含硼高铬铸铁的组织及性能

在成分为2.7%C-17%Cr-0.7%M_0的高铬铸铁中设计了含硼量变化范围为0.1～1.2%的五种白口铸铁.考察了其铸态及热处理态的组织;进行了石英砂磨料和绿碳化硅磨料的三体磨损试验及湿式橡胶轮磨损试验;测定了材料的硬度、冲击韧性和断裂韧性.试验结果表明:硼促使化合物体积分数增加,并有新的硼碳化物形成;基体组织中铸态己有马氏体析出,具有更好的淬硬性;三体磨损石英砂磨料时随含硼量增加耐磨性显著提高,对碳化硅磨料则相反;在湿式橡胶轮磨损试验中约在0.9%B 处耐磨性出现了最大值;化合物量相近时,含硼与无硼高铬铸铁的韧性相当.     

复合变质高铬铸铁

通过添加不同含量的V，RE合金元素，对普通高铬铸铁进行复合变质处理，研究其显微组织，机械性能及抗磨性，得出：经V，RE复合变质的高铬铸铁，可使碳化物转变为弧立的块状，冲击韧性和抗磨性均提高，当含0．255V，0．7％RE时，ak约提高60％，抗磨性约提高二倍。     

重熔时间对半固态过共晶高铬铸铁初生相的影响

为考察触变重熔时间对初生碳化物形貌的影响，对Cr17过共晶高铬铸铁半固态坯料在1270℃进行了部分重熔，重熔时间分别为5、15、25和30min，并借助Leica图像分析仪分别定量描述了碳化物形状因子及粒度因子的变化规律．研究表明：碳化物形貌的演化过程包括3个阶段，即熔断阶段、球化和细化阶段及合并长大阶段；碳化物演化过程是溶质原子扩散和相界面张力共同作用的结果，且分别在触变重熔初期和中后期占主导地位；在1270℃部分重熔15min，可获得理想的重熔组织．     

复合变质剂对高铬铸铁篦条组织的影响

通过金相显微镜和扫描电镜观察,研究Ti-W-Mg、Ti-Zr-Nb、Ti-Zr-Y基重稀土3种复合变质剂对高铬铸铁篦条组织的影响。结果表明,经变质处理后的篦条铸态组织中,其初生奥氏体被不同程度等轴化,共晶碳化物被有效细化、圆整化、孤立化和弥散化;篦条韧性有不同程度的增强;3种复合变质剂对高铬铸铁篦条组织的影响效果为:Ti-W-Mg最佳,Ti-Zr-Y基重稀土次之,Ti-Zr-Nb最差。     

稀土铬硼抗磨铸铁的研制与应用

本文在实验室和工厂条件下研制了与高铬铸铁磨球相匹配的衬板新材质—稀土铬硼抗磨铸铁，取代传统应用的高锰钢（ZGMn13）衬板，使用寿命提高1～2倍．     

硼碳共渗剂中木炭作用的研究

本文研究了以渗硼为基的固体硼碳共渗处理。结果证明,木炭对渗硼有一定的催化作用。当共渗剂中的木炭和硼铁含量控制适当时,可获得性能较好的Fe_2B单相渗层;而且渗层增厚,过渡区增加,使硬度梯度减缓,硼化物层的脆性降低。此外,共渗剂的生产成本下降,提高了经济效益。     

高强度合金硼铸铁组织成分与切削性能研究

摘要：
合金硼铸铁具有高硬度、高强度以及良好的耐磨性和耐热性,是高速机车柴油机气缸套的主流材料.文中对气缸套合金硼铸铁的显微组织结构、化学成分和车削加工性能进行了分析评估.结果表明：合金硼铸铁的石墨形态以高强度A型石墨为主;与非涂层和氮铝钛涂层硬质合金刀具相比,赛隆（Sialon）陶瓷刀具具有更优良的性能,可以实现合金硼铸铁气缸套的高效加工. 关键词：
合金硼铸铁; 车削; 刀具磨损; 氮铝钛涂层; 赛隆陶瓷 中图分类号： TG 113
文献标志码： A     

电磁搅拌对高Cr白口铸铁组织形成的影响

文章研究了电磁搅拌对高Cr白口铸铁凝固结晶的影响。结果表明:电磁搅拌对高Cr白口铸铁组织改善明显,随励磁电压增大,电磁搅拌作用增强,初晶奥氏体由树枝状枝晶变为球状或不规则的碎块状,得到充分细化;共晶碳化物由大板条变为细小的短杆状、碎块状、菊花状,分布更加均匀。     

烧结亚共晶高铬铸铁制备及其显微组织与性能

以水雾化高铬铸铁粉末为原料,通过压制/烧结工艺制备了一种亚共晶高铬铸铁(SHCCI),对其显微组织、物理力学性能和冲击磨粒磨损工况下的耐磨性能开展了系统的观察、分析与检测,并与成分相近的传统铸造高铬铸铁(CHCCI)进行了对比研究.试验结果表明,通过超固相线液相烧结可以制备出密度达到7.44g/cm~3的亚共晶高铬铸铁,其Cr_7C_3型碳化物呈细小短杆状,沿晶界均匀地分布在由马氏体和奥氏体混合组成的基体中;烧结态高铬铸铁的硬度为HRC58,抗弯强度为2 122MPa,冲击韧性达到6.5J/cm~2(无缺口试样尺寸为5mm×5mm×50mm);与铸造高铬铸铁相比,由于碳化物形貌、大小和分布均匀性的明显改善,以及基体中有更多的马氏体,烧结高铬铸铁在各种冲击载荷下均展现出明显的抗磨粒磨损性能优势,是一种十分优异的耐磨材料.     

锻造加热处理对高硼铸造铁基合金组织与性能的影响

采用锻造+热处理复合工艺消除高硼铸造铁基合金中硼化物的连续网状分布,显著提高了合金的韧性.借助扫描电镜、透射电镜和X射线衍射仪等手段分析了锻造+热处理对高硼铸造铁基合金组织与性能的影响,结果表明:锻造使网状硼化物破断,获得了均匀分布在基体中的条块状硼化物,硼化物局部出现"颈缩"和亚晶界;经热处理后,硼化物尖角圆整化,而存在"颈缩"部位和亚晶界的硼化物则断开和球化;经锻造+热处理复合工艺处理后,合金的宏观硬度略有增加,由HRC51.4增加到HRC54.7,冲击韧性则大幅度提高,由5J/cm2提高到107J/cm2,增加了约21倍,冲击断口由脆性断口转变为韧性断口.     

Microstructure evolution in grey cast iron during directional solidification

The solidification characteristics and microstructure evolution in grey cast iron were investigated through Jmat-Pro simulations and quenching performed during directional solidification. The phase transition sequence of grey cast iron was determined as L → L + γ → L +γ + G → γ + G → P (α + Fe₃C) + α + G. The graphite can be formed in three ways:directly nucleated from liquid through the eutectic reaction (L → γ + G), independently precipitated from the oversaturated γ phase (γ → γ + G), and produced via the eutectoid transformation (γ → G + α). The area fraction and length of graphite as well as the primary dendrite spacing decrease with increasing cooling rate. Type-A graphite is formed at a low cooling rate, whereas a high cooling rate results in the precipitation of type-D graphite. After analyzing the graphite precipitation in the as-cast and transition regions separately solidified with and without inoculation, we concluded that, induced by the inoculant addition, the location of graphite precipitation changes from mainly the γ interdendritic region to the entire γ matrix. It suggests that inoculation mainly acts on graphite precipitation in the γ matrix, not in the liquid or at the solid-liquid front.     

Microstructure and high-temperature wear properties of in situ TiC composite coatings by plasma transferred arc surface alloying on gray cast iron

In this work, an in situ synthesized TiC-reinforced metal matrix composite (MMC) coating of approximately 350–400μm thick-ness was fabricated on a gray cast iron (GCI) substrate by plasma transferred arc (PTA) surface alloying of Ti–Fe alloy powder. Microhard-ness tests showed that the surface hardness increased approximately four-fold after the alloying treatment. The microstructure of the MMC coating was mainly composed of residual austenite, acicular martensite, and eutectic ledeburite. Scanning electron microscopy (SEM) and X-ray diffraction analyzes revealed that the in situ TiC particles, which were formed by direct reaction of Ti with carbon originally contained in the GCI, was uniformly distributed at the boundary of residual austenite in the alloying zone. Pin-on-disc high-temperature wear tests were performed on samples both with and without the MMC coating at room temperature and at elevated temperatures (473 K and 623 K), and the wear behavior and mechanism were investigated. The results showed that, after the PTA alloying treatment, the wear resistance of the sam-ples improved significantly. On the basis of our analysis of the composite coatings by optical microscopy, SEM with energy-dispersive X-ray spectroscopy, and microhardness measurements, we attributed this improvement of wear resistance to the transformation of the microstruc-ture and to the presence of TiC particles.     

铬系耐磨铸铁的摩擦金属学行为与纳米改性

在我国,每年设备、配件的使用磨损、腐蚀及表面失效造成材料损失高达上亿万吨,为了提高耐磨材料的性能,将宏观的摩擦磨损现象与金属组织的微观变化相联系,用动态金属学的观点研究磨损的微观机制,即进行摩擦金属学研究,是揭示金属材料磨损本质的基本途径,有助于耐磨材料和耐磨处理方法的选择和研究开发。基于对高Cr、低Cr和Cr-Mo-Cu耐磨铸铁所进行的摩擦金属学研究,结果表明:利用纳米改性技术可以改善铬系耐磨铸铁的组织结构和性能,尤其是提高铬系耐磨铸铁的耐磨性方面效果明显。该研究为高铬铸铁和Cr-Mo-Cu合金铸铁等材料耐磨性能的提高提供了一条有效途径。     

蠕墨铸铁凝固过程中的共晶生长模式

研究蠕墨铸铁凝固过程中的共晶生长模式,探索不同共晶生长模式与铸造凝固特性的关系,为蠕墨铸铁件的工艺设计及生产提供供理论依据。     

The Microstructure of Graphite Spherulites in Cast Iron

The microstructure of graphite spherulites (G.S.) in Ce addition ductile cast iron was carried out using transmission electron microscopy (TEM) techniques. The structral characterization of the graphites is as following: there are platelets growing along the periphery as well as fan-like structure formed from platelet aggregates in the diameter section of spherulite, in which most of the platelets are with sizes ranging from several to tens nm in radial; the [001] direction of the platelets would have a tend to parallel to radial of the G. S. and meanwhile, they also a small misorientation deviated from the radial among the platelets each other. It shows that the anisotropy of graphites has been restrained by adding Ce element in cast iron and the structural characterization of the G. S. is consistent with the Double' s model of the conical helixes formed in helical growing and branching.     

等温淬火高硅铸钢的显微组织和机械性能

为开发一种新型高硅耐磨铸钢 ,采用扫描电子显微镜研究了不同等温温度下高硅铸钢的显微组织 ,对不同等温温度下高硅铸钢的抗拉强度、冲击韧性和硬度进行了系统研究。结果表明 ,高硅铸钢经等温淬火热处理后 ,在较大的温度范围 (2 4 0～ 4 0 0℃ )内都可以得到单一的由贝氏体铁素体和富碳的残余奥氏体交替排列的奥贝双相组织 (Ausferrite) ,组织中没有碳化物析出。在 2 80～ 3 60℃范围内等温 ,可以获得强度、韧性、硬度配合良好的双相组织。高硅铸钢具有优异的综合机械性能 ,同时具有良好的冷作硬化能力