法对不同时间喷丸处理的表层组织形貌、变形层硬度以及晶粒尺寸进行了分析。结果表明,焊接接头的焊缝、热影响区和母材随着喷丸时间的延长,晶粒逐渐细化,表层硬度和硬化层深度逐渐增加,显微硬度随着距表层深度的增加而降低,当喷丸时间120min时,焊缝、热影响区、母材表层硬度可分别提高240HV、215HV、223HV。喷丸时间继续增加,硬度值增幅不明显。综合喷丸时间对表层组织、硬度和变形层深度的影响,焊接接头各区结果都显示120min喷丸处理的样品强化效果最佳。     

表面纳米化焊接接头组织和结构

采用超声速微粒轰击技术对0Cr18Ni9Ti不锈钢和16MnR合金钢焊接接头进行表面纳米化处理,利用金相显微镜、透射电镜和X射线衍射对材料表面的微观组织和表层结构进行分析与表征,并利用显微硬度仪对硬度沿厚度方向的变化进行分析。结果表明：经超声速微粒轰击处理后,0Cr18Ni9Ti不锈钢和16MnR合金钢两种焊接接头的晶粒尺寸由里及表逐渐减小,据表层70 µm处,晶粒尺寸平均分别为94.8、89.4 nm,样品表层晶粒尺寸平均分别为22、20 nm;0Cr18Ni9Ti不锈钢和16MnR合金钢焊接接头表层硬度分别提高至570 HV及470 HV左右,是内部硬度的2倍以上。母材、热影响区、焊缝三个区域的硬度在表层趋于一致,表层组织得到均一化。     

Cu-Cr合金触头电子束表面重熔初探与研究

Cu Cr合金触头材料中,Cr相的均匀细化能提高Cu-Cr合金触头的使用性能。利用高能电子束对Cu Cr40合金表面进行重熔处理;通过扫描电子显微镜对处理样品表面重熔层进行组织结构分析;采用X射线荧光仪对其主要成分进行定量检测。结果表明,Cu Cr40合金经电子束重熔扫描处理后,重熔层中Cu、Cr两相偏析程度减小,Cr相均匀、细化,Cr晶粒平均尺寸小于3μm;电子束工艺参数对重熔层表面形貌、组织和深度有较大影响;在适当的工艺参数下,重熔层中Cu、Cr分布均匀,成分比例未发生变化。     

超声加工对球墨铸铁表面粗糙度的影响及其机理

对球墨铸铁表面进行超声加工处理,通过白光共焦三维显微镜、扫描电子显微镜、光学显微镜和维氏硬度计等研究了加工区和未加工区的三维形貌、表面粗糙度、显微组织等。结果表明:超声加工对试样的尺寸影响很小,可实现连续抛光;加工区与未加工区的交界处有高约30μm的蝶形凸起;超声加工能显著降低试样的表面粗糙度,轮廓算术平均偏差由加工前的1.465μm减小到0.948μm,降低了35.29%;超声加工后,试样表层晶粒明显细化,表面硬度提高,超声加工对试样硬度的影响深度为0.6mm左右。     

表面纳米化处理对Cr5Mo钢流动加速腐蚀性能的影响

采用超声喷丸(USSP)技术对Cr5Mo钢表面进行纳米化处理,研究了试验钢表面的组织及显微硬度,并对超声喷丸前后试样在含H2S流动去离子水溶液中的流动加速腐蚀性能进行了研究,并对腐蚀产物膜的微观形貌进行了观察。结果表明:经USSP处理后,试样表面形成了一定深度的纳米晶层,该晶层内的平均晶粒尺寸约为20nm;表面纳米化能够明显提高试样表层的显微硬度,并且处理时间越长,显微硬度越大,变形层厚度越大;与原始粗晶试样相比,表面纳米化试样的抗流动加速腐蚀性能增强,表面生成的腐蚀产物膜较致密;随着USSP处理时间的延长,腐蚀产物膜的致密度和完整性变差,耐蚀性能逐渐下降。     

显微组织对Ti-15-3合金喷丸处理效果的影响

对Ti-15-3合金分别进行淬火、炉冷和淬火+500,540℃时效处理,得到不同的显微组织,然后进行相同工艺的喷丸处理,研究喷丸处理后合金显微组织、残余应力、硬度、表面粗糙度等的演化规律。结果表明:经喷丸处理后,淬火态合金组织中出现大量孪晶,炉冷态合金发生应力诱发马氏体相变,而时效态合金的显微组织无明显变化;喷丸处理后,淬火态合金的表层残余压应力最小,炉冷态的最大;淬火态合金的硬度最低,导致由喷丸处理所产生的塑性变形范围最大,表面粗糙度最大;炉冷态合金经喷丸处理后的表面硬度最大,塑性变形范围较小;500℃时效处理合金的硬度最高,喷丸处理后其表面粗糙度最小,时效温度升至540℃时,合金的硬度和塑性变形范围均减小。     

Electrochemical corrosion property of nanostructure layer of Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy

Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy was nanocrystallized with supersonic fine particles bombarding (SFPB). The microstructure features of nanocrystalline layer were determined by XRD, TEM, and microhardness tester. The electrochemical corrosion properties of the surface of original sample and the nanocrystallized sample surface were tested by CHI660 tester. That random crystallographic oriented particles (average grain size of 16 nm) were observed in the top surface layer of Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy, which could be attributed to the surface nanocrystallization. The electrochemical corrosion results show that the impedance of the sample nanolayer is reduced after SFPB with 30 min, and the corrosion resistance is lower than the original sample. The residual internal stress from the process of SFPB is one of the main factors to decrease the nanolayer corrosion resistance of Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy. However, the corrosion resistance is significantly recovered after stress relief annealing with 250–350 °C.     

纯铝表面机械研磨纳米化后的显微组织和硬度

对纯铝进行表面机械研磨处理形成纳米层,用XRD、TEM对表面纳米层进行了表征,并对沿深度方向的硬度变化进行分析.结果表明:晶粒细化后的主要微观特征是在原始晶粒内形成位错缠结、位错胞和高密度位错墙;随着应变的增加,这些位错组态逐渐演变成位错胞、亚晶、位错墙-显微带结构和层状胞块结构;随着应变和应变速率的进一步增加,晶粒细化遵循逐渐细分原则,逐渐在表面形成随机取向的纳米晶;与试样心部硬度相比,其表面硬度明显提高.     

Fretting wear behavior of nanocrystalline surface layer of copper under dry condition

Unlubricated fretting tests were performed with a nanocrystalline surface layer of a 99.99 wt.% copper fabricated by means of surface mechanical attrition treatment (SMAT), in comparison with a coarse-grained (CG) copper. The measured friction and wear data show that the fretting wear resistance is markedly enhanced with the nanocrystalline surface layer relative to the CG counterpart. The friction coefficient and wear volume of the SMAT Cu are lower than that of the CG Cu. For both samples, the friction coefficients and wear volumes increase with an increasing applied load and fretting frequency. A rapid increase of the friction coefficient and wear volume under an applied load above a critical value (30 N for the SMAT Cu and 20 N for the CG Cu) is noticed, corresponding to the formation of a continuous oxide layer between two contact surfaces. Also two sharp increases of the friction coefficient and wear volume at fretting frequencies of 50 Hz and 175 Hz were observed for the SMAT and the CG Cu. The former is correlated with the formation of a continuous oxide layer, while the latter corresponds to wearing away of the oxide layer.     

Microstructural characterization of Ti‐6Al‐4V alloy subjected to the duplex SMAT/plasma nitriding

In this study, microstructural characterization of Ti‐6Al‐4V alloy, subjected to the duplex surface mechanical attrition treatment (SMAT)/nitriding treatment, leading to improve its mechanical properties, was carried out through novel and original samples preparation methods. Instead of acid etching which is limited for morphological characterization by scanning electron microscopy (SEM), an original ion polishing method was developed. Moreover, for structural characterization by transmission electron microscopy (TEM), an ion milling method based with the use of two ions guns was also carried out for cross‐section preparation. To demonstrate the efficiency of the two developed methods, morphological investigations were done by traditional SEM and field emission gun SEM. This was followed by structural investigations through selected area electron diffraction (SAED) coupled with TEM and X‐ray diffraction techniques. The results demonstrated that ionic polishing allowed to reveal a variation of the microstructure according to the surface treatment that could not be observed by acid etching preparation. TEM associated to SAED and X‐ray diffraction provided information regarding the nanostructure compositional changes induced by the duplex SMAT/nitriding process. Microsc. Res. Tech. 76:897–903, 2013. © 2013 Wiley Periodicals, Inc.     

Tribological Behaviour of Pure Ti with a Nanocrystalline Surface Layer Under Different Loads

Surface mechanical attrition treatment (SMAT), a novel surface severe plastic deformation method, was carried out for titanium (Ti) to create a gradient-structured Ti (SMAT Ti). The tribological behaviour was studied under different loads and dry sliding conditions. The results showed that the deformation layer of SMAT Ti was about 160 μm. The friction and wear results showed that the wear resistance of SMAT Ti was enhanced compared to the coarse-grained (CG) counterpart. SMAT Ti showed abrasive wear under 1 and 5 N, and exhibited abrasive and adhesive wear under 2 N. While CG Ti showed abrasive and adhesive wear under 1–2 N, and exhibited abrasive wear under 5 N for the work hardening effects.     

Fretting wear behavior of nanocrystalline surface layer of pure copper under oil lubrication

Lubricated fretting tests in mineral oil were performed with a nanocrystalline surface layer on a pure bulk Cu prepared by surface mechanical attrition treatment (SMAT) against a WC-Co ball. It was found that the nanocrystalline surface layer exhibited a markedly enhanced fretting wear resistance and higher friction coefficient relative to the coarse-grained (CG) form. The wear volume of the SMAT Cu is one order of magnitude lower than that of the CG Cu. The friction coefficient of the SMAT Cu increases with an increasing load and frequency, while for the CG Cu, the friction coefficient increases with an increasing fretting frequency up to 100 Hz and thereafter decreases. The higher hardness of the SMAT Cu is suggested to be the main factor causing its improved wear resistance and higher friction coefficient. A discontinuous metal transfer layer can be found on the WC-Co ball only after fretting against the SMAT Cu, which may partly account for the higher wear resistance of the SMAT Cu in comparison with the CG Cu.     

导热能力对TC4合金高速干摩擦及其热行为的影响

采用具有较好导热性能的紫铜与TC4合金机械镶嵌，组成的销试样与纯TCA合金销试样的摩擦磨损特性及热行为特性进行对比研究。研究结果表明：随着摩擦功的增加，使用紫铜强化导热的TCA-紫铜组合销试样与纯TCA合金销试样的摩擦表面温度整体均为上升趋势，但是TC4-紫铜组合销试样的摩擦表面温度与纯TC4合金销试样相比有大幅度的降低，纯TC4合金销试样的表面温度在升高到一定程度以后由于相变吸收热量，其表面温度出现降低的趋势。使用紫铜强化导热后，摩擦副的摩擦因数有所提高，材料的耐磨性也有一定程度的提高。     

SLM成形表面织构对TC4钛合金干摩擦磨损性能的影响

基于一步法思路,采用金属3D打印机基于激光选区熔化（SLM）技术制备表面带有凹坑织构的TC4钛合金试样,采用光学相机、超景深显微镜和扫描电镜观察织构成形情况,利用激光共聚焦位移测试仪和显微维氏硬度计分别测试表面粗糙度和表面硬度,在干摩擦条件下采用摩擦磨损试验仪考察不同载荷下织构密度对TC4钛合金试样摩擦学性能的影响,并使用扫描电镜对摩擦实验前后的表面形貌进行分析。研究结果表明：一步法SLM成形能够在TC4钛合金表面获得成形良好的直径500 μm的织构;随着织构密度的提高,钛合金试样表面粗糙度增大,表面硬度有所降低;干摩擦条件下,提高TC4钛合金试样织构密度有利于磨屑的收集从而减少试样的三体磨损,提高载荷有利于改善摩擦副接触状态;5 N载荷下40%织构密度试样的平均摩擦因数和磨痕宽度均最小,与无织构试样相比,平均摩擦因数和磨痕宽度分别降低12%和16%;40%织构密度下,载荷提高会引起摩擦因数的降低和磨损量增大,磨损表面犁沟和片状剥落增多。在干摩擦条件下,3D打印一步法制备的表面织构可以显著改善TC4钛合金的磨粒磨损和黏着磨损。     

Influence of counterbody material on fretting wear behaviour of surface mechanical attrition treated Ti–6Al–4V

Surface mechanical attrition treatment (SMAT) was carried out on Ti–6Al–4V. Fretting wear tests were conducted using two counterbody materials (alumina and steel). SMAT resulted in surface nanocrystallization. Due to high hardness, low tangential force coefficient (TFC) and more TiO₂ layer, fretting wear resistance of SMAT treated samples was higher than that of the untreated samples. TFC values obtained with alumina counterbody were higher than those obtained with steel counterbody. The fretting wear resistance of untreated and treated samples fretted against alumina was lower than that of the samples fretted against steel due to tribochemical reactions at the contact zone.