材料科学与工程 外文翻译 外文文献 英文文献 硼化物涂层的滑动和磨粒磨损行为

1、外文翻译硼化物涂层的滑动和磨粒磨损行为（c. martini, g. palombarini, g. poli, d. prandstraller）institute of metallurgy, university of bologna, viale risorgimento 4, bologna 40136, italy摘要由fe2b单内层和外层的feb所构成的多相硼化物涂层对铁和经渗碳处理的中碳钢有着深远的影响。根据滑动和磨损试验条件对样本的硼摩擦学行为进行了研究。发现不同地区的涂料的磨损率有很大的不同。铁硼化物晶体秩序解释了这些差异的原因。薄，易碎的涂料层构成的无序晶体对两种类型的抗

2、磨损行为影响不大。然后，构成fe2b单紧凑，高度有序的晶体的地区阻力增加到最高值。耐干滑动样本的硼优于通过提交替代表面处理样本资料（如气体氮化）和含量较低的awc钴硬质合金涂层。关键词：硼；铁；钢；滑动摩擦；磨粒摩擦；择优取向；晶体秩序；1 导言日益增加的需求与令人满意的电阻材料磨损与腐蚀性能促进了迅速扩张表面改性领域技术的发展。事实上，在许多应用中，这服务生活的组成部分是由表面特性所决定的。在这重要的热化学处理的钢种扩散的领域，如碳、氮和硼，硼处于一种特殊地位。一方面，即使在超过20个全球行动纲领，以及高耐磨性，经热化学处理的硼化物涂层涂料使普通钢材有了很高的硬度。硼钢构件在机械工程和汽车几

3、个摩擦学性能优良的工业中有很广泛的应用。值得注意的是，最好的结果是由粘固获得，即工序使用含有粉末的混合物进行硼化组件（如碳化硼），活化剂（通常kbf4），并最终加入稀释剂以控制潜在的硼化方法。然而，相对于气相渗硼，粉末渗硼在工业生产过程中：（一）比较复杂，费时和昂贵，（二）不适合过程控制和自动化，这种状况妨碍了充分传播渗硼处理工艺。努力加快工业气体渗过程的进展，就双方的加工条件和组成，硼化物层的孔隙度控制的主要问题加以解决，特别是，对等离子体及有关金属表面的相互作用机制缺乏了解。比如，硼化物涂层制作了两个中碳钢等离子辅助化学气相沉积法在833k采用bcl3与h2混合气体与ar稀释，只有几微米厚

4、，这两种渗硼层都很不好。另一方面，在汽车发动机的油泵驱动齿轮磨损性能的试验中，一个类似混合气体等离子体渗硼被发现与包渗硼相若。然而，获得单相层需要渗硼热处理，即涂层由含量较少但脆性不大的硼化物fe2b单铁组成。试图代替硼卤化物和允许种植单一fe2b单相层高达10微米厚的一中碳钢，任何进一步的发展有机前体乙硼烷硼体的方法正由渗碳的不利因素所影响。仅由未经处理的样品对这些硼化物层的摩擦学性能进行了评价。 在摩擦学行为上已经做了很多工作，特别是在非常不同的测试条件研究不同组成硼钢的耐磨性。主要问题集中在两个硼化物涂层独特的特点：（一）硬度高，这将提供一个高耐磨性；（二）柱状形态，这是一个涂层与基体之

5、间良好的附着力要求。很少致力于澄清损害的磨损机制，特别是涂层内铁的硼化物晶体取向的作用。众所周知，事实上，这热渗可引起铁硼化物fe2b单（四方）和硼（正交），一般都展示了强大的（0 0 2）择优取向。基合金成分对质地强度有显著的影响，作为一种合金元素的扩散，从基底涂层和改变涂层与基体的性质来改变材料性能。另一方面，有人指出，最外层几微米的硼化物涂层厚度地区晶体学紊乱，因此，应该通过硼化物的表面处理来消除它。本工作的目的是调查对钢铁生产的粘固硼化物涂层的耐磨性和滑动，特别是关于铁的硼化物晶体取向的影响，磨料磨损率的条件，测试。图1 滑块的示意图上缸摩擦计2实验细节2.1 材料和加工工艺阿姆科铁皮

6、（99.9纯）和中碳钢（38 nicrmo 4）统一在1000摄氏度真空退火，用600粒度碳化硅砂布纸表面抛光，然后在850c渗硼15小时并使用粉末混合组成的碳化硼（20），kbf4（10）和碳化硅（平衡）。用纯铁以便分析合金的基体和元素硼化物涂层之间的元素扩散。该硼化培养基组成，适用于多相涂料增长，由一个fe2b单内层和外层的硼组成。样本的硼特点被改变依靠光（奥姆手段）和扫描电子显微镜（sem）中，x射线衍射分析（xrd）和显微硬度测量（mhv）。x射线衍射分析利用计算机进行控制的测角仪和co、kr射线。铁的硼化物晶体学织构从外表面不同深度逐渐变薄与层涂层的层清除技术进行了评估。通过对交叉涂

7、层厚度截面金相与通常的技术准备，使用传统的维氏压头和0.5载荷，对材料的显微硬度进行了测量。滑动条件下的比较试验，中碳钢，也是在570摄氏度氮化气体（总深度处理鈭毫米）或10微米的硬铬涂层（硬度67-68hrc）的厚层。一个m 35工具钢（成分c 0.8，铬3.75，钼5.0之间，6.10，第五2.05，钴5.0），其硬金属层涂布（硬质合金有限公司18，硬度88hra）存放于空气等离子喷涂（aps）的技术，被选作参考，高耐磨材料。2.2 摩擦学测试干滑动进行了测试，采用计算机控制滑块上缸摩擦计（图1）。固定滑杆由研究中的材料在（5毫米× 5毫米× 50毫米）棱柱形式构成。该

8、构件材料是氧化铝陶瓷涂层的组成（重量比87）和二氧化钛（洛氏硬度= 60，表面粗糙度ra = 0.5微米），沉积在旋转圆筒。这些测试下进行了5和25n和外加负载，滑动速度0.18ms - 1，滑动距离达5公里，在室温下（20-25c）和在实验室的空气，（在相对湿度范围50 -60）。双方摩擦磨损性和制度（即两个滑块和气缸磨损累计）的连续测量了一弯曲载荷单元的手段和位移传感器，分别被作为滑动距离函数记录。在每个测试结束时，磨痕深度为两滑块和气缸测量了表面轮廓的方法（传感器曲率半径，5微米），垂直记录线配置的磨痕。采用微型磨损试验机（流动卫星通信系统）对硼化物的涂层耐磨损进行了评估，它是基于缩孔几

9、何效应。球的反转，在小磨料粒子的存在扁试样旋转产生一种强加在材料球面几何磨损陨石坑。基本上包括钻机，如图2所示，马氏体钢硬球，（半径为r = 12.7毫米，硬度hv 1000）对下研磨浆的调查样本轮换的存在（sic水悬浮颗粒浓度的初步规模4-5微米， 0.75克厘米-3），维护和地区的联系，通过一个缓慢的补充不断滴饲料（0.25立方厘米分钟-1）。图2 示意图球缩孔微量磨损试验机图3 多相硼化物涂层对铁截面的影响，显示出feb和fe2b层柱状形态，并沿裂纹优先在feb-fe2b单接口产生图4 测定的硬度通常两名硼化物涂层不同的区域的外部表面铁增长。涂层的区域内显示相当高的硬度值（文件编号2）。

10、（e）60米图5 x射线衍射谱（联合亩辐射）为在不同深度的渗铁被测样品层后，按平行层材料去除外部表面：（一）为-硼;（二）6米;（三）16米;（四）32米滑动距离（km）图6 磨损曲线硼铁，为了作比较，向其他表面处理的钢样的曲线，在不同的载荷值：（1）为5n和（b）25 n.图7 缩孔的球在从一个多相硼化物涂层外表面不同深度的方法确定的磨损率增长后，在铁层按层去除。一个0.2n接触载荷用和滑动速度0.05ms-1。对磨损试样所产生的球冠直径b测定的校准光学显微镜，而b值用于计算两个穿透深度h和磨损体积v：h b28r (1)zài x shèxiàn ynsh&#

11、232; fnx shì lìyòng jìsuànj jìnxíng kòngzhì de cè jio yí hé fúshè liánhé mv b464r (2)这里 br。如果磨损陨石坑深度低于涂料，一对散装物料的简单模型磨损厚度（等值的滑动磨损查德方程）可用于并导致磨损量为下面的等式v：v = ksn (3)其中s是总滑动球的距离相对于试样表面，n的正常负荷，钾的磨损系数或特定的磨损率。eq当量允许的磨损率。材料来计算每一组

12、实验中，每一层的揭露层技术方法将硼化物涂层每个部位都暴露在外。3 结果和讨论图3显示了典型的多相硼化物涂层微观结构对纯铁增长。feb和fe2b层和宣传沿裂缝柱状形态在feb-fe2b接口更好的扩散。对中碳钢生长在相同的热条件，表现了最大的涂层厚度和不太明显柱状形态，最大值和最小值厚度有很大不同。该涂层厚度是影响合金的（尤其是由铬）金属基体元素，可以修改输入硼化物晶格铁硼扩散活动。此外金属硼反应可以改变在对金属基体表面区域的组成发生（损耗或元素浓度）的修改，作为涉及合金元素再分配现象的结果。柱状接口已被解释为当地激烈的应力场和附近的晶格畸变的结果和针状核反应产物。feb-fe2b的接口的脆性反过

13、来归结于该地区强调诱导之间的两个铁硼化物热膨胀系数不同，以至于feb是它的三倍。在铁的硼化物之间的差别是相当大的弹性，对硼的价值是，通过对fe2b单显示的一半。图4显示两个相同的跨衡量的显微硬度的测量如图3一样。在大幅降低硬度是显示在涂层外部分的配置文件之一（另一个是由一位来自外部表面明显的距离开始）将被视为现实的，在前面提到的证据的最外层，几微米的硼化物涂层厚度地区晶体学是紊乱和易碎的。在诸如从外部表面距离的增加硬度下降要归功于硼化物和纯铁区的存在，即成为在实现试样的体积要大得多。高硬度涂层的内部区域显示（结构编号2）应注意。图5显示了x射线衍射在同一硼化物层不同深度的记录方式，在材料逐步消

14、除之后。feb（002）和fe2b（002）反射强度比硼化物粉末强得多。特别是，一个非常强烈的fe2b（002）峰值可以看出，即使在目前情况，硼铁被测样品的x射线衍射图，尽管在一个硼外层涂料的存在。在feb（002）和fe2b（002）峰的相对强度的硼化物逐步增加的涂层由一层薄按层材料去除进行了平行的外表面。因此，可以推断，在（002）两铁硼化物纹理经历的多相向内强化涂层。特别是对fe2b单子层内部是由所有与001硼化物晶体排列晶轴垂直构成导向的样品的表面。一个具体的研究，最近已给解释刻画择优取向的铁发生硼化变形的铁和钢的成长。研究的结论是对fe2b单第一晶体生长样品的外表面，金属表面之间的硼

15、化粒子的接触带开始，一个是因为一个最简单的形式存在的针状001的发展方向，与硼在体内扩散的路径更容易fe2b单重合为中心的四方晶格。对硼化物晶体生长作为一个覆盖面，增加了越来越多的障碍。因此，硼化物晶体的越来越多是被迫种植向内，因为在相关的硼化物的形成量的增加更加困难增长轨道。fe2b单向内的增长是比较容易，如果拉长硼化物晶体生长平行。因此，新的硼化物晶体的涂层形成金属界面的逐步被迫与他们成长001轴垂直于外表面，即相一致的样本中硼梯度，导致（002）择优取向的fe2b单上逐步实现与金属基体界面将加强。图6显示了在干摩擦条件下，硼钢磨损行为，在提交给其他样品表面的修改比较。根据负载（图6a中）

16、为5n，中间的行为是氮化钢之间的（差）和碳化钨钴（最佳），并具有可比性的，通过展示硬铬。磨损的斜率为多相层距曲线最初是高作为一个外，易碎区域的存在合理的结果，由无序晶体组成。逐步下降的斜坡下降到约5.3mkm1。根据负载（图6b型）25n，对硼钢的行为再次中间氮化之间的样品和卫生间的钴涂层样品，而硬铬行为是类似的氮化钢中显示的。磨损违背了硼钢艾斯坦斯最初曲线陡峭，符合市场预期。然后斜坡下降，可能由于硼化物晶体有序耐磨性高，最后也大大增加值达到43mkm1，然后因为磨损，没渗硼区铁所接触到的陶瓷材料。摩擦系数的硼钢，最初由低切外，涂层的无序地区显示实力，逐渐增加值大幅波动对低0.6左右，价值与涂

17、料的滑动对文献报道的比较钢铁及其他工程合金。值得一提的是，摩擦系数由0.5至低于0.1大幅下降，得到了硼低碳滑动针对空气中氮化硅球在室温下为5n和2钢4mms - 1揭露硼化物，涂层，空气750fb的3分钟的气氛。改善解释作为反应之间的空气和硼氧涂层效应，将高温曝光：第一，一硼氧化膜形成的，后来，在引起了硼酸润滑膜空气中的水分反应。一个硼化物涂层摩擦学性能更为详细的评估，获得通过测试其耐磨损性。如图7所示，事实上，磨损率表示为每单位距离磨损材料的数量和应用负载的单位是非常的，渗样本（pt.图1.7），由于外部，机械已经提到的存在易碎地区的硼化物涂层。磨损率大大降低（pt.图2.7）地区的内部，

18、在金相观察，发现由fb组成，并在较少fe2b程度。透过涂层会进一步向内，磨损率增加在fb - fe2b单界面图（pt. 3.7），并成为该地区最低的高度有序的晶体构成fe2b单（pt.图4.7 ）。然后，磨损率增加的地区所构成fe2b单柱和非渗硼铁（pt.图5. 7），更有甚者，当只有纯粹的，软铁提交磨损图（pt.图6.7）。指出的摩擦学行为的磨损率值图进行报道。 图7确认有必要向渗组件的表面处理程序，适用于消除外，抗差的硼化物涂层的一部分。此外，这也可能解释为什么一个有序和强硬的fe2b单是首选的高度强，一多相硼化物涂层，艰难，但是在feb-fe2b高压力的接口下容易过早失效。4结论多相硼化

19、物涂层提高铁的性能，结构钢是由一个feb硼外层和内层的fe2b单相构成的晶体与秩序的程度，这与外部表面不同深度所在地区不同。机械紧凑和耐磨性取决于此。该涂层的磨损率高，最初都在滑动和磨料条件下，因为一个无序晶体外，薄，易碎层的存在。然后，磨损率下降是因为受了硼晶体排列第一的反抗，然后对fe2b单相，直到达成一项内，非常紧凑的涂料地区的最低值由fe2b单高度有序的晶体组成。feb-fe2b接口在高应力状态下使硼化物的多相涂层摩擦学性能大大降低，导致成核和裂纹沿界面扩张，并伴随磨损碎片的形成。通过厚度球的手段，缩孔和层的层的方法对磨损率进行了测量，被证明是评估不同深度的多相涂层耐磨性有效途经。鸣谢

20、作者要感谢意大利冶金协会安德烈.加莱西先生在微观尺度磨损测试给予的支持。参考文献1 a.k. sinha, boriding (boronizing), in: heat treating (section: surface hardening of steel), vol. 4, asm handbook, 1999, pp. 437447.2 r. chatterjee-fischer, boriding and diffusion metallizing, in: t.s. sudarshan (ed.), surface modification technologies, marce

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24、andstrallerabstractpolyphase boride coatings constituted by an inner layer of fe2b and an outer layer of feb were thermochemically grown on iron and medium carbon steel by a pack cementation process. the tribological behaviour of borided samples was investigated under both slidingand abrasion testin

25、g conditions. considerably different values of wear rate were found in different regions of the coatings. the differences were explained on the basis of the crystallographic order of iron borides. the resistance to both types of wear was initially poor due to the presence on the coatings of a thin,

26、friable layer constituted by disordered crystals. then the resistance increased to a maximum value in regions constituted by compact, highly ordered crystals of fe2b. the resistance to dry sliding of borided samples was better than that displayed by samples submitted to alternative surface treatment

27、s (e.g. gas nitriding) and lower that that measured for awcco hard metal coating.© 2003 elsevier b.v. all rights reserved.keywords: boriding; iron; steel; sliding wear; abrasive wear; preferred orientations; crystallographic order; tribotesting1 introductiona rapid expansion of activities in th

28、e field of surface modification techniques has been promoted by the increasing demand for materials with satisfactory resistance to wear, corrosion or both. in many applications, in fact, the in-service life of components is determined by surface properties. in the important field of thermochemical

29、treatments of steels, based on diffusion of species such as carbon, nitrogen or boron, boriding is in a peculiar position. on one side, coatings constituted by iron borides thermochemically grown on steels generally display very high hardness, even in excess of 20 gpa, as well as high wear resistanc

30、e 1,2. borided steel components display excellent performance in several tribological applications in the mechanical engineering and automotive industries. it is worth noting that the best results are obtained by pack cementation, i.e. processes carried out using powder mixtures containing a boronis

31、ing component (e.g. b4c), an activator (usually kbf4) and eventually a diluent component added in order to control the boronising potential of the medium. however, as compared to gas phase treatments, industrial processes carried out with powders are: (i) more complicated, time consuming and expensi

32、ve, and (ii) less suited to process control and automation, this situation hindering an adequate diffusion of boriding treatments.efforts addressed to set up industrial gas boriding processes are in progress, with main problems concerning the control of both the processing conditions and composition

33、 and porosity of the boride layers. in particular, a lack of knowledge is recognised about the interaction mechanisms between plasma and metal surface. as an example, boride coatings produced on two medium carbon steels by plasma assisted chemical vapour deposition at 833k using a bcl3h2 gaseous mix

34、ture diluted with ar, were only few micrometers thick and contained in both cases a poorly adherent feb layer 3. on the other hand the wear performance of oil pump drive gears of an automotive engine, plasma borided in a similar gaseous mixture, were found comparable with those obtained with pack bo

35、ron cementation4. however, a post-boriding heat treatment was required to obtain single phase layers, i.e. coatings only constituted of the less hard but also less brittle iron boride fe2b 4. attempts to substitute the boron halide and diborane boron precursors with organic precursors allowed to gro

36、w single fe2b phase layers up to 10 _m thick on a medium carbon steel, any further growth being prevented by the unfavourable action displayed by carbon 5. the tribological behaviour of these boride layers was evaluated only by comparison with untreated samples. a lot of work has been carried out on

37、 the tribological behaviour and in particular on the wear resistance of borided steels of very different composition, investigated under very different testing conditions. the main interest has been focused on two peculiar characteristics of the boride coatings:(i) high hardness, that is expected to

38、 give a high wear resistance, and (ii) columnar morphology, that is required for a good adhesion between coating and substrate. less attention has been devoted to clarify the mechanisms of wear damage, and in particular to the role of crystallographic orientation of iron borides within the coating.

39、it is well known, in fact, that thermochemical boriding can give rise to iron borides fe2b (tetragonal) and feb (orthorhombic), both generally displaying a strong (0 0 2) preferred orientation 2. the texture strength is significantly influenced by the composition of the base alloy, as a consequence

40、of diffusion phenomena involving alloying elements that enter substitutionally the coating from the substrate and modify the properties of both coating and substrate 6. on the other hand, it has been pointed out that the outermost, few micrometers thick region of the boride coatings is crystallograp

41、hically disordered and, consequently, it should be removed from the borided component by means of a finishing procedure 7. the aim of the present work is to investigate the wear resistance of boride coatings produced on iron and steel by pack cementation and tested under both sliding and abrasive co

42、nditions, with particular regard to the influence of the crystallographic orientation of iron borides on the wear rate.2 experimental details2.1 materials and treatmentssheets of armco iron (99.9 wt.% pure) and a medium carbon steel (uni 38 nicrmo 4) were annealed at 1000 c under vacuum, surface fin

43、ished with a 600 grit sic emery paper and then borided at 850 c for 15 h using a powder mixture constituted by b4c (20 wt.%), kbf4 (10%) and sic (balance). pure iron was selected in order to investigate boride coating free from alloying elements diffused from the substrate. the composition of the bo

44、ronising medium is suitable to grow polyphase coatings, constituted by an inner layer of fe2b and an outer layer of feb.the borided samples were characterised by means of optical (om) and scanning electron microscopes (sem), x-ray diffraction analysis (xrd) and microhardness measurements (mhv). the

45、xrd analyses were performed using a computer-controlled goniometer and the co k_ radiation. the crystallographic texture of iron borides was evaluated at different depths from the external surface by gradually thinning the coating with the layer-by-layer removal technique. the microhardness measurem

46、ents were carried out through the thickness of the coatings on cross-sections prepared with the usual metallographic techniques, using a conventional vickers indenter and an applied load of 0.5 n. for comparative testing under sliding conditions, the medium carbon steel was also gas nitrided at 570

47、c (total treating depth 0.3 mm) or coated with a 10_m thick layer of hard chromium (hardness 6768 hrc). an m 35 tool steel (composition c 0.85 wt.%, cr 3.75 wt.%, mo 5.0 wt.%, w 6.10 wt.%, v 2.05 wt.%, co 5.0 wt.%) coated with a layer of hard metal (wc18%co, hardness 88 hra) deposited by the air pla

48、sma spray (aps) technique was selected as a reference, highly wear resistant material.2.2 tribological testsdry sliding tests were carried out using a computer controlled slider-on-cylinder tribometer (fig. 1). the stationary sliders were constituted by the material under investigation, in the form

49、of prismatic bars (5mm×5mm×50 mm). the counterfacing material was a ceramic coating consisting of al2o3 (87 wt.%) and tio2 (rockwell hardness hrd = 60, surface roughness ra = 0.5_m) deposited onto the rotating cylinder. the tests were carried out under applied loads of 5 and 25n and slidin

50、g speed of 0.18ms1, for sliding distances up to 5 km, at room temperature (2025 c), in laboratory air (relative humidity in the range 5060%). both friction resistance and system wear (i.e. cumulative wear of both slider and cylinder) were continuously measured by means of a bending load cell and a d

51、isplacement transducer, respectively, and were recorded as a function of the sliding distance. at the end of each test, wear scar depths were measured on both slider and cylinder by means of a stylus profilometer (pick-up curvature radius, 5 _m), recording line profiles perpendicularly to the wear s

52、car. the resistance of the boride coatings to abrasive wear was evaluated using a microscale abrasion tester (msat), which is based on a ball-cratering geometry 8,9. the rotation of a sphere against a flat specimen in the presence of small abrasive particles generates a wear crater with an imposed s

53、pherical geometry within the material. basically the rig consists, as shown in fig. 2, of a hard martensitic steel sphere (radius r = 12.7 mm, hardness hv 1000) rotating against the specimen under investigation in presence of an abrasive slurry (an aqueous suspension of sic particles 45 _m in size,

54、with an initial concentration of 0.75 g cm3), maintained and replenished at the contact region by a slow constant drip feed (0.25 cm3 min1).a contact load of 0.2n was used and the sliding speed was 0.05ms1. the diameter b of the spherical cap produced on the specimen by abrasion was measured with a

55、calibrated optical microscope, and the value of b was used to calculate both the penetration depth h and the wear volume v: h b2/8r (1)v b4/64r (2) where b r.if the depth of wear craters is lower than the thickness of the coating, a simple model for abrasive wear of bulk materials (equivalent to the

56、 archard equation for sliding wear) can be used and leads to the following equation for the wear volume v:v = ksn (3)where s is the total sliding distance of the sphere relative to the specimen surface, n the normal load, k the wear coefficient or specific wear rate. eq. (3) allows the wear rate of

57、the material to be calculated for each set of experiments, i.e. for each region of the boride coating exposed by the layer-by-layer method.3 results and discussionfig. 3 shows a typical microstructure of polyphase boride coatings grown on armco iron. the columnar morphology of both feb and fe2b layers and the crack propagated along the interface between the febfe2b interface should be noted. the coatings grown on medium carbon steel underthe same thermochemical conditions displayed lower values of maximum thickness