热处理工艺对离心铸造高铬铸铁轧辊组织及硬度的影响

采用了光学显微镜、扫描电镜、X射线衍射仪、洛氏硬度计等仪器,研究了离心铸造高铬铸铁轧辊铸态及淬火与回火后的显微组织结构、碳化物和硬度等。结果表明:高铬铸铁轧铸态组织主要是由奥氏体+少量马氏体+(Cr,Fe)₇C₃碳化物组成,碳化物呈粗大板条状或块状,不同温度热处理后,得到回火马氏体+(Cr,Fe)₇C₃+Cr₇C₃碳化物的组织,组织中粗大板条状碳化物消失,得到细小块状或椭圆状碳化物。该高铬铸铁轧辊铸态硬度为56.0HRC左右,在950℃淬火及400℃回火处理后硬度增加到了约65.5HRC。     

Fe-Cr-Ti-C系药芯焊丝熔覆层中硬质相生长模式

将Fe-Cr-Ti-C系耐磨药芯焊丝采用钨极氩弧焊堆焊到低碳钢表面,分析熔覆层中的物相组成,研究熔覆层中硬质相的形态分布和生长机理,探究熔覆层的耐磨性及表面硬度等力学性能变化的原因. 结果表明,药芯堆焊焊丝中的合金元素的过渡系数很高,可原位合成(Fe,Cr)₇C₃和TiC硬质相,TiC优先依附外来界面行核、长大,共晶(Fe,Cr)₇C₃硬质相则依附于初生马氏体相和TiC形核生长,点状TiC硬质相(少数为条状和十字状)弥散分布于马氏体、残余奥氏体的基体中,与网状的(Fe,Cr)₇C₃耐磨框架组成复合硬质相,提高熔覆层的耐磨性.     

WxC增强镍基合金等离子堆焊层组织与空蚀性能

采用等离子堆焊技术在316L不锈钢表面原位合成W_xC增强镍基复合材料涂层,对涂层显微组织、相组成、硬质增强相的分布、显微硬度以及空蚀性能进行了分析.结果表明,Colmonoy 88合金等离子堆焊成形性良好,组织致密;堆焊层组织主要由γ-Ni固溶体,原位合成多角形、颗粒状W_xC及少量的Cr₇C₃,Fe₃W₃C,CrB₂相组成.堆焊过程中,熔池温度低于1 655 K时,原位生成WC和W₂C,温度高于1 655 K时,原位生成的WC发生了分解.镍基合金堆焊层平均硬度可达1 619 HV,为基材的8倍以上,在3.5% NaCl溶液中镍基复合材料抗空蚀性能为316L不锈钢基材的5倍.     

含Nb元素堆焊层金属中碳化物的析出行为

以堆焊连铸辊为研究对象,研制三种不同合金元素Nb加入量的药芯焊丝,采用金相显微镜和扫描电镜对其显微组织、碳化物形貌进行了观察. 采用X射线衍射仪对其相结构进行了测定. 采用Thermo-Calc软件对含铌堆焊层金属中碳化物的析出行为进行分析. 结果表明,堆焊层金属显微组织为铁素体、M₂₃C₆和MC. 随着Nb元素含量增加,其显微组织得到细化,NbC沿晶界析出. 热力学计算结果表明,析出碳化物主要为MC,M₂₃C₆. 随着Nb元素含量的增加,MC析出量增多,M₂₃C₆析出量减小. MC中主要是Nb元素,并溶解了一定量的Mo,V,Cr和Fe元素;M₂₃C₆中主要是Fe,Cr元素,即Nb元素含量变化主要影响MC型碳化物.     

等离子熔覆高铬铁基涂层的开裂行为与控制

以钛铁粉、铬粉、铁粉和碳的前驱体(蔗糖)等为原料通过前驱体碳化复合技术制备了复合粉末,并通过等离子熔覆技术在Q235钢表面制备了Fe-Cr-C和Fe-Cr-C-Ti涂层.采用XRD和SEM对涂层的相组成和显微组织结构进行了分析.结果表明,Fe-Cr-C涂层裂纹一般始于熔合区,沿初生碳化物(Cr,Fe)₇C₃晶界扩展成结晶裂纹,沿初生碳化物(Cr,Fe)₇C₃纤维方向扩展到涂层表面,形成垂直于涂层表面的垂直贯穿裂纹.少量裂纹起源于气孔或涂层边缘尖锐处.Fe-Cr-C涂层中添加Ti元素,可以合成大量TiC颗粒,形成奥氏体组织,减少或消除(Cr,Fe)₇C₃初生碳化物,改善(Cr,Fe)₇C₃共晶组织结构,有效提高了涂层韧性,抑制了涂层裂纹的产生.     

Fe-C-Cr-V高铬堆焊合金的M7C3型碳化物及耐磨性

采用药芯焊丝埋弧堆焊方法制备含有0.9%~3.0%C,15%~20%Cr,2.0%~3.0%V的高铬合金.借助光学显微镜、扫描电镜和X射线衍射等手段,研究其显微组织及碳化物分布形貌.结果表明,其显微组织由马氏体+铁素体+奥氏体+初生M7C3+(Fe,Cr)3C+TiC等相组成.通过优化药芯焊丝组份及调整堆焊速度,获得了沿堆焊表面垂直方向定向分布的初生M7C3型碳化物,电子能谱分析显示该碳化物为(Fe,Cr,V)7C3.此外,考察了碳含量对高铬堆焊合金硬度及耐磨粒磨损性能的影响.表明其耐磨性优良,其中15~25μm M7C3型初生碳化物颗粒有效阻碍磨粒的显微切削运动,显著改善了耐磨性.     

碳化硼对粉/丝复合堆焊高硼铁基合金组织结构的影响

为了探讨合金元素B,C对高硼铁基堆焊合金组织结构、裂纹敏感性的影响,采用粉/丝复合堆焊技术配合不同B₄C含量合金粉体制备高硼铁基堆焊合金,通过显微组织结构、微区成分、显微硬度及宏观硬度试验检测,分析不同B,C元素含量及配比的堆焊合金组织与性能. 结果表明,高硼铁基堆焊合金由α-Fe,Fe₂B,Fe₃(C,B)相组成,随着B₄C的添加,初晶岛状α-Fe消失,菱形初晶Fe₂B、粒状Fe₃(C,B)析出,鱼骨状、条状共晶状组织α-Fe+Fe₂B体积分数趋于减小并消失,菊花状α-Fe+Fe₂B+Fe₃(C,B)包晶组织成为堆焊合金的主体. 高硼铁基合金中硼、碳的含量及配比是影响堆焊合金组织结构、裂纹敏感性的原因之一,约30%合金粉体(含35%硼铁粉、5%B₄C)配合约70%H08Mn2Si焊丝获得的堆焊层,可有效抑制堆焊裂纹的出现,并可获得稳定的高硬度值66 HRC.     

自保护药芯焊丝明弧堆焊Fe-Cr-C-B-W合金的组织及性能

采用自保护药芯焊丝明弧堆焊技术制备五组不同钨含量的Fe-Cr-C-B-W合金. 借助金相显微镜、扫描电子显微镜、X射线衍射仪、洛氏硬度计和磨损试验机分析堆焊合金的组织及性能. 结果表明,合金的显微组织由马氏体、残余奥氏体、M₇(C,B)₃,M₃(C,B),Fe₃W₃C和WC组成. 大部分钨元素被迁移到晶界生成了比WC稳定性更好的Fe₃W₃C缺碳复合相,堆焊层中没有典型的初生WC硬质相颗粒生成. 随着钨添加量的增多,共晶硬质相M₇(C,B)₃,M₃(C,B)和Fe₃W₃C随之增多,间距减小,呈连续网状均匀分布. 当钨的添加量为12%时,堆焊层的耐磨性达到最佳.     

Cr26型高铬铸铁水泥球磨机耐磨衬板的开发

开发了一种具有高耐磨性的Cr26型高铬铸铁水泥球磨机衬板材料,采用正交试验的方法获得试验铸铁最佳热处理工艺,并对其组织及性能进行分析。结果表明,试验材料最佳热处理工艺为1 050℃×3 h油冷+300℃×2 h空冷,显微组织为回火马氏体+(Fe,Cr)₇C₃共晶碳化物+二次碳化物+残余奥氏体,硬度HRC58,冲击韧度3 J/cm²。在最佳热处理状态下,该试验材料具有优异的耐磨性,为12.739 g^-1,但其冲击韧度较低。经过最佳热处理工艺后该试验材料耐磨性能优异,可作为高耐磨性的水泥球磨机衬板材料。     

TiN对Fe-Cr-C耐磨堆焊合金组织及耐磨性影响

通过药芯焊丝的方式制备Fe-Cr-C-Ti-N和Fe-Cr-C堆焊层，讨论堆焊层中TiN对堆焊层耐磨性能和显微组织的影响. 利用洛氏硬度计检测堆焊层的宏观硬度，通过湿砂轮磨损试验机对堆焊层进行磨料磨损试验，利用X射线衍射仪(XRD)、扫描电镜(SEM)、能谱分析仪(EDS)、透射电子显微镜(TEM)等设备进行检测分析. 结果表明，含有TiN的堆焊层中，初生M₇C₃明显比不含TiN的组织细小，并且堆焊层硬度和耐磨性也相应提高. 通过热力学计算得出，熔池冷却过程中TiN先于M₇C₃析出. 由动力学计算可知TiN/M₇C₃的二维错配度为8.43%，TiN可做为初生M₇C₃的异质形核质点，使M₇C₃晶粒细化.     

Microstructure and abrasive wear properties of Fe-Cr-C hardfacing alloy cladding manufactured by Gas Tungsten Arc Welding (GTAW)

A series of Fe-Cr-C hardfacing alloys is deposited by gas tungsten arc welding and subjected to abrasive wear testing. Pure Fe with various amounts of CrC (Cr:C=4:1) powders are mixed as the fillers and used to deposit hardfacing alloys on low carbon steel. Depending on the various CrC additions to the alloy fillers, the claddings mainly contain hypoeutectic, near eutectic, or hypereutectic microstructures of austenite γ-Fe phase and (Cr,Fe)₇C₃ carbides on hardfacing alloys, respectively. When 30% CrC is added to the filler, the finest microstructure is achieved, which corresponds to the γ-Fe+(Cr,Fe)₇C₃ eutectic structure. With the addition of 35% and 40% CrC to the fillers, the results show that the cladding consists of the massive primary (Cr,Fe)₇C₃ as the reinforcing phase and interdendritic γ-Fe+(Cr,Fe)₇C₃ eutectics as the matrix. The (Cr,Fe)₇C₃ carbide-reinforced claddings have high hardness and excellent wear resistance under abrasive wear test conditions. Concerning the abrasive wear feature observable on the worn surface, the formation and fraction of massive primary (Cr,Fe)₇C₃ carbides predominates the wear resistance of hardfacing alloys. Abrasive particles result in continuous plastic grooves when the cladding has primary γ-Fe phase in a hypoeutectic structure.     

Microstructure and properties of Fe–Cr–C hardfacing alloys reinforced with TiC–TiB2

Abstract

Different amounts of TiB₂ powder were added to flux cores of wear resistant hardfacing flux cored wires for the preparation of new flux cored wires. Fe–Cr–C hardfacing alloys reinforced with TiB₂ were produced by arc hardfacing. The microstructure, hardness and wear resistance behaviour of the hardfacing alloys were investigated using an optical micrograph, scanning electron micrograph (SEM), X-ray diffractometer, macrohardness tester, microhardness tester and abrasive wear tester. The results showed that, among the hardfacing alloys, a new hard phase, i.e. TiC–TiB₂ composite compound particles, was formed and dispersed in the primary carbides and matrix structures. The TiC–TiB₂ reinforced Fe–Cr–C hardfacing alloys imparted greater hardness and better wear resistance. The presence of TiC–TiB₂ hard phase particles is the main reason for the improvement in hardness and wear resistance of Fe–Cr–C hardfacing alloys.     

Microstructural evolution with various Ti contents in Fe-based hardfacing alloys using a GTAW technique

The aim of this study is to discuss the effect of microstructural development with different Ti contents in Fe-based hardfacing alloys. A series of Fe-Cr-C-Si-Mn-xTi alloy fillers was deposited on SS400 low carbon steel substrate using oscillating gas tungsten arc welding. The microstructure in the Fe-based hardfacing alloy without Ti content addition included: the primary γ, eutectic γ+(Fe,Cr)₃C, eutectic γ+(Fe,Cr)₂C and martensite. With increasing Ti contents, the microstructures showed the primary TiC carbide, γ phase and eutectic γ+(Fe,Cr,Ti)₃C. The amount and size of TiC carbide in the hardfacing layers increased as the Ti content increased. However, the eutectic γ+(Fe,Cr,Ti)₃C content decreased as the Ti content increased. According to the results of the hardness test, the lowest hardness value (HRC 54.93) was found with 0% wt% Ti and the highest hardness (HRC 60.29) was observed with 4.87 wt% Ti.     

Fe-Cr-V耐磨堆焊合金

制备了用于埋弧焊药芯焊丝的Fe-Cr-V堆焊合金,其成份(质量分数,%)为c0.9～1.5,Cr 13～15,V 1.0-2.0.借助光学显微镜、扫描电镜和X射线衍射等手段,研究了其显微组织,并考察V和B4C含量对该堆焊合金性能的影响.Fe-Cr-V堆焊合金的显微组织由铁素体 马氏体 (Cr,Fe)23C6等碳化物组成.电子能谱微区分析显示Cr,V元素晶界含量显著高于晶内,随WC加入量提高,晶界与晶内含量差距增大.由于沿晶界析出碳化钒,这使(Cr,Fe)23C6等晶界碳化物呈条状或断续网状分布,起到耐磨骨架作用,避免了网状形态的强烈脆性.结果表明,其磨粒磨损性能显著优于实心焊丝H25Cr3Mo2MnV堆焊合金.     

纳米 Y2 O3 对过共晶 Fe-Cr-C 堆焊合金表面微观组织与耐磨性的影响

目的研制一种新型添加纳米Y2O3的过共晶Fe-Cr-C堆焊合金,改善堆焊合金粗大的初生M7C3碳化物,提高堆焊合金的耐磨性。方法采用明弧堆焊的方法制作堆焊合金,用金相电子显微镜对其表面微观组织进行观察,用洛氏硬度计对其表面硬度进行测量,用砂带摩擦磨损试验机对其表面耐磨性进行评价,用扫描电子显微镜对其磨损形貌进行观察。最后,利用错配度理论对M7C3的细化机理进行分析。结果过共晶Fe-Cr-C堆焊合金由初生M7C3和共晶组织(共晶M7C3、奥氏体及部分马氏体)组成。未添加Y2O3的堆焊合金初生M7C3比较粗大,其平均尺寸在22μm,硬度为55HRC,磨损量为0.85mg/mm2。经纳米Y2O3改性之后,堆焊合金的初生M7C3尺寸变小,其平均尺寸为16μm,硬度为57HRC,磨损量减少为0.59 mg/mm2,Y2O3的(001)面与正交M7C3的(100)面之间的二维错配度为8.59%。结论 Y2O3可以成为M7C3的非均质形核核心,从而细化了过共晶Fe-Cr-C堆焊合金的初生M7C3碳化物,提高了过共晶Fe-Cr-C堆焊合金表面耐磨性。     

Influence of cooling rate and composition on orientation of primary carbides of Fe–Cr–C hardfacing alloys

Abstract

Four Fe–Cr–C hardfacing alloys with carbon contents of 3˙34–6˙5% were studied. The orientation of primary carbides in the microstructures of hardfacing layers produced by arc surfacing was investigated under controlled cooling conditions. Carbon content and cooling conditions were found to play an important role in determining overlayer microstructures. Increasing carbon content or decreasing Cr/C ratio increased the tendency for primary carbides to be oriented perpendicular to the surface of the overlayers, and the carbides in the microstructure became more compact. Under water cooling conditions, the primary carbides were preferentially oriented perpendicular to the surface, which would be expected to improve wear resistance. At lower cooling rates, primary carbides were oriented randomly.     

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.     

硼对等离子熔覆高硼铁基合金组织和性能的影响

采用等离子弧熔覆技术在20g钢表面堆焊Fe-Cr-B-C系的铁基复合材料,利用X射线衍射（XRD）,光学显微镜（OM）,扫描电镜（SEM）,洛氏硬度计及湿砂磨损试验机等试验设备进行检测、试验,研究不同硼加入量对熔覆层显微组织与性能的影响规律.结果表明,熔覆层显微组织由过饱和α-Fe枝晶固溶体、枝晶间硼化物共晶组织以及碳化物等组成;熔覆层中硬质相主要有Cr2B,CrB2,Fe2B,Cr7C3,B4C等;随着硼含量的增加,硼化物明显增多,当硼添加量为5%时熔覆层的硬度及耐磨性达到最佳,其硬度值为66.1 HRC,磨损量仅为0.383 g;继续增加硼的添加量,熔覆层的耐磨性能降低.     

B4C对高碳铬铁自保护药芯焊丝力学性能的影响

通过改变高碳铬铁中熔覆金属B4C的含量,分别考察了B4C对堆焊熔敷金属金相组织、硬度和不同载荷下耐磨性的影响,并对堆焊熔敷金属磨损形貌进行了分析.结果表明,随B4C含量的增加,初生碳化物的生长方向性越来越明显,成定向生长趋势,并且熔敷金属的宏观硬度逐渐增大,但B元素含量超过0.5%时,硬度变化趋缓;不同载荷磨损条件下,B4C强化的熔敷金属表现出耐磨性不同,堆焊熔敷金属耐磨面碳化物断裂或剥落少时,表现出良好的耐磨性,当碳化物大量断裂或剥落时,耐磨性变差.     

元素添加量对水等离子弧堆焊铁基合金层的影响

采用正交试验方法设计了几种铁基合金系堆焊粉末,利用水等离子火焰机在Q345钢板上进行堆焊,分析了Cr,Mo,Si,C添加量对堆焊层硬度、显微组织及磨损性能的影响。结果表明:堆焊层中含有大量的M7C3初生碳化物及共晶组织,最高硬度可达到56.8HRC,耐磨性较好,Cr和C对堆焊金属的耐磨性影响最大。试验表明,采用水等离子火焰机可以较好地进行粉末堆焊。