V-EPC制备铁基表面耐磨复合材料

【作者】 李祖来；

【导师】 周荣；

【作者基本信息】 昆明理工大学 ， 材料加工工程， 2004， 硕士

【摘要】 论文采用V-EPC铸渗法成功制备了低铬铸铁、灰铁基WC颗粒增强表面复合材料，此工艺复合效果好，复合材料尺寸精度高，表面质量好。最适合于该工艺的耐火涂料配方为：100％石英砂；4％钠质膨润土；3％Na₂CO₃（占膨润土量）；2.5％白乳胶：0.5％CMC；0.05％十二烷基苯磺酸钠：0.02％正辛醇。适合该工艺的颗粒粘结剂为质量分数为6％的PVA水溶液，最好的浇注方式为底注，并且在铸渗层合金粉末中不使用NaF熔剂。WC在复合层内分布均匀，无聚集成团现象，过渡层平缓。基材与铸渗层之间无夹渣或气孔缺陷，为冶金结合。在铸渗过程中，母液往铸渗层渗透能力很强，合金元素向基材也有扩散，但量很少。复合层组织为：WC、W₂C、屈氏体、M₇C₃、M₂₃C₆、M₆C、M₁₂C等碳化物。 论文研究了浇注温度、抽气时间、WC颗粒大小、WC体积分数、壁厚、基材等因素对复合材料复合层表面质量的影响规律。尺寸精度研究结果表明：复合位置为底面时尺寸精度最高，局部壁厚公差等级达到CT5～8级，复合位置为侧面时较差，顶面时最差。同时还得出，随着WC体积分数的减小，尺寸精度有所提高。但总体上来看，铸件表面涂覆的颗粒层对V-EPC铸渗法制备的复合材料铸件尺寸精度影响不大，复合材料铸件的尺寸精度仍属较高水平，可以满足承受磨料磨损的铸件对精度的需要，对要求不太高的零件甚至可以直接使用。 论文还成功设计、制备了一台三体磨料磨损实验机，并做了三体磨料磨损实验机的重现性实验，实验结果表明，本实验机的测试性能是可靠的。磨损试验结果表明：复合材料的三体磨料磨损性能与高铬铸铁相比有明显地提高，最高可以提高到8.65倍，且随着载荷和WC颗粒体积分数的增大，复合材料耐磨性呈升高趋势。磨损机理为WC对周围组织的屏蔽作用，即“阴影效应”，失效方式为WC颗粒因疲劳而片状剥落。更多还原

【Abstract】 With V-EPC casting-penetrating technologies, WC particles reinforced low chromium cast iron and HT300 steel matrix surface-layer composites were successfully gained in the thesis. The casting process was optimized, the composites obtained have a high dimension precision and good surface quality . The sound coating for EPC is composed of: 100 percent of quartz sand, 4 percent of Na-sulfuryl bentonite, 3 percent of Na2CO3 (of Na-sulfuryl bentonite), 2.5 percent of white-latex, 0.5 percent of CMC, 0.05 percent of twelve alkyl phenyl sulfonic Natrium, 0.02 percent of ortho octahydrin, and the binder is 6%PVA, NaF is except, the perfect position of pouring is at the bottom of casting. WC is even in composites. The binding between composites layer and matrix is excellent, which is matellurgical binding. Between the matrix and composites has an even interface area with the substrate, with good bonding strength. During the process of composite,it is mainly the osmosis of iron liquid ,and alloying element also osmosizes to matrix ,but the quantity is very little. The matrix structure of composition is WC, W2C, M7C3, M23C6, M6C, M12C carbide and Troostite.The paper study the influence regularity for the surface quality of composite on pouring temperature, extraction time, WC particle size, WC volume fraction, parietes thickness, base material , and so on. The dimension precision study indicate when the position of pouring is at the bottom of casting, the dimension precision is good, the grade is CT5 to CT8, when at the side face of casting, the dimension precision is average,and when at the top of casting , the dimension precision is difference. Atthe same time, the dimension precision increases with diminution of WC volume fraction. But from the massing, the effect on the dimension precision of composites using V-EPC for particle layer coated in casting surface is little , and the dimension precision remain with high level which can satisfy the need on precision for casting resisting abrasive wear and some castings of needing low precision even directly is used.The thesis designed successfully and produced a three-body abrasive wear tester, and conduct reproducibility experiment. The experiment resultindicate the tester exhibited good reproducibility. The wear experiment result indicate three-body abrasive wear performance is increased significantly , which increased upmost 7.65 times, compared with high chromium cast iron. And the abrasive wear performance of composites is increased with accretion of stress and WC volume fraction, abrasive wear mechanism is shield of WC to other organization, shade effect, and failure patter is flaky exfoliation of WC for fatigue.更多还原