【作者】 杨效田；

【导师】 王智平；

【作者基本信息】 兰州理工大学 ， 材料加工工程， 2012， 博士

【摘要】 Al含量超过Cu-Al合金共析点w(A1)=11.8%的高铝青铜合金材料具有较高的硬度、很好的减摩性能。课题组研究开发的Al质量分数达到14%的高铝铜合金材料具有很好的减摩耐磨性能和抗腐蚀性能,已成功应用于拉伸、冲压模具当中。但该材料性能较脆,作为整体材料应用,在使用的过程中容易发生崩裂等缺陷,并且作为整体材料使用成本较高。将该材料研制成粉体材料,并通过先进的涂层制备技术将其制备成表面保护涂层,对拓宽该材料的使用范围,实现工件表面保护和修复具有重要意义。另外,所研制的高铝铜合金粉体材料属于非自熔、易氧化的合金材料,对其的开发研究将对表面工程领域的深入发展产生重要影响。本文配置了一种w(Al)=14%的多元高铝铜合金材料,采用共装法一次熔炼、氯化物法化学精炼、预脱氧与终脱氧工艺方案联合使用的方法熔炼了合金熔体,通过双级耦合快凝低真空雾化制粉技术制备了该合金粉体材料。制备的粉体材料主要成分为w(Cu)=70%～80%,w(Al)=12%～16%,w(Fe)=2.0%～4.0%,其余为可调整的Mn,Ni, Co等微量元素。在3～8MPa雾化压力下得到中小粒度的粉体能够到达70%以上,制备的粉体具有23.9/s·(50g)-1的较高流动性和3.56/g·cm-3的较低松装密度,粉体的维氏显微硬度平均值达到384HV。所制备的合金粉体的熔点为1048℃,材料属于软磁性材料,初始磁导率约为μi=1.24。提出了一种超音速等离子-感应重熔复合技术在45#钢基体表面制备优良高铝青铜合金材料涂层的方法。首先,通过超音速等离子喷涂技术制备了不同粒度的纯高铝青铜合金粉体涂层。借助X射线衍射仪(XRD)、电子探针(EPMA).场发射扫描电子显微镜(FEGSEM)及能谱仪(EDS)、Image-pro plus图像分析软件、Jade5.0软件等分析研究了制备的纯高铝青铜合金粉体涂层的组织结构、物相组成及相结构分布、缺陷率、以及涂层的相关力学性能,得出了最佳的喷涂粉体粒度。研究发现,采用400目以上的超细粉体材料制备的涂层组织结构致密、元素偏析程度较低、成分分布均匀、界面结合状况良好。涂层中存在的缺陷率和缺陷平均面积随着喷涂粉体粒度的增大而降低,400目以上粉体喷涂层组织微观缺陷率已降低到1.27%的相当低水平,缺陷平均面积0.40μ m2。400目以上的超细高铝青铜合金粉体具有更好地适应超音速等离子喷涂制备涂层的能力。其次,在得出的最佳粉体粒度中(400目以上)加入不同含量的稀土粉体元素Ce,经过混合后制备稀土改性的高铝青铜合金粉体材料涂层。通过相关组织结构和性能研究后,得出了最佳的稀土加入量。研究发现：微量稀土元素加入对喷涂层组织结构产生重要影响,随着稀土元素加入量的增加,晶粒表现得越来越细化、组织结构表现得更加细密均匀、界面结合状态明显改善。微量元素稀土的加入具有抑制合金成份偏析的作用,改变了涂层组织相的分布形式,涂层组织由原来的非平衡凝固转变为平衡凝固方式。在稀土加入量超过0.4%后,涂层的缺陷率明显减小,低于未加入稀土前的涂层缺陷率。微量稀土元素的加入使涂层硬度降低、综合力学性能得到提高、涂层硬度性能分散性减小。当其含量达到0.55%时,对性能分散度影响不大。得出最佳的稀土加入量为0.4%-0.55%之间。最后,对稀土加入量为0.55%的高铝青铜合金粉体涂层采用感应重熔处理技术进行涂层优化再制备。研究发现,经过稀土改性、感应重熔处理后的涂层组织结构致密度明显提高、缺陷率明显降低,结合状况得到大大改善。经过感应重熔后的涂层在界面处出现了一条约为10～15μm的白亮结合带,说明涂层与基体经过感应重熔后形成了冶金结合,这大大提高了涂层与基体的结合强度,使涂层相对于感应前剪切强度提高了12.7倍。感应重熔能使涂层中大面积的缺陷转化为以分散的小尺寸形式存在。减小了缺陷的局部集中对涂层性能产生的不利影响。感应重熔处理后,使涂层硬度值略有回升,并使硬度性能分散性进一步降低。在MMW-1万能摩擦磨损试验机上分别对纯高铝青铜合金喷涂层、稀土改性喷涂层和感应重熔后涂层的耐磨性能进行测试。结果表明：三种涂层在干摩擦条件下的摩擦系数都处在一个相对较低的水平,摩擦系数均小于0.20。540N高载荷时,摩擦系数均只有100N低载荷时的1/10左右,说明涂层具有承受高载荷摩擦磨损的能力。感应重熔后涂层摩擦系数明显低于感应前的涂层,感应重熔处理后的涂层具有更好地承受高载荷耐磨损能力。三种涂层的磨损机理基本相似,主要以磨粒磨损和粘着磨损为主,但不同载荷下的磨损形式略有不同。超音速等离子喷涂的纯高铝青铜合金粉体涂层在低载下以轻微的刮擦为主,高载荷下呈现明显的磨粒磨损特征,局部有明显的黏着及塑性变形痕迹。稀土改性的涂层在低载荷情况下已经发生了塑性变形,但磨痕形貌均匀,表现为磨粒磨损特征,高载荷下涂层表面的磨痕排列非常规整,出现较深较窄的犁沟,犁沟边缘也看不到舌状的、隆起的特征,主要表现为磨粒磨损形式。感应重熔处理后的涂层,在低载荷下为刮擦磨损和磨粒磨损为主,随着载荷的增加主要表现为磨粒磨损的形式,磨痕清晰、规整,显示出了更好的耐磨性能以及摩擦性能随载荷变化的稳定性。更多还原

【Abstract】 High aluminum bronze alloy material of Al content more than11.8%which is Cu-Al alloy eutectoid point possess high hardness, good antifriction performance. A kind of high aluminum bronze of w (Al)=14%has been developed successfully by our research group, which has very good antifrictionability, wear resistance and corrosion resistance performance, and has been successfully applied to stretch die and stamping die.But the material performance is brittle, and it has the defects such as cracking and high cost as a whole material application. Should this material be developed to powders, and be prepared to surface protection coating of the matrix by advanced coating preparation technologies, it has the important meaning to broaden the scope of the use of material and to realize the surface protection and repair of workpiece. In addition, because the high aluminum bronze alloy powders not belong to the self-fluxing and is easy oxidation materials, the development research will have an important impact on the surface engineering development further.In this paper,a multiple high aluminum copper alloy materials of w(Al)=14%was configured and smelted by the combined scheme use of common pack a smelting, chemical refining by chloride, preliminary deoxidizing and final deoxygenation process. The alloy powders materials was prepared by the double-stage coupled and fast-setting of low vacuum atomized powder preparation technology. The main composition of the material is w(Cu)=70%～80%,w(Al)=12%～16%,w(Fe)=2.0%～4.0%,and the other trace elements such as Mn, Ni, Co, which is adjustable.The medium and small size of the powders more than70%can been achieved in the atomization pressure of3～8Mpa, and the liquidity of the powders is high to23.9/s.(50g)-1, the apparent density is low to3.56/g.cm-3and the average vickers microhardness reached384HV. The melting point of the alloy powders is1048℃, and the material belong to the soft magnetic materials, its initial permeability about μi=1.24.A kind coating preparation method of supersonic plasma-induction remelting composite technology was put forward to prepare high aluminum bronze alloy material coating in45#steel matrix surface.First of all,the powders coating of different particle size of high pure aluminum copper alloy was prepared through the supersonic plasma spraying technique.The X-ray diffraction (XRD), electron probe (EPMA), field emission scanning electron microscopy (FEGSEM) and spectrometer (EDS),image-proplus analysis software, Jade5.0software were used to analysis structure, physical phase composition,phase structure distribution, defect rate, and related mechanical properties of pure high aluminum bronze alloy powder coatings. At last,the best spraying powders particle size was achieved.The study found that the coating structure compact, the element segregation degree is low, and the component distribution uniformity, and the interface bonding is good prepared by super fine powders of surpassing400mesh.The defect rate and defect average area existed in the coating decreased with spraying powders granularity increase, and the defect rate has been reduced to the quite low level about1.27%using the more than400mesh powders, at the same time, the defect average area is0.40μm2. It is thus clear that the super fine aluminium bronze alloy powders of more than400mesh has better adapt ability to prepare the supersonic plasma spraying coating.Secondly, the different content of rare earth element Ce powders was joined to the best particle size powders(more than400meshes)of high aluminum bronze alloy, and the modified high aluminum bronze alloy powders coating was preparated after mixed rare earth Ce.The best addition amount of rare earth was achieved through the related organization structure and performance research.The results showed that the joined trace rare earth elements has a significant influence to the spraying coating organization structure,whose grain size is more refined, the organization structure is more fine uniform,and interface bonding status is markedly improved with the increase of the addition amount of rare earth elements. The trace rare earth elements can inhibit composition segregation of alloy, change the phase distribution form of coating, making the organization structure of the coating form from the non-equilibrium mode into equilibrium mode in the process of solidification.The defect rate of the coating reduced significantly when the rare earth was added to more than0.4%,which is less than the coating before adding rare earth. The coating hardness is reduced after added rare earth elements, accordingly, the comprehensive mechanics performance is improved, and the dispersion performance of the coating hardness is decreased. When the content of Ce is0.55%, it is not obvious to the hardness dispersion performance of the coating. So,the result can be concluded that the best addition amount of rare earth is between0.4%and0.55%.Finally, the high aluminum bronze alloy powders coating added the rare earth0.55%was remelted using induction remelting treatment technique for the coating optimization.The result showed that the density of the coating structure is obviously improved and the defect rate of the coating is decreased by rare earth modification and induction remelting process,and the combining state is greatly improved, forming a metallurgical bonding appeared white light about10～15μm in the interface place, which improve greatly the bonding strength of the coating and substrate, making the shear strength is improved12.7times relative to the coating before induction. The induction remelting can make coating defect change from large size into the small size, reducing the bad effect of the defect of local concentration on the coating performance.The induction remelting treatment make the coating hardness value slightly rebounded, and hardness dispersion performance reduce further.The wear-resisting performance was tested about the pure high aluminum bronze alloy coating, rare earth modification coating and induction remelting coating by the MMW-1universal friction and wear test machine.The results showed that the friction coefficient of the three kinds of coatings are all in a relatively low level in the dry friction condition, which is less than0.20.The coefficient of friction under high load540N is only1/10of low load100N, indicating the coating has the ability to bear friction and wear under high load. The friction coefficient of the coating after induction remelting is significantly lower than the coating before induction remelting, indicating the coating by induction remelting process has better wear resistance ability under high load.The wear mechanism are basic similar about the three kinds of coatings, which is mainly abrasive wear and adhesive wear, but has slightly different form under different load. The pure high aluminum bronze alloy powders coating made supersonic plasma spraying show the minor scratches in low load,but the abrasive wear characteristics is obvious under the high load, and have obvious adhesion and plastic deformation trace in the local. The coating through rare earth modification have occurred plastic deformation in low load, but the grinding crack morphology is uniform, having the abrasive wear characteristics.Under high load, the arrangement of surface grinding crack is very neat, appearing more deeply and more narrow furrow, and furrow edge can’t see lorate and hunched characteristics, indicating abrasive wear form mainly. The coating after induction remelting is given priority to scart wear and abrasive wear in low load, but the form show abrasive wear mainly along with the load increase, whose grinding mark is clear and neat, showing a better wear resistance and the stability of friction performance with the load change.更多还原