【作者】 李颖；

【导师】 杜忠泽； 符寒光；

【作者基本信息】 西安建筑科技大学 ， 材料加工工程， 2014， 硕士

【摘要】 铬是耐磨金属材料中应用非常广泛的合金元素，钢中加入适当的Cr可以使其具有高的硬度和耐磨、耐高温、耐腐蚀性能，但是影响Fe-Cr-B合金组织与性能的主要因子是硼、碳元素，而非Cr元素，因此，降低Fe-Cr-B合金中Cr的添加量不仅对组织和性能无太大影响，而且能大大降低合金成本。本文研究了含0.3%C、1.5%B和0~15%Cr的Fe-Cr-B合金，观察Cr含量对合金显微组织与相组成的影响，并测量不同Cr含量Fe-Cr-B合金的硬度和耐磨性能，分析硬度与耐磨性能的变化趋势，从而优化合金中铬的添加量。试验结果表明：随Cr含量的增加，铸态Fe-Cr-B合金基体由珠光体+铁素体向马氏体转变，说明Cr增加了基体的淬透性；而晶界硼碳化合物则随Cr含量的增加，由Fe3(B, C)转变为(Fe, Cr)3(B, C)，且当Cr含量超过10%时形成新的Cr3C2型碳化物。合金经淬火+回火处理后，奥氏体基体转变为回火马氏体，硼碳化合物相未发生分解，但在1050℃淬火后出现熔断、颗粒化现象。铸态Fe-Cr-B合金的硬度随Cr含量的增加显著增加，但当Cr＞10%时，硬度略微下降，这是因为Cr3C2的硬度略低于Fe2B，而随着Cr含量的增加，Cr3C2的体积分数增加，降低了合金硬质相的硬度。将Fe-Cr-B合金经1050℃油淬+回火处理后，发现含铬Fe-Cr-B合金硬度高于无铬Fe-B合金，且无铬Fe-B合金随回火温度的上升硬度快速下降，含铬Fe-Cr-B合金则在高于450℃回火时硬度迅速下降。试验利用MLD-10型动载磨料磨损试验机，对标准试样Cr12MoV钢和经过1050℃油淬+（250℃、350℃、400℃、450℃和550℃）回火处理的Fe-Cr-B合金进行耐磨测试，测试结果发现：当Cr＜6%时，Fe-Cr-B合金的耐磨性低于Cr12MoV钢；当6%≤Cr≤15%时，Fe-Cr-B合金的耐磨性能较Cr12MoV钢略高或持平。随回火温度的升高，Fe-Cr-B合金的耐磨性能下降，但在450℃回火时耐磨性出现回升，随后继续下降。Fe-Cr-B合金的主要磨损机制为凿削式磨粒磨损和塑性变形磨粒磨损，脆性剥落不明显，因而，Fe-Cr-B合金具有很好的耐磨性能。更多还原

【Abstract】 Chromium is a kind of alloying element extensively used in wear resistant metalmaterials. When adding proper addition of Cr, the steel can obtain the features of highhardness, good wear resistance, high-temperature resistance and good corrosionresistance. But in Fe-Cr-B alloy, the main influence factor on structure and propertiesare boron and carbon, rather than Cr. Therefore, reducing the content of Cr in Fe-Cr-Balloy not only has little effect on structure and properties, but also can greatly reducesthe cost of alloy.This paper studies the Fe-Cr-B alloy which contains0.3%C,1.5%, B and0~15%Cr. In order to reduce the content of Cr, we observe the effect of Cr content onmicrostructure and phase composition of alloy, measure the hardness and wearresistance of Fe-Cr-B alloys, and analyze its change tendency. Experiment results showthat: as the content of Cr increased, the as-cast of Fe-Cr-B alloy transforms frompearlite and ferrite matrix to martensite matrix, this illustrates the addition of Cr canimprove the baldness of matrix; the boron carbide compound changes from Fe3(B, C) to(Fe, Cr)3(B, C) with the increase of Cr, and it forms Cr3C2carbide when the content ofCr is over10%. After quenching and tempering, austenitic matrix transforms totempered-martensite, boron carbide compound isn’t resolved, but it happens to melt andgranulate after quenching at1050℃.The hardness of the as-cast Fe-Cr-B alloy increases with the content of Cr, but thehardness declines slightly when Cr content is more than10%, this is because thehardness of Cr3C2is slightly below Fe2B, and Cr3C2volume fraction is more and morewith the content of Cr increase, so the hardness of hard phase is reduced. Inexperimenting we find out that, after oil quenched at1050℃and tempered, the hardness of Fe-Cr-B alloy with Cr is higher than Fe-B alloy without Cr, and the latter’s temperinghardness falls quickly as temperature increase, the former’s tempering hardness fallsfast over450℃.Experiment plan to test the wear resistant of standard sample Cr12MoV steel andFe-Cr-B alloy though oil quenched at1050℃and tempered at250,350,400,450and550℃, by using MLD-10impact abrasion test machine. The test result shows that:when Cr content of Fe-Cr-B alloy is less than6%, the wear resistance is below thanCr12MoV steel; When Cr content of Fe-Cr-B alloy is greater than6%and less than15%,the wear resistance is flat or slightly higher than Cr12MoV steel. The wear resistanceproperty of Fe-Cr-B alloy declines as tempering temperature increase, but it picks up at450℃, then continues to decline. The main wear mechanism of Fe-Cr-B alloy isgouging and plastic deformation abrasive wear, brittle micro-peeling is not obvious.Therefore, Fe-Cr-B alloy has good wear resistance.更多还原