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1、南京航空航天大学硕士学位论文 I摘摘 要要 合金粉块碳弧堆焊是一种低成本，高效率的堆焊方法，但存在堆焊层成形不良的问题。硼和硅可使合金具有自熔性，有助于改善堆焊层成形并提高耐磨性。本文通过向 Fe-Cr-C 合金中添加硼铁和硅铁，从铺展性、表面平整度、表面缺陷情况和边缘平直度等四个方面分析研究了硼和硅对成形的影响规律。研究表明：向合金中单独加入适量硼铁和硅铁或联合加入硼铁和硅铁都可有效改善堆焊层成形。随合金中硼、硅含量增加，堆焊层铺展性提高，能与母材润湿良好，表面趋于平整，边界趋于平直，但过高的硼、硅含量下堆焊层易产生裂纹。 本文又通过磨粒磨损试验、硬度测试、磨损形貌分析、金相观察、显微硬度测
2、试、扫描电镜能谱分析和X射线衍射物相分析研究了硼和硅对堆焊层组织与耐磨性的影响规律。 结果表明：向合金中加入适量的硼可以显著提高堆焊层耐磨性，随着硼含量的增加，组织中硬质相数量增多，颗粒细化，分布弥散，且硬质相硬度提高，因此堆焊层硬度持续增加，耐磨粒磨损性能随之提高；但硼加入过多会形成网状组织，增大组织脆性，在磨损时脆性剥落情况加重，导致耐磨性下降。向合金中添加少量的硅可起到一定的固溶强化作用，在一定程度上提高耐磨性；但是随着合金硅含量增加组织脆性增大，裂纹和破碎剥落倾向加剧，耐磨性急剧下降。向合金中同时加入硼和硅对耐磨性的影响与单独加硼、硅的规律相似。 综合成形与耐磨性来看，向合金中单独加入
3、 4.11%硼，或同时加入 4.11%硼、3.86%硅时，可使堆焊层兼具良好的成形与耐磨性。 关键词：关键词：合金粉块，碳弧堆焊，硼，硅，堆焊层成形，耐磨性 南京航空航天大学硕士学位论文 IIIABSTRACT Carbon arc hardfacing with alloy power is a low cost and high efficiency hardfacing method. However, it is difficult to obtain a good shape after hardfacing. B and Si are the main elements of Se
4、lf-fluxing alloys, which could possibly improve the shape and wear-resisting property of hardfacing layer. By adding ferroboron and ferrosilicon into the Fe-Cr-C alloy and evaluating various features such as the spreading property, smoothness, surface defects, flatness of edge of the hardfacing laye
5、rs, the paper systematically studies that how B and Si influence the shape and wear-resisting property of the carbon arc hardfacing layer. It is found that the shape of the hardfacing layer could be improved effectively by either adding ferroboron/ferrosilicon alone or both of them into the alloys.
6、With proper content of B and Si the spreading property can be improved greatly , the layer could wet the base metal well, the surface of the layer appears to be smoother and the edge of the layer tends to be flatter. However, it tends to crack with excessive content of either B or Si. Moreover, the
7、paper further studies the wear-resisting property and microstructure of the layers with different B and Si contents by means of grain-abrasion testing, hardness testing, wear morphology analyzing, microstructure observation, microhardness testing, scanning electron microscope energy spectrum analysi
8、s and X ray diffraction analysis. The results reveal that the wear-resisting property of the surfacing layers is improved significantly by adding B into the alloy. With B content increasing, the number of the hard phases raised, the hard phases became smaller, distributed homogeneously, the microhar
9、dness of the hard phases increased, the hardness of hardfacing layer increased and the abrasive wear-resisting property improved correspondingly. However, the network structure tends to appear with excessive B content. It may raise the brittleness of the microstructure and lead to brittle fracture a
10、nd spell, which may result in the decreasing of wear-resisting property. A small Si content plays the role of solution strengthening and improves the wear-resisting property to a certain extent. But with Si content increasing, brittleness of the microstructure increases, crack and spelling tends to
11、appear, which may cause the wear-resisting property of hardfacing layer dropping greatly. The rule of adding both B and Si into the alloy appears to have the similar effect as adding either of them. Considering both the shape and wear-resisting property of the layer, adding 4.11% B alone or 4.11% B
12、and 3.86% Si simultaneously into the alloys, the layers could be obtained with good shape and wear-resisting property. 合金粉块碳弧堆焊层成形与耐磨性研究 IV Key word: alloy power block， Carbon arc hardfacing， Boron， Silicon， shape of the hardfacing layer，wear-resisting property 南京航空航天大学硕士学位论文 VII图表清单图表清单 图 1.1 合金粉块.4 图 2.1 试验方案流程示意图.12 图 2.2 合金粉块制备工艺流程.13 图 2.3 制备粉块的模具和木槌.13 图 2.4 TransPuls Synergic 4000 Fronius 数字化焊机.14 图 2.5 自制磨粒磨损试验机.16 图 2.6 -300 金相显微镜.17 图 2.7 Quanta200 型扫描电子显微镜 .18 图 3.1 试验室制备的合金粉块.19 图 3.2 不同焊接电流下的堆焊层形貌.20 图 3.3 运弧方式示意图.21 图 4.1 含硼堆焊层实际成形.
