高铬铸铁耐磨堆焊层组织结构和硬度分析

应用两种高铬铸铁焊条和一种高铬铸铁药芯焊丝对低碳钢进行堆焊,通过光学显微镜、扫描电镜和洛氏硬度计等设备仪器对三种高铬铸铁耐磨堆焊层的组织结构和硬度进行观察、测试。分析后表明,三种堆焊层的组织结构都随堆焊层厚度的变化而呈现有规律的变化;三种堆焊层在厚度方向上随位置不同其硬度也不同,越接近堆焊层表层则硬度越高。总体结果显示,药芯焊丝堆焊层的组织结构和硬度分布较为均衡。     

添加Mo对高铬铸铁组织及亚临界处理硬化作用的影响研究

为提升高铬铸铁的综合性能,以无Mo高铬铸铁和含1.0％(质量分数)Mo高铬铸铁为研究对象,对比研究了添加Mo元素对铸态高铬铸铁组织结构以及550℃亚临界处理对其组织及硬度的影响.研究表明:2种铸态高铬铸铁的主要组成相均为奥氏体、马氏体及(Cr,Fe)7C3,但含Mo高铬铸铁中奥氏体含量明显增多.铸态高铬铸铁均以亚共晶方式结晶,其组织为初生树枝晶固溶体及其间的共晶组织组成,但含Mo高铬铸铁的树枝晶组织发生了明显细化.2种高铬铸铁经过550 ℃下不同保温时间的亚临界处理后均出现了硬化现象,但含Mo高铬铸铁的硬度峰值(50 HRC)比铸态硬度提高了31.6％,无Mo高铬铸铁的硬度峰值(48 HRC)比铸态硬度提高了14.2％;含Mo高铬铸铁的硬度峰值出现时间(15 h)长于无Mo高铬铸铁(5 h).Mo元素细化了高铬铸铁的枝晶组织,并提供了其亚临界处理后的硬化效果.     

高铬离心复合铸铁轧辊辊身工作层剥落分析

高铬离心复合铸铁轧辊辊身工作层在热处理后发生大面积剥落,采用金相检验和化学分析等测试手段对 辊剥落进行了分析,结果表明,化学成分的不均匀分布,造成轧辊辊身工作层组织不连续、碳化物形态各异使螺身工作层硬度不均匀,产生大面积剥落,最终导致轧辊报废。     

316L-Q345R不锈钢复合板性能评价

从微观组织和显微硬度两方面对真空热轧316L-Q345R不锈钢复合板试样性能进行评价。采用电子显微和能谱分析技术,对试样进行微观组织特征观察和成分含量测定,研究相结构及成分变化规律。通过硬度测试仪对复合板界面附近硬度进行测量,研究微观组织与硬度关系。结果表明:热轧后复合板Q345R侧显微组织以铁素体和珠光体为主,316L侧显微组织为单一奥氏体,一部分晶粒呈孪晶状态,Q345R低合金钢和316L不锈钢经过热轧可良好复合,复合界面平直;界面两侧元素存在扩散现象,不锈钢中Cr,Ni元素向低合金钢侧扩散,在界面形成富Cr,Ni薄层,低合金钢中C向不锈钢侧产生少量迁移;在复合界面处的硬度值较大,低合金钢侧远离界面位置复合板硬度与Q345R本身硬度值接近,而从界面到不锈钢侧硬度呈现先下降后上升至稳定的趋势。     

TaC增强铁基梯度复合材料的原位生成及其磨粒磨损特性

以高纯钽板为原料,采用原位反应法在HT300表面制备了碳化钽增强表面梯度复合材料。用扫描电子显微镜、X射线衍射仪、显微硬度计和磨粒磨损试验机对复合层的微观形貌、物相组成、显微硬度以及磨粒磨损性能进行了表征。结果表明:所得复合层的总厚度约为475μm。最表层为碳化钽致密陶瓷层,厚度约为170μm,其颗粒尺寸小于1μm,体积分数近似95%,显微硬度最高值达2328HV0.1;次表层为碳化钽颗粒分散层,其颗粒尺寸为0.5~1.5μm,体积分数从90%逐渐减小至基体,显微硬度由915HV0.1降低至410HV0.1;复合层与基体之间呈现良好的冶金结合。铁基表面碳化钽陶瓷增强梯度复合材料的耐磨性比灰口铸铁基体有大幅度提高;复合层的磨损是局部塑性变形、显微切削和增强颗粒的部分破碎等因素综合作用的结果。     

稀土变质处理对耐磨高铬铸铁组织性能的影响

本文采用稀土变质荆对高铬铸铁进行变质处理,通过OM和SEM测试观察高铬铸铁变质处理前后及热处理前后的形貌及微观组织,并通过硬度、冲击韧性及磨损量测试研究变质和热处理对其力学性能的影响。结果表明：高铬铸铁在经过稀土变质处理后组织细化,网状碳化物破碎成孤立块状,硬度、冲击韧性及耐磨性提高;经过950℃-1000℃正火处理后,碳化物进一步破碎,在奥氏体基体上析出弥散的二次碳化物,进一步提高了高铬铸铁的硬度、韧性和耐磨性能。     

压力条件下固-液复合法制备铜/锌复合材料的研究

采用压力条件下固-液复合法,在不同的锌液浇注温度下制备了铜/锌复合材料,并对其界面结合质量、组织成分和硬度等进行分析研究。结果表明:在铜板预热温度440℃,锌液浇注温度420℃时,可以获得厚度约为8μm、冶金结合良好的复合界面,此时界面层抗拉强度大于40.86MPa,超过铸态锌基体的抗拉强度;随着锌液浇注温度的升高,界面层厚度增加,抗拉强度降低,界面层生成的金属间化合物(CuZn)增多;界面层硬度显著高于基体硬度。     

无压渗透法制备铸造表面复合材料

提出用无压渗透法制备铸造表面复合材料的新方法。通过预先制备带有孔隙的硼铁合金 预制块, 用普通浇注的方法, 获得以灰铸铁为基的铸造表面复合材料。复合层从化合物层到亚共晶 层的厚度达8 mm , 其组织和硬度由表层向基体呈梯度分布, 表面化合物及过共晶层的耐磨性优于 Cr12 型高铬铸铁。      

高铬铸铁耐磨材料在泥沙磨损条件下耐磨性影响因素分析

分析了碳化物形态与分布、基体组织和稀土变质处理对高铬铸铁耐磨材料在泥沙磨损条件下的耐磨性影响。结果表明：碳化物的形态和分布对高铬铸铁的耐磨性有直接影响,块状或短杆状且分布均匀的碳化物对提高材料的耐磨性有利,网状或长针状碳化物对耐磨性不利;在泥沙磨损试验条件下,提高高铬铸铁中基体组织的显微硬度和基体组织与碳化物的结合强度有利于提高高铬铸铁材料的耐磨性;稀土元素的加入,使高铬铸铁的晶粒细化,碳化物颗粒变得细小,分布更为均匀,有利于提高高铬铸铁在泥沙磨损条件下的耐磨性。     

高铬合金铸铁化学成分的优化分析

通过分析对合金铸铁化学成分的添加及量的控制,改善高铬铸铁共晶碳化物的数量、形态和分布;通过稀土、钒、钛的微量加入及复合变质处理使高铬铸铁组织细化,并进一步改善碳化物形态,获得硬度、耐磨性和韧性的良好配合。     

Reinforcement of Hadfield steel matrix by oriented high‐chromium cast iron bars

To attain a wear‐resistant material compatible with high hardness and high toughness, Hadfield steel matrix was reinforced by oriented high chromium cast iron bars, through inserting high chromium alloys flux‐cored welding wires into Hadfield steel melt at 1500 ± 10 °C. The obtained composites were investigated by XRD, SEM, micro‐hardness, three‐body abrasion wear and impact toughness testers. The results show that the alloy powders inside the flux‐cored welding wires can be melted by the heat capacity of Hadfield steel melt and in situ solidified into high chromium cast iron bar reinforcements tightly embedded in the matrix. The micro‐hardness of reinforcements of the water‐quenched composite is about four times higher than that of the matrix. The impact toughness of the water‐quenched composite is higher than that of the as‐cast composite and lower than that of Hadfield steel, and its fracture mechanism is very complicated and refers to brittle and ductile mixture fracture mode. The excellent impact toughness and better wear resistance of the water‐quenched composite are attributed to combine fully the advantages and avoid the drawbacks of both Hadfield steel and high chromium cast iron. Additionally, in industrial application, the pulverizer plate produced by this composite, has also better wear resistance compared to the reference Hadfield steel pulverizer plate.     

Influence of carbon diffusion on microstructure and wear behaviour of duplex stainless steel surface layers on lamellar grey cast iron

Surface welding with duplex stainless steel was performed to enhance the wear and corrosion properties of grey cast iron, which is used as material for applications as pump components in maritime and chemical environments. The method used for surface welding and the corresponding process parameters determine the chemical composition and microstructure, which both determine the corrosion and wear properties of the surface layer. High heat input leads to high chemical dilution and thus, reduced corrosion resistance. Slow cooling rates, which are recommended for welding of grey cast iron components, facilitate the formation of carbides in the fusion zone of the chromium‐rich duplex stainless steel surface layer. On the one hand, carbides lead to increased hardness and thus, improved wear resistance of the surface layers. On the other hand, carbides and high chemical dilution rates reduce the corrosion resistance and therefore should be avoided. Under high cooling rates, the risk of cracking in the heat affected zone of the grey cast iron increases due to martensitic phase transformations. The paper describes the correlation of process parameters, microstructure and chemical composition with a focus on carbon diffusion and carbide formation, ever considering the effect on the wear behaviour in an oscillation tribometer and under erosion‐corrosion conditions.     

粉末烧结法和铸造法制备ZrO2增韧Al2O3陶瓷颗粒增强高铬铸铁基复合材料及其耐磨性能

将粒径为1~2 mm的ZrO₂增韧Al₂O₃陶瓷颗粒(ZTA_p)、高铬合金粉末和黏结剂混合真空烧结制备蜂窝状预制体,再浇注高铬铸铁液制备出ZTA_p增强高铬铸铁基复合材料。采用SEM、EDS、XRD分析复合材料的界面微观结构和物相组成,通过三体磨损试验评价复合材料的耐磨性能。结果表明,烧结高铬铸铁基体在铸造过程中发生重熔,与铸造高铬铸铁基体呈冶金结合,ZTA_p与金属基体界面结合致密,无裂纹、气孔等缺陷。复合材料三体耐磨性能达到高铬铸铁的3倍以上。将该复合材料应用于制备磨辊件,经过5 000 h服役,柱状区和复合区在磨辊半径方向上的磨损量分别为8.2 mm、5.9 mm,预计寿命可达到高铬铸铁磨辊的2倍以上。      

高铬白口铁－钢双金属焊铸初探

本文初步探讨了在高铬白口铁镶件表面上镀上一定厚度的铜，然后浇注铸钢的焊铸法生产双金属，该法工艺简单，双金属结合牢固，具有实际使用价值。     

高铬白口铸铁干滑动摩擦磨损特性的研究

研究了两种碳化物 ((Fe,Cr) 2 3 C6型碳化物和 (Fe,Cr) 7C3 型碳化物 )和 3种基体组织 (共析组织、马氏体组织和奥氏体组织 )的高铬白口铸铁与淬火 4 0Cr钢对磨时的干滑动摩擦磨损特性。试验结果表明 ,与(Fe,Cr) 2 3 C6型碳化物相比 ,(Fe,Cr) 7C3 型碳化物有利于提高高铬白口铸铁的耐磨性 ,降低其摩擦系数 ;在高接触应力情况下 ,与马氏体和奥氏体基体的合金相比 ,共析组织基体的合金具有更大的摩擦系数 ,其耐磨性也更好。     

Fabrication of high chromium cast iron and medium carbon steel bimetal by liquid–solid casting in electromagnetic induction field

The high chromium cast iron and medium carbon steel bimetal was fabricated by liquid–solid casting in electromagnetic induction field. The interfacial structure and mechanical properties were investigated. The results show that the microstructure is refined obviously and mechanical properties are improved significantly. The electromagnetic stirring can refine effectively the microstructure, and profit the diffusion of elements and obtaining of the desirable microhardness transition. The electromagnetic induction heating is beneficial to achieving metallurgical interface bonding and improving the mechanical property. Furthermore, the electromagnetic stirring compels the molten metal to scour continuously the surface of medium carbon steel, resulting in the oxides and impurities being melted or broken away from the surface.     

Microstructure and Properties of Low Temperature Composite Chromized Layer on H13 Tool Steel

Low temperature composite chromizing is a process composed of a plain ion-carbonitriding or ion-nitriding at 550～580℃, followed by a low-temperature chromizing in a salt-bath of 590℃. The microstructure and properties of the low temperature composite chromized layer on H13 tool steel were investigated using metallography,X-ray diffraction, microanalysis, hardness and wear tests. It was found that this low temperature process was thermodynamically and kinetically possible, and the composite chromized layer on H13 steel, with a thickness of 3～6μm,consisted of three sub-layers (bands), viz. the outer Cr-rich one, the intermediate (black) one, and the inner, original white layer. After chromizing, the former diffusion layer was thickened. The results of X-ray diffraction showed that the composite chromized layer contained such nitrides and carbides of chromium as CrN, Cr2N, (Cr, Fe)23C6, and (Cr, Fe)7C3, as well as plain α-(Fe, Cr). A high surface microhardness of 1450～1550 HV0.025, which is much higher than that obtained by the conventional ion carbonitriding and ion nitriding, was obtained. In addition, an excellent wear resistance was gained on the composite chromized layer.     

B4C包覆ZTA颗粒增强铁基复合材料制备与性能

ZTA (ZrO₂增韧Al₂O₃)陶瓷颗粒表面包覆B₄C微粉,将其制备成蜂窝状结构陶瓷预制体。采用传统重力浇注工艺将陶瓷预制体与熔融的高铬铸铁(HCCI)金属溶液进行复合,获得ZTA陶瓷颗粒增强高铬铸铁基复合材料。对复合材料中ZTA陶瓷颗粒增强相与高铬铸铁基体之间的界面及复合材料的耐磨料磨损性能进行了研究。结果表明,ZTA陶瓷颗粒与高铬铸铁界面结合处形成了明显的过渡区域,界面过渡区域的存在提高了陶瓷颗粒与金属基体的结合,从而提升了复合材料的整体稳定性能。同时,三体磨料磨损试验表明该复合材料的耐磨料磨损性能是高铬铸铁的3.5倍左右。     

Verschleißbeständige Fe‐Basislegierungen mit Niobkarbid

Wear Resistant Fe‐Base Alloys with Niobium Carbide Martensitic Fe‐base alloys from the system Fe‐Cr‐C are widely used as chilled cast irons and tool steels. Because of the low hardness of their FeCr‐carbides this paper reports about new alloys with primarily solidified harder niobium carbides. It focuses on a secondary hardenable welding alloy, a coating material for composite castings, a chilled casting and a corrosion resistant cold work tool steel, which are investigated with respect to their process related microstructure and abrasive wear behaviour.