【作者】 苗耀新；

【导师】 任露泉； 邱小明；

【作者基本信息】 吉林大学 ， 农业机械化工程， 2004， 硕士

【摘要】 在工农业生产中，因磨损而造成的材料消耗、能源消耗成为制约生产发展的严重障碍之一，在各种磨损中磨粒磨损约占磨损总量的50%。目前，通过在部件易磨损部位表面形成耐磨复合层材料，已成为提高部件耐磨性的一个重要手段。目前制备具备一定工程厚度要求的耐磨复合层主要有堆焊、钎焊、激光熔覆、铸造表面合金化、粉末冶金等几种方法，通过这些方法能够在部件表面制备具有高耐磨性的复合材料，从而增强部件表面的耐磨性，提高部件的使用寿命。本研究受到某些土壤动物体表非光滑几何特征具有减磨、耐磨特性的启示，应用放电等离子烧结(SPS)工艺，选取具有优良塑性的Cu基合金作为复合层基体，硬质点WC颗粒作为增强相，在碳钢表面形成WC\ Cu基合金耐磨复合层，在两体静载荷磨粒磨损条件下，高硬度、耐磨WC颗粒镶嵌在高塑性的Cu基合金基体中，共同抵抗磨粒的磨削，表现出某些土壤动物体表非光滑几何特征所具备的优良减磨、耐磨特性。SPS是一种快速烧结新工艺，将瞬间、断续、高能脉冲电流通入装有粉末的模具上，在粉末颗粒间即可产生等离子放电,导致粉末的净化、活化、均化等效应。SPS具有加热均匀、烧结温度低，烧结时间短，可获得细小、均匀的组织、高致密度材<WP=60>料的特点，可以在碳钢表面形成厚度由几毫米到十几毫米任意调节的复合层。目前，应用SPS工艺制备WC\ Cu基合金非光滑耐磨复合层，未见其它研究报道，本文具体开展如下研究工作：首先利用正交实验法优化放电等离子烧结制备复合层的的工艺参数，确定具有较佳耐磨性的复合层的基体合金种类以及WC硬质颗粒的含量和几何尺寸。优化结果为：合适的SPS工艺参数为：轴向烧结压力：30Mpa， 以150℃/分钟的加热速度将模具升温到700℃，保温5分钟。耐磨性较佳的材料组分为：Cu基40合金粉，WC颗粒粒度为45~55目，质量百分含量为50%。其次，对复合层的组织结构进行研究，结果表明：（1）应用放电等离子烧结工艺制备的WC\ Cu基合金耐磨复合层强化低碳钢试样，通过光学显微镜观察，在复合层中，WC颗粒均匀分布于铜基合金基体中，铜基合金组织了晶粒细小、均匀，与WC颗粒结合紧密，复合层中未见明显孔隙。（2）在复合层与碳钢构成的系统中，存在着WC颗粒与基体合金界面和两种界面基体合金形成清晰可见的过度层，铜锌合金充满于之间，与WC颗粒接触界面上未见孔隙，另外，复合层基体合金与低碳钢结合界面也清晰可见，二者之间也存在明显的过度层，扫描电镜能谱分析表明以上两种结合界面均有一定元素扩散，有轻微的冶金反应。（3）通过对复合层进行X射线衍射分析，结果表明复合层的物相组成包括：WC、WC2、锌在铜中固溶体α相以及电子化合物CuZn为基的固溶体β相。最后，本文对WC\ Cu基合金非光滑耐磨复合层的磨粒磨损行为进行了深入研究，并队其耐磨机理进行探讨，得到以下结论：（1）放电等离子烧结工艺制备的WC\ Cu基合金非光滑耐磨复合层，WC颗粒粒度为45~55目，质量百分含量在小于50%范围内，复合层的孔隙率在5%以内，复合层致密性好，在这个范围内，随着WC颗粒百分含量的增加，复合层耐<WP=61>磨粒磨损性能增强，WC颗粒百分含量为50%时，复合层的耐磨性为淬火45钢的16倍。（2）不同目数、WC质量百分含量为50%的WC/Cu基复合层，在磨粒磨损试验中，在磨粒尺寸等磨损条件一定的情况下，复合层耐磨性随载荷的增加而降低；在载荷等磨损条件一定的情况下，复合层耐磨性随磨粒尺寸的增加而降低，磨粒的粒度对复合层的磨粒磨损性能的影响存在一临界值，本研究中此临界值的范围为74~100μm。（3）WC颗粒质量百分数固定为50%，WC颗粒粒度为45~55目的复合层的耐磨粒磨损性能高于WC颗粒粒度为60~75目和80~100目的复合层，说明SPS工艺制备颗粒增强复合材料，在一定程度上能够克服硬质颗粒粒度大、含量高而导致复合层致密性差、耐磨性低的缺陷。（4）WC/Cu基合金非光滑耐磨复合层的磨粒磨损失效形式表现为，铜锌合金基体受到磨粒的犁削后在表面产生的犁沟以及WC硬质颗粒的疲劳断裂和整体脱落。（5）WC/Cu基复合层中组织细小、均匀的铜锌合金基体具有优良的塑性，并与硬质颗粒WC之间形成结合性能良好的界面，在磨粒磨损过程中，起到稳固硬质颗粒，吸收能量，减缓冲击的作用。 （6）WC/Cu基复合层中高硬度、高强度的WC颗粒突出在复合材料表面承受载荷，阻止了磨粒的挤压和刺入，并使磨粒棱角钝化，减轻或阻止磨粒对材料表面的切削。（7）具有非光滑结构单元（WC颗粒）的复合层表面使参与复合材料磨损的磨粒改变运动方向，使之由滑动变为滚动，产生有利于减小切向力的法向微振动，减少磨粒和复合材料的接触面积和作用时间，从而大大减轻了磨粒对复合材料表面的损伤。以上研究表明通过放电等离子烧结工艺制备的WC/Cu基合金非光滑耐磨<WP=62>复合层，由于采用先进的制备工艺，可以获得组织性能优异的复合层材料，复合层在磨损过程中形成的非光滑表面，具有显著的耐磨特性。该材料用于强化低应力磨粒磨损工况条件下的部件表面，具有广泛的应用前景。更多还原

【Abstract】 The Waste of materials and energy sources has become a serious obstacle in modern industry and agriculture development. In all kinds of wear styles, the abrasive wear nearly occupies 50% of wear total quantity. At present the preparation of wear-resistant composite layer on components has become an important measure to improve wear-resistant of machinery parts.At present, the measures preparing wear-resistant composite coating with a certain engineering thickness include overlaying,brazing,laser cladding,cast-in-place surface alloying and powder metallurgy,etc. By using these coating techniques, it is impossible to prepare composites coatings with high wear resistance on components. The coatings improve the wear-resistant of components surface and make components have longer service life.The unsmoothed characteristics of some living beings in soil have wear reduction and wear resistance function . The research benefits the revelation that a tungsten carbide(WC) reinforced Cu-base alloy wear-resistant composite coating was produced on mild steel by spark plasma sintering (SPS).Under the condition of two bodies abrasive wear ,the coating with the structure that hight hardness and good wear resistance WC particles embedding in tough fine Cu-base alloy matrix resist the abrasion wear and manifest the good wear reduction and wear resistance properties that the unsmoothed bodysurface of some living beings in soil have.SPS is a new process of rapid sintering technics. The instantaneous, intermittent and high-powered electric pulse is applied in die where the powders are put in. The high-powered electric pulse can generate plasma among powder particles,resulting in cleaning effect,activation effect and uniformization effect ,etc. It’s properties include uniform heat up， low sintering temperature and short sintering time . It can produce high compact materials with fine and uniform structure. By using this technique, it is impossible to prepare composite coating with the adjusted arbitrarily thickness. At present ,there were many studies on the wear-resistant composite coatings,but no research groups besides the author’s research group concerned about the WC/Cu–base alloy wear-resistant composite produced by using SPS. The following research works have been conducted in this paper. Firstly, the normal test was utilized for optimization of technique parameters of SPS , the weight fraction and dimension of reinforcing particles in order to obtain <WP=64>better wear resistance. The optimal results of reinforcing particles weight fraction and dimension and technique parameters have been obtained as following: WC particles weight fraction of 50%, WC particle dimension of 45-55 mesh, sintering pressure of 30Mpa, perform preheated temperature of 700℃,heat up speed of 150℃ per minitue, heat preservation for 5 minitues.Secondly, the structure of the coating was investigated . The research results have been obtained as following.(1) In the specimen that WC/Cu-base alloy composite coating reinforcing mild steel , The optial micrstructure of the composite coating indicated that WC particles are distributed homogeneously in the Cu-base alloy matrix and the crystal grains of the Cu-base alloy are fine and uniform . WC particles combine strongly with the alloy matrix. There no obvious pore in the coating.(2) There exists two interfaces in the coating-substrate system. One is the inner interface between WC and Cu-base alloy in the coating,the other is the coating/substrate(mild steel) interface.With EDS(SEM) analyses, the elemental distributions across the interfaces were investigated. The research results show that elemental diffusion and light metallurgy action was occurred in the interfaces.（3）The results of XRD examinations manifest that the phases of the coating consist of WC ,WC2 , αphases-the solution that Zn dissolve in Cu andβphases-CuZn compound .Lastly, the abrasive wear properties of the composite coating and the wear-resistant mechanism were investigated .The research results have been obtain as更多还原