铌铬白口铸铁中碳化物的形态及其对性能的影响

介绍了铌铬白口铸铁中的碳化物形态及分布规律。认为铌在白口铸铁中以NbC形式与奥氏体形成共晶体,在共晶体内,NbC呈条形放射状;在铌铸铁中加入钛,TiC先于NbC析出,随后NbC围绕TiC结晶,最终形成团块状,使这种白口铸铁具有更高的抗磨性能和更高的韧性。     

含铌铸铁冶金学基础

论述了铌对铸铁显微组织和性能的影响,铌在铸铁中以NbC形式与奥氏体形成共晶体。在共晶体中NbC呈条形放射状。在铌铸铁中加入钛,形成TiC先于NbC析出,随后NbC围绕TiC结晶,最终形成团块状。     

铌微合金化高强度灰铁气缸盖的开发

研究了微量铌元素对灰铁组织和力学性能的影响,成功开发出一种铌微合金化高强度灰铁气缸盖。结果表明,微量铌元素的加入使石墨、共晶团、碳化物及磷共晶细化,珠光体片间距减小,基体得到强化,灰铁试样的抗拉强度、韧性、疲劳性能和热疲劳性能都得到提高。当加入的W（Nb）=0．20％时,材料的综合力学性能较好。铌在灰铁中以两种形式存在：绝大多数在共晶团边界处形成独立的富铌相,少数固溶于珠光体基体中。采用W（Nb）为0．20％的微合金化灰铁浇注的气缸盖,本体强度均在300MPa以上,达到HT300牌号的要求。气缸盖通过了1000h冷热冲击耐久性和2000h“11工况”耐久性台架试验考核,满足使用要求。     

Sr,B添加对Al-15.5%Si合金中共晶团尺寸的影响

考察了Sr,B及Sr＋B联合作用对Al-15．5％Si（质量分数）合金中共晶团尺寸大小的影响．实验结果表明,随合金中Sr量增加,共晶团尺寸呈减少的趋势,冷却速度对共晶团的影响也很显著;在Sr变质的合金中加入B,共晶团尺寸先显著下降,随B量增加降低幅度趋于平缓;在未变质的Al-15.5％Si合金中单独加B,共晶硅由粗大的片状变为细长的层片状,层片间距明显降低．分析认为,合金中加入Sr,导致共晶过冷度增大,因而共晶团形核驱动力增大促使共晶团细化;合金中加入B,增加了共晶团有效形核基底的数量促使共晶团显著细化．     

微量铌对灰铸铁组织和性能的影响

研究了加入微量铌对灰铸铁组织和性能的影响。试验表明:铌在灰铸铁中能细化共晶团—改变石墨形态和提高铸铁的常温和高温机械性能及改善胁磨性.     

钨合金铸铁共晶碳化物团球化研究

研究了Ce、K、Na复合变质处理对钨白口铸铁组织和性能的影响，提出了评价碳化物变质效果的圆度概念。变质处理后，钨合金白口铸铁的共晶碳化物形态发生了显著变化，在常规热处理条件下，共晶碳化物变成了团球状。由于共晶碳化物形态的改善，钨合金白口铸铁的力学性能（尤其是冲击韧度和抗冲击磨损性能显著提高。对共晶碳化物团球化机理进行了深入分析，并讨论了共晶碳化物团球化对力学性能和耐磨性能的影响。变质钨合金白口铸铁轧辊使用寿命比高铬铸铁轧辊提高20％以上，生产成本降低30％以上，推广应用变质钨合金白口铸铁具有较好的经济效益．     

钨合金铸铁共晶碳化物团球化研究

研究了Ce、K、Na复合变质处理对钨白口铸铁组织和性能的影响,提出了评价碳化物变质效果的圆度概念。变质处理后,钨合金白口铸铁的共晶碳化物形态发生了显著变化,在常规热处理条件下,共晶碳化物变成了团球状。由于共晶碳化物形态的改善,钨合金白口铸铁的力学性能(尤其是冲击韧度和抗冲击磨损性能显著提高。对共晶碳化物团球化机理进行了深入分析,并讨论了共晶碳化物团球化对力学性能和耐磨性能的影响。变质钨合金白口铸铁轧辊使用寿命比高铬铸铁轧辊提高20%以上,生产成本降低30%以上,推广应用变质钨合金白口铸铁具有较好的经济效益。     

NbC增强Fe-Cr-C耐磨堆焊合金组织与磨粒磨损性能

以H08A为焊芯,在Fe-Cr-C耐磨合金焊条药皮中加入NbC,对堆焊层组织及NbC对堆焊层硬度和耐磨性的影响进行了研究.结果表明,NbC增强Fe-Cr-C耐磨合金的宏观硬度和耐磨性都高于Fe-Cr-C合金,宏观硬度达到61.6 HRC,比Fe-Cr-C耐磨合金提高9.6%;相对耐磨性提高60%.NbC增强Fe-Cr-C耐磨合金中NbC硬质相断面呈不规则形状,分布于M7C3之间,或镶嵌在M7C3中,以菱形或多边形居多,NbC分布不均匀,有局部聚集的区域.与Fe-Cr-C耐磨合金的共晶碳化物比较,Fe-Cr-C-NbC合金的共晶碳化物要粗大,共晶碳化物的间距也较大.     

铌和热处理对高铬铸铁组织性能的影响

在无钼高铬铸铁中加入适量铌和锰,研究了热处理工艺对其组织和性能的影响.结果表明;加铌并配合高温淬火-亚临界回火工艺,可改善共晶碳化物的形态和分布,并产生明显的二次硬化.试验合金的宏观硬度与Cr15Mo1Cu1高铬铸铁相当,而抗磨性优于后者.     

Nb强化铸铁机理的基础研究

介绍了Nb在铸铁中的应用现状,对富铌相在铸铁中的存在形式和形成条件进行了热力学分析。通过NbC和铸铁组织中的γ-Fe和石墨的晶格点阵的二维错配度计算,证实了NbC可以成为石墨异质晶核的衬底。提出了进一步研究Nb元素对铸铁作用机理的方向。     

Enhancement of wear resistance and impact toughness of as cast hypoeutectic high chromium cast iron using niobium

The effect of niobium additions on the as-cast microstructure of a hypoeutectic high-Cr cast iron containing 2.2 wt.% C and 16.5 wt.% Cr was investigated. With increasing niobium content, the eutectic M₇C₃ carbides were refined and became less elongated as well as its volume fraction was decreased gradually. The first precipitated NbC particles could be act as heterogeneous substrate of proeutectic austenite and a barrier to M₇C₃ grain growth. The morphology of NbC carbides changed with increasing niobium content. Such NbC particles were increased with increasing Nb content and subsequently contributed to increased hardness. Optimum toughness was obtained for the irons alloyed with 2.14% Nb. The effects of applied load and Nb-additions on wear resistance of high chromium cast iron have been studied. The results showed that wear resistance increases with increasing Nb addition. Furthermore, the effectiveness of the NbC particles on the weight loss was more evident at higher loads.     

Nb在铸铁中的物理冶金学作用原理

介绍了Nb在铁基合金中的存在形式,根据NbC和NbN在不同铁基合金中的溶度积公式,分析了Nb在铸铁中的存在形式。在此基础上,分析了Nb在铸铁中的作用机理。固溶Nb具有非常重要的调节共析相变及强化铁素体基体的作用,凝固过程析出的Nb（C,N）可显著提高耐磨性,在奥氏体温度区间晶界析出的Nb（C,N）能有效阻止晶粒长大,合适的成分设计和工艺措施可充分发挥Nb的作用效果。     

Niobium alloying effect in high carbon equivalent grey cast iron

The effect of niobium on the formation of NbC phase and solidification structure in high carbon equivalent grey cast iron was investigated.The experimental results indicated that an increase in the niobium content is favorable to refining the graphite and eutectic cell;and the pearlite lamellar spacing is reduced.Based on the thermodynamic calculation the formation of NbC is prior to the eutectic reaction.The reduction in the pearlite lamellar spacing is mainly attributed to the decrease of eutectic tempera...     

Microstructure and wear resistance of highchromium cast iron containing niobium

In the paper, the effect of niobium addition on the microstructure, mechanical properties and wear resistance of high chromium cast iron has been studied. The results show that the microstructure of the heattreated alloys is composed of M7C3 and M23C6 types primary carbide, eutectic carbide, secondary carbide and a matrix of martensite and retained austenite. NbC particles appear both inside and on the edge of the primary carbides. The hardness of the studied alloys maintains around 66 HRC, not significantly affected by the Nb content within the selected range of 0.48%-0.74%. The impact toughness of the alloys increases with increasing niobium content. The wear resistance of the specimens presents little variation in spite of the increase of Nb content under a light load of 40 N. However, when heavier loads of 70 and 100 N are applied, the wear resistance increases with increasing Nb content.     

Nb对高CE灰铸铁耐磨性能的影响

研究了Nb对高CE灰铸铁耐磨性能的影响,结果表明：（1）Nb可以提高灰铸铁的耐磨性,加入0.25%的Nb时,铸铁的相对耐磨性可提高55%;（2）Nb在基体组织中的固溶强化作用提高了基体的显微硬度,当w（Nb）量为0.46%时,基体显微硬度提高40%;（3）灰铸铁耐磨性能的提高应该归因于基体中的富Nb相,因为富Nb相在基体中的分布及形态对提高铸铁的耐磨性起着明显的作用。     

Nb对灰铸铁热疲劳性能的影响

采用Uddeholm热疲劳方法测定了Nb对灰铸铁热疲劳性能的影响,试验结果表明：（1）Nb的加入能够提高灰铸铁的抗热疲劳性能,随着w（Nb）的增加,试样最大裂纹深度和宽度都逐渐减小;（2）由于Nb细化石墨使裂纹源减少和裂纹扩展途径变细,Nb元素能够改善材料表面经热疲劳处理后恶化的性能。     

Microstructure and wear mechanism change by Nb added in slag free self-shielded flux cored wire

Abstract

The iron based hardfacing alloys were produced using slag free self-shielded flux cored wires with varying niobium contents. The results show that NbC acted as the nucleus of primary M₇(C, B)₃ (M?=?Cr, Fe mainly) carbides and decreased the amount of M₇(C,B)₃ carbides when niobium was added into the alloys. When 18?wt-%Fe–Nb (60?wt-%Nb) was added, the microstructure of hardfacing alloy transformed from hypereutectic structure to a eutectic one due to the formation of NbC, which consumed a mass of carbon. The microstructure changed into a hypoeutectic structure when the Fe–Nb content was up to 24?wt-%. With the increase in Fe–Nb content, the main abrasive wear mechanism changed from microcracking to microcutting and microploughing due to the formation of NbC and the reduction of primary M₇(C, B)₃ carbides. The wear loss of the alloy with 18?wt-%Fe–Nb addition was the smallest among all the alloys.     

等离子熔覆超细碳化铌颗粒增强铁基复合材料中碳化物尺寸的控制

采用两种方法控制Fe-Cr-B-C-Nb堆焊合金中原位合成的碳化铌尺寸.通过调整熔覆的合金体系,设计出了新型铁基耐磨堆焊合金.对铌含量分别为2.2%,3.2%,3.9%,5.0%的合金,采用等离子熔覆原位合成方法,制备出了具有亚微米尺度碳化铌弥散分布的耐磨合金,并实现了对碳化铌尺度的控制.结果表明,提高铌含量会使合金中原位合成碳化铌尺寸增加,且碳化物分布有聚集的倾向.控制冷却条件对控制原位合成的碳化铌尺寸有重要的影响,采用强迫水冷却方法可减小原位合成碳化铌尺寸,当改变冷却条件降低冷却速率时,合金中的碳化铌尺寸增大.