Wear resistance of ductile irons

This study was undertaken to evaluate the wear resistance of different grades of ductile iron as alterna-tives to high- tensile- strength alloyed and inoculated gray irons and bronzes for machine- tool and high-pressure hydraulic components. Special test methods were employed to simulate typical conditions of reciprocating sliding wear with and without abrasive- contaminated lubricant for machine and press guideways. Quantitative relationships were established among wear rate, microstructure and micro-hardness of structural constituents, and nodule size of ductile iron. The frictional wear resistance of duc-tile iron as a bearing material was tested with hardened steel shafts using standard test techniques under continuous rotating movement with lubricant. Lubricated sliding wear tests on specimens and compo-nents for hydraulic equipment and apparatus were carried out on a special rig with reciprocating motion, simulating the working conditions in a piston/cylinder unit in a pressure range from 5 to 32 MPa. Rig and field tests on machine- tool components and units and on hydraulic parts have confirmed the test data.     

Eutectic modification in a low-chromium white cast iron by a mixture of titanium,rare earths,and bismuth: Part II. effect on the wear behavior

In this work, we studied the wear behavior of a low-Cr white cast iron (WCI) modified with ferrotitanium-rare earths-bismuth (Fe-Ti-RE-Bi) up to 2%. These additions modified the eutectic carbide structure of the alloy from continuous ledeburite into a blocky, less interconnected carbide network. The modified structure was wear tested under pure sliding conditions against a hardened M2 steel counter-face using a load of 250 N. It was observed that wear resistance increased as the modifier admixture increased. The modified structure had smaller more isolated carbides than the WCI with no Fe-Ti-RE-Bi additions. It was observed that large carbides fracture during sliding, which destabilizes the structure and causes degradation in the wear behavior. A transition from abrasive to oxidative wear after 20 km sliding occurred for all alloys. In addition, the modified alloys exhibited higher values of hardness and fracture toughness. These results are discussed in terms of the modified eutectic carbide microstructure.     

高钒高速钢干滑动磨损性能研究

利用MM-200型滑动磨损试验机测试了高钒高速钢在不同压力下的干滑动磨损性能，借助于扫描电镜对其磨损形貌和组织进行观察，并与高铬铸铁对比考察了其耐磨性和磨损机理。结果表明：高钒高速钢的耐磨性明显优于高铬铸铁，其磨损机理为犁削磨损和疲劳磨损的复合，并且有应力作用下碳化物的脆性碎裂及脱落。     

低碳球墨铸铁冲击磨料磨损特性的研究

研究经准铸态贝氏体工艺处理低碳球墨铸铁冲击磨料磨损特性。采用消失模铸造工艺，经准铸态贝氏体工艺处理后，得到了贝氏体组织。冲击磨料磨损过程以冲击变形磨损为主，兼有切削磨损和凿削磨损。通过在水泥厂应用，结果表明：磨球的成本可比低铬合金铸铁磨球降低18％，而磨球的吨水泥磨耗还不到后者的80％，破球率降低了50％。     

高速球铣路径对淬硬钢SKD11表面摩擦特性的影响

通过高速铣削试验与环-块摩擦磨损试验,借助白光干涉仪、超景深三维显微镜、显微硬度计等分析检测设备,研究了走刀路径对淬硬模具钢SKD11表面摩擦特性的影响。结果表明:球铣加工表面摩擦特性具有方向性,当走刀方向与摩擦方向垂直时,摩擦因数最小,磨痕宽度最窄,当二者夹角成45°时,摩擦因数最大,磨痕宽度最宽。球铣走刀路径影响加工表面形貌取向,表面形貌通过改变接触应力和磨屑捕捉能力来影响犁耕效应和黏着效应,进而影响摩擦特性。干摩擦工况下,主要磨损机理是磨粒磨损与氧化磨损,试验15 min后表面微沟槽形貌均已消失;而润滑工况下,表面微沟槽依然清晰,走刀路径与摩擦方向夹角成0°与45°试样表面出现磨粒磨损特征,而夹角成90°试样表面无明显划痕,表明采用该路径进行球铣加工具有较好的减磨效果。     

奥贝球铁齿轮在柴油机上的应用研究

研究了不同等温温度及Mn、Si、Cu、Mo对奥贝球铁组织和力学性能的影响,讨论了奥贝球铁加工硬化对机加工性能的影响。同时,奥贝球铁齿轮代替40Cr调质钢齿轮进行装机试验,对降噪声和耐磨性进行了测试。结果表明,奥贝球铁齿轮与40Cr调质钢齿轮相比,力学性能高,柴油机整机噪声下降1.92dB,齿轮侧噪声下降5.3dB,奥贝球铁齿轮经过45h磨合后,在标定工况下连续运转200h,齿轮无异常磨损,齿轮间隙离极限间隙还有0.13mm的余量,所以其摩擦磨损性能合格,所生产的奥贝球铁齿轮满足设计使用要求。     

The influence of the microstructure of hardened tool steel workpiece on the wear of PCBN cutting tools

Due to the recent developments of advanced cutting tool materials in the superbarasive family, such as cubic boron nitride (CBN) tools, the interest in cutting hardened steels has increased significantly. High flexibility and ability to manufacture complex workpiece geometry in one set up is the main advantage of hard turning compared to grinding. The focus of this study is to investigate the performance and wear behavior of CBN tools in finish, dry turning of four different hardened steels, treated to the same hardness R_c = 54. The following four materials were machined: X155CrMoV 12 cold work steel (AISI D2), X38CrMoV5 (AISI H11) hot work steel, 35NiCrMo16 hot work steel and 100Cr6 bearing steel (AISI 52100). A large variation in tool wear rate was observed in the machining of these steels. The tool flank grooves have been correlated to the microstructure of these steels, namely the presence of various carbides. The chip study reveals that there is presence of different amounts of white layers in machining these steels.     

高钒高速钢干滑动磨损性能研究

利用MM-200型滑动磨损试验机测试了高钒高速钢在不同压力下的干滑动磨损性能,借助于扫描电镜对其磨损形貌和组织进行观察,并与高铬铸铁对比考察了其耐磨性和磨损机理。结果表明:高钒高速钢的耐磨性明显优于高铬铸铁,其磨损机理为犁削磨损和疲劳磨损的复合,并且有应力作用下碳化物的脆性碎裂及脱落。     

Microstructure and Mechanical Properties of a Wear-Resistant As-Cast Alloyed Bainite Ductile Iron

An as-cast bainite ductile iron with excellent mechanical properties and wear resistance was fabricated by alloying and centrifugal casting method, and the alloyed chemical composition was optimized by using the thermodynamic software Thermo-Calc. By using optical microscopy, transmission electron microscopy, scanning electron microscopy, and X-ray diffraction, the microstructure of the as-fabricated bainite ductile cast iron was characterized pertinent to the elements distribution in matrix and features of ferrite and retained austenite. The results of mechanical properties test show that the hardness and compressive strength of this alloyed ductile iron are 52 HRC and 2,200 MPa, respectively. The ascast bainite ductile iron possesses highly abrasive wear resistance and the reason can be ascribed to the solid solution of the elements Si, Ni, Cu, and Mn in the austenite and the formation of carbides of elements Cr and Mo. The strength of bainite ductile iron is increased by the acicular bainitic ferrite in the matrix.     

Effects of microstructure and strength on wear performance in rough milling of austempered ductile iron

The machinability of various grades of austempered ductile iron (ADI) has been investigated for rough milling operations. ADI 900, ADI 1050 and ADI 1200 grades were commercially produced, commercially heat treated and machined under controlled conditions using coated carbide inserts with coolant in the laboratory. The milling performance of the various grades was compared to that of AISI/SAE 4340 with similar hardness. In this study, machinability characteristics relative to wear rate (ISO 8688-2) and machining forces were measured and related to initial microstructure and properties. These preliminary results have been used to establish initial rough milling machining guidelines for machining ADI with coated carbide milling inserts.     

蠕墨铸铁的干滑动摩擦学特性

分析了蠕墨铸铁的干滑动摩擦磨损规律，研究了工况条件（速度，压力）、成分、组织对蠕墨铸铁干滑动摩擦学特性的影响，探讨了蠕墨铸铁摩擦表面三维形貌与摩擦表而温度特性，结果表明：蠕墨铸铁与球墨铸铁和灰铸铁相比具有最低的磨损率和最高的摩擦系数与最低的摩擦系数衰减最，适合于作为制动器材料。在蠕墨铸铁中添加P、Cr等合金元素可以显著提高耐磨性能。增加摩擦系数。通过对试样三维表面形貌和干滑动摩擦温度场分析．进一步从机理上解释了蠕墨铸铁所具有的良好干滑动摩擦学性能。     

我国等温淬火球铁(ADI)生产应用及发展前景

概述了我国等温淬火球铁的生产应用情况,指出我国等淬球铁主要用于三个方面:1)普通抗磨零件,如磨球、衬板、锤头、锤片等;2)承载构件,如斜楔、销套、小型柴油机曲轴等;3)高性能、高精度要求的重要构件,如多缸柴油机曲轴和各类齿轮等。分析了我国等淬球铁扩大应用和工业化生产发展缓慢的主要原因是:1)对等淬球铁的优异性能宣传不够,没有相应的标准提供给设计者;2)大部分球墨铸铁生产厂不能稳定地提供符合等淬球铁要求的球铁铸件;3)缺乏专业的等淬球铁热处理厂和性能先进、稳定的等淬热处理装备。预测了我国等淬球铁的发展前景并对今后工作提出了建议。     

奥贝球铁磨粒磨损性能的研究

奥贝球铁磨粒磨损性能的研究郭新立，孟祥康，刘治国，董鄂（南京大学）（南京理工大学）奥贝球铁是新一代的球墨铸铁，与普通球铁相比，奥贝球铁具有较高的强度、韧性、抗点蚀疲劳、弯曲疲劳和耐磨性能，被视为７０年代以来铸铁冶金的重大突破￣［１、４］。其应用目标之...     

高碳低合金耐磨钢的试验研究

对所研制的高碳低合金耐磨钢的强韧化、耐磨性及磨损行为进行了研究。结果表明,在中、低冲击磨料磨损条件下,试验钢的耐磨性优于中碳低合金耐磨钢和高锰钢。     

Wear Behavior of an Ultra-High-Strength Eutectoid Steel

Wear behavior of an ultra-high-strength AISI 1080 steel developed through incomplete austenitization-based combined cyclic heat treatment is investigated in comparison with annealed and conventional hardened and tempered conditions against an alumina disk (sliding speed = 1 m s^?1) using a pin-on-disk tribometer at a load range of 7.35-14.7 N. On a gross scale, the mechanism of surface damage involves adhesive wear coupled with abrasive wear (microcutting effects in particular) at lower loads. At higher loads, mainly the abrasive wear (both microcutting and microploughing mechanisms) and evolution of adherent oxide are observed. Besides, microhardness of matrix increases with load indicating substantial strain hardening during wear test. The rate of overall wear is found to increase with load. As-received annealed steel with the lowest initial hardness suffers from severe abrasive wear, thereby exhibiting the highest wear loss. Such a severe wear loss is not observed in conventional hardened and tempered and combined cyclic heat treatment conditions. Combined cyclic heat-treated steel exhibits the greatest wear resistance (lowest wear loss) due to its initial high hardness and evolution of hard abrasion-resistant tribolayer during wear test at higher load.     

等温淬火球墨铸铁的滑动磨损

研究了奥贝球铁、下贝球铁及与其基体组织相同的钢的滑动磨损性能。实验结果表明 :在一定条件下 ,石墨对等温淬火球铁耐磨性无补而有损。由于奥贝球铁的转折载荷随摩擦速度的提高而增大 ,当转速为 980r/min ,载荷 >6 8 6N时 ,等温淬火球铁的耐磨性优于钢     

WC颗粒增强Cr系白口铸铁复合材料的三体磨损性能的研究

系统研究了在三体磨损条件下,WC颗粒增强Cr系白口铸铁表层复合材料的抗磨损性能,并与相应的Cr系白口铸铁的抗磨损性能进行了比较.结果表明,铸态去应力处理时,Cr系白口铸铁随着金属Cr含量的增加,其耐磨性有所增强;Cr含量从2%增加到26%,相对耐磨性从1增加到1.39,而复合材料相对于基体材料的耐磨性提高到了6以上.硬化态去应力处理时,Cr系白口铸铁随着金属Cr含量的增加,其耐磨性略有增强;Cr含量从2%增加到26%,相对耐磨性从1增加到1.29,而复合材料相对于基体材料的耐磨性提高到5以上.可见,为了提高Cr系白口铸铁材料表层的耐磨性能,采用制备WC颗粒增强Cr系抗磨白口铸铁表层复合材料的途径十分有效.     

Wear Performance of Cu-Alloyed Austempered Ductile Iron

An investigation was carried out to examine the influence of structural and mechanical properties on wear behavior of austempered ductile iron (ADI). Ductile iron (DI) samples were austenitized at 900 °C for 60 min and subsequently austempered for 60 min at three temperatures: 270, 330, and 380 °C. Microstructures of the as-cast DI and ADIs were characterized using optical and scanning microscopy, respectively. The structural parameters, volume fraction of austenite, carbon content of austenite, and ferrite particle size were determined using x-ray diffraction technique. Mechanical properties including Vicker’s hardness, 0.2% proof strength, ultimate tensile strength, ductility, and strain hardening coefficient were determined. Wear tests were carried out under dry sliding conditions using pin-on-disk machine with a linear speed of 2.4 m/s. Normal load and sliding distance were 45 N and 1.7 × 10⁴ m, respectively. ADI developed at higher austempering temperature has large amounts of austenite, which contribute toward improvement in the wear resistance through stress-induced martensitic transformation, and strain hardening of austenite. Wear rate was found to depend on 0.2% proof strength, ductility, austenite content, and its carbon content. Study of worn surfaces and nature of wear debris revealed that the fine ausferrite structure in ADIs undergoes oxidational wear, but the coarse ausferrite structure undergoes adhesion, delamination, and mild abrasion too.     

凸轮轴磨损的试验研究

研究在干磨损条件下凸轮轴的磨损机制和磨损表面形貌的变化。计数体材料是AISI 1020硼钢。用磨损测试持续时间和负载的函数计算样本质量损失以确定磨损量。凸轮轴轮廓的变化是在磨损过程中由液位传感器获取的。在整个测试过程中,在计算机屏幕上不断监测轮廓变化,以寻求沿接触面变化的凸轮表面磨损机制,最大磨损值只在凸轮的顶部。     

高频淬火对FeNiMoCuCr粉末烧结钢干摩擦磨损性能的影响

采用销盘式磨损试验机研究了FeNiMoCuCr系粉末烧结钢经表面高频淬火后,在干摩擦磨损条件下的磨损性能,并借助于扫描电镜观察和分析了磨损形貌,探讨其摩擦磨损机制。结果表明,试验材料的磨损率在磨损开始阶段,随摩擦滑移距离的增加而增加,而后逐渐趋于稳定;高频淬火处理后的FeNiMoCuCr粉末烧结钢的耐磨性高于烧结未淬火的磨损率,扫描电镜显示干摩擦磨损形貌为微观犁沟和塑性变形,粘着磨损和氧化磨损是主要的磨损机制。