梯度WC增强的NiCrBSi合金涂层制备及性能研究

发布时间：2018-05-07 02:31

  本文选题：梯度 + 陶瓷增强复合涂层　； 参考：《华东理工大学》2017年硕士论文

【摘要】：通过真空钎焊技术,以柔性金属布形式制备的WC-NiCrBSi合金涂层具有许多优点,例如涂层内部致密,无裂纹、气孔现象;涂层与基体是冶金结合,结合强度高;真空氛围,无氧化、脱碳等污染杂质出现;涂层表面光洁,能应用于各种曲面结构的改性等。陶瓷/金属梯度材料因其一侧具有陶瓷材料的耐磨损、硬度高、耐高温性能,另一侧具有金属材料韧性高、强度高的优点。因此将钎焊技术和陶瓷梯度材料的结合会有重大应用价值。本文在真空钎焊工艺下制备了梯度WC陶瓷增强的NiCrBSi合金涂层,主要的研究内容和结果如下:对WC柔性金属布的成型配比进行了实验,研究发现,mWC:mP7FE在10-150范围内能够成型,当质量比小于10时,得到的金属布弹性低,质量比大于150时,金属布强度低易烂掉;对质量比在10-60范围内经过四次折叠辊压后的金属布进行了拉伸性能测试,研究发现随着质量比的增加断裂应变增加,质量比大于50后,断裂应变减小。进行了不同钎焊温度和保温时间下均匀WC增强的NiCrBSi合金涂层的拉伸性能和磨损性能测试,为制备梯度涂层做工艺参数方面的准备。研究发现,当保温时间为15min,钎焊温度在1000-1100℃范围变化时,在1080℃时磨损损失量最小为11.1mg;当钎焊温度为1080℃,保温时间在5-30min范围时,随着温度的增加拉伸性能逐渐升高加后降低,在保温时间为10℃时,涂层结合强度最高为230MPa。通过调整金属布中WC颗粒和NiCrBSi合金粉体积比,使不同层金属布中的合金粉体积比呈梯度变化,通过大量的实验和钎焊工艺参数的优化,得到四种不同梯度斜率的梯度WC增强NiCrBSi合金涂层。对四种不同梯度斜率的涂层试样进行了磨损性能的测试,研究了涂层梯度形式对涂层微观形貌、硬度和摩擦磨损性能的影响。随着涂层梯度斜率的增加,涂层的耐磨性能增加。当涂层梯度斜率较小时涂层的磨损损失失效机制为磨料磨损,当梯度斜率较大时为疲劳磨损失效。对四种不同梯度斜率的涂层和涂层/基体试样进行拉伸性能的实验,研究涂层的断裂机理。通过原位拉伸观察涂层/基体试样涂层表面裂纹从萌生到完全贯穿的全过程,发现裂纹萌生于WC颗粒及其附近应力集中的地方。随着涂层梯度斜率增加,涂层/基体断裂应变增加,贯穿裂纹数量略有增加;涂层断裂应变减小,能承受的拉伸强度减小,涂层为脆性断裂。
[Abstract]:Through vacuum brazing technology, WC-NiCrBSi alloy coating prepared in the form of flexible metal cloth has many advantages, such as dense coating, no crack, porosity phenomenon, metallurgical bonding between coating and substrate, high bonding strength, vacuum atmosphere and no oxidation. Pollution impurities such as decarbonization appear and the coating surface is smooth and can be used in modification of various surface structures. Ceramic / metal gradient material has the advantages of wear resistance, high hardness and high temperature resistance of ceramic material, and high toughness and strength of metal material on the other side. Therefore, the combination of brazing technology and ceramic gradient materials will have great application value. In this paper, gradient WC ceramic reinforced NiCrBSi alloy coatings were prepared by vacuum brazing. The main research contents and results were as follows: the forming ratio of WC flexible metal cloth was tested, and it was found that mWC: mP7FE could be formed in the range of 10-150. When the mass ratio is less than 10:00, the elasticity of the metal cloth is low, and when the mass ratio is greater than 150, the low strength of the metal cloth is easy to rot, and the tensile properties of the metal cloth after four fold roll pressing in the mass ratio of 10-60 are tested. It is found that the fracture strain increases with the increase of mass ratio, and decreases when mass ratio is greater than 50. The tensile and wear properties of NiCrBSi alloy coatings with uniform WC reinforcement at different brazing temperature and holding time were tested in order to prepare the process parameters for the preparation of gradient coatings. It is found that when the holding time is 15min and the brazing temperature varies from 1000-1100 鈩，

本文编号：1855013