M7C3的形态分布对铁基复合层耐磨性能的影响

研究了在电磁搅拌的作用下,硬质相M7C3(主要是(Fe, Cr)7C3和Cr7C3)的数量和形态分布对堆焊层金属耐磨性的影响规律.对堆焊试件进行耐磨、硬度试验,并采用SEM,XRD对堆焊进行显微组织和成分分析.发现随着磁场参数的改变,硬质相M7C3由杂乱无章的分布逐渐转变为较规则的六方块状分布,堆焊层金属的耐磨性也随之增强;当磁场电流为3A,磁场频率为10Hz时,堆焊层金属的性能达到最佳状态,此时堆焊层中硬质相(M7C3)均成较规则的六方块状分布.结果表明,在适当的磁场参数作用下,硬质相(M7C3)成较规则的六方块状分布可以显著的提高堆焊层金属的耐磨性.     

Effect of different carbides on the wear resistance of Fe-based hardfacing alloys

Hardfacing plates are being used in raw material conveying system of an integrated steel plants to mitigate the wear of chutes and hoppers. Four Fe-based commercial hardfacing alloys were studied in this work. To prepare test samples, mild steel base plates was used. In hardfaced plates, mild steel backing provides the weldability, formability, and ductility whereas the hard weld deposit provides the required wear resistance. This investigation aims to correlate microstructural, tribological and hardness properties of hardfacing plate samples with varying chemical composition. Microstructural characterization involved the morphological study and elemental analysis of different types of carbides through EDS, hardness evaluation mainly involved measurement of bulk hardness and micro-hardness, whereas tribological studies involved pin-on-disc wear test. Higher hardness doesn't always mean higher wear resistance. Presence of alloying elements resists the material removal by abrasive action and increases the wear resistance.     

Influence of alloying elements on the structure and wear resistance of chilled cast iron

To work out the optimal chemical composition of wear-resistant cast iron with a pearlitic metallic matrix that is able to restore the relief of a rough surface, we investigated the properties of cast iron with different composition by the method of single factor experiment.Nizhnii Novgorod Branch of the Central Research Institute of Structural Materials Prometei. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 37–39, June, 1994.     

Correlation of microstructure with the wear resistance and fracture toughness of white cast iron alloys

The objective of this investigation was to set down (on the basis of the results obtained by the examination of white cast iron alloys with different contents of alloying elements) a correlation between chemical composition and microstructure, on one hand, and the properties relevant for this group of materials, i.e., wear resistance and fracture toughness, on the other. Experimental results indicate that the volume fraction of the eutectic carbide phase (M₃C or M₇C₃) have an important influence on the wear resistance of white iron alloys under low-stress abrasion conditions. Besides, the martensitic or martensite-austenitic matrix microstructure more adequately reinforced the eutectic carbides, minimizing cracking and removal during wear, than did the austenitic matrix. The secondary carbides which precipitate in the matrix regions of high chromium iron also influence the abrasion behaviour. The results of fracture toughness tests show that the dynamic fracture toughness in white irons is determined mainly by the properties of the matrix. The high chromium iron containing 1.19 wt% V in the as-cast condition, showed the greater fracture toughness when compared to other experimental alloys. The higher toughness was attributed to strengthening during fracture, since very fine secondary carbide particles were present mainly in an austenitic matrix.     

高硬度280Cr25Mo2W3耐磨铸铁合金碳化物的研究

通过显微组织观察、X射线衍射相结构分析、图像分析仪定量金相测试、扫描电镜观察和电子探针微区成分分析,研究了淬回火态280Cr25Mo2W3耐磨铸铁碳化物和基体成分,特别是M23C6二次碳化物的特性.结果表明,280Cr25Mo2W3铸铁M7C3相界附近基体的Cr、Mo、W成分低于初生枝晶晶体的成分.在初生枝晶中,中心区域的Cr、Mo、W成分较低,铸铁非平衡凝固和基体中析出M23C6是造成枝晶晶体成分偏析的原因.280Cr25Mo2W3铸铁共晶晶体上析出的二次碳化物M23C6数量少,颗粒小而且Cr、Mo、W等元素的含量较低,初生枝晶晶体上析出的M23C6数量多,颗粒大而且Cr、Mo、W等元素的含量较高.初生晶体上析出的M23C6为约lμm的方块状颗粒,M23C6颗粒有聚集长大的现象.M23C6中的W/Mo高于M7C3中的W/Mo,且二者均高于铸铁的W/Mo.在碳化物形成过程中W比Mo的作用大,特别是M23C6形成过程中W比Mo的促进作用更大.高硬度280Cr25Mo2W3耐磨铸铁的硬度达65HRC.     

白口铸铁磨面辊齿等离子弧重熔组织和耐磨性

利用等离子弧重熔技术对离心铸造白口铸铁磨面辊齿面进行强化处理,借助光学显微镜和洛氏硬度计观察测试重熔层的组织结构及硬度,并对重熔前后试样表面的耐磨性进行了对比试验.试验结果表明:辊齿经等离子弧重熔组织由亚共晶白口转变为共晶和过共晶的混合组织,拉齿破坏的离心铸造的流线的连续性得到恢复,辊齿齿顶的硬度由原来HRC58～60提高到了HRC64～65,耐磨性是重熔前的2～3倍.     

铌对高铬铸铁堆焊层耐磨性的影响

采用药芯焊丝堆焊的方式,以碳含量5%～6%和铬含量22%左右的高铬铸铁为基础,通过调整焊丝中铌的加入量,探讨了不加铌元素和添加6%的铌元素时,铌对耐磨性能的影响机理.铌在高铬铸铁中全部以碳化铌的形式存在,与碳化铬互不相溶.通过加入6%的铌,耐磨性能提高了16.9%.碳化铌的数量与铌的加入量有关.碳化铌形状为菱形.