Abrasive wear behaviors of high velocity arc sprayed iron aluminum composite coatings

The High Velocity Arc Spraying （HVAS） technology was used to prepare Fe-Al composite coatings by the adding of different elements into cored wires to obtain different Fe-Al coatings. The added compounds do great effect on the properties of the composite coatings. The microstructures and abrasive wear performances of the coatings were assessed by transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, and THT07-135 high temperature wear equipment. It was found that the adding of Cr3C2 can greatly increase the room temperature wear behavior, and Fe-Al/WC coatings have adapting periods at the beginning of wear experiment. With the rise of temperature, the wear resistance of Fe-AI/Cr3C2 coatings becomes bad from room temperature to 250℃, and then stable from 250℃ to 550℃; the wear resistance of Fe-Al/WC becomes well with the rise of temperature. The adding of Cr and Ni can also improve wear performances of Fe-Al composite coatings.     

Crystallization behavior of plasma-sprayed lanthanide magnesium hexaaluminate coatings

LaMgAl11O19 thermal barrier coatings （TBCs） were prepared by atmospheric plasma spraying. The crystallization behavior of the coatings and the synthesis mechanism of LaMgAl11O19 powders were researched. The results showed that the plasma-sprayed coatings conmined some amorphous phase, and LaMgAl11O19 powders were partially decomposed into Al2O3, LaAlO3, and MgAl2O4 in the plasma spraying process. The amorphous phase was reerystallized at a temperature of approximately 1174.9℃, at which level the decomposed Al2O3, LaAl2O3, and MgAl2O4 reacted again. The resynthesis temperature of LaMgAl11O19 in the plasma-sprayed coatings was lower than that of LaMgAl11O19 in the original raw powders. The synthesis mechanism of LaMgAl11O19 powders can be summarized as follows： during the first part of the overall reaction, La2O3 reacts with Al2O3 to form LaAl2O3 at approximately 900℃, and then LaAl2O3 further reacts with Al2O3 and MgAl2O4 to produce LaMgAl11O19 at approximately 1200℃.     

Al2O3陶瓷与铸铁副在空气和蒸馏水润滑下的滑动磨损

在室温、干摩擦(空气)及蒸馏水润滑条件下使用环块磨损试验机进行Al2O3陶瓷和球墨铸铁、灰铸铁及钢配副时的滑动磨损试验.结果表明:蒸馏水润滑下Al2O3及铸铁的磨损体积均小于在干磨擦条件下;在同一润滑条件下,钢的磨损体积大于铸铁磨损体积,球墨铸铁磨损体积最小;陶瓷Al2O3磨损体积在干摩擦时与铸铁配副时比与钢配副时要小得多.对Al2O3磨面进行形貌及能谱分析,发现在干摩擦条件下,Al2O3磨面有大量铸铁或钢的转移物组成的迁移膜,在蒸馏水润滑条件下则没有.分析认为,铸铁中石墨在于摩擦时能起到较明显的固体润滑剂作用,相对地减小了磨损,而在蒸馏水润滑下石墨的润滑作用己大大减弱.     

水润滑下陶瓷与灰铸铁副的滑动磨损特性

研究了在蒸馏水润滑下Si3N4、Al2O3陶瓷与灰铸铁副的摩擦磨损特性。结果表明：Al2O3陶瓷的磨损体积损失远小于Si3N4的,但灰铸铁与Si3N4配副时的磨损体积损失却大大小于与Al2O3配副时的,其摩擦系数也很小（0．02）。用SEM观察磨损形貌,发现灰铸铁与Si3N4配副时Si3N4磨面极其光滑,与其对应的灰铸铁磨面上存在含石墨的润滑膜。     

Wear behavior of bainite ductile cast iron under impact load

The dry impact wear behavior of bainite ductile cast iron was evaluated under three different impact loads for 30000 cycles. The strain-hardening effects beneath the contact surfaces were analyzed according to the surfaces＇ micro-hardness profiles. Scanning electron microscopy （SEM） and X-ray diffraction （XRD） were used to observe the wom surfaces. The results indicated that the material with the highest hardness was the one continuously cooled at 20℃, which exhibited the lowest wear rate under each set of test conditions. The hardness of the worn surface and the thickness of the hardened layer increased with the increases in impact load and in the number of test cycles. The better wear performance of the sample cooled at 20℃ is attributed to its finer microstructure and superior mechanical properties. All the samples underwent the transformation induced plasticity （TRIP） phenomenon after impact wear, as revealed by the fact that small amounts of retained austenite were detected by XRD.     

铬锰系铸钢的炭含量对磨料磨损性的影响

本文研究了铬锰系铸钢炭含量对磨料磨损性的影响.结果表明,钢的磨损率随炭含量的增加而降低,特别是经800℃时效处理,其降低倾向更大。在采用玻璃砂纸时,时效处理更显出其良好效果。     

Characterization and wear behavior of WC-0.8Co coating on cast steel rolls by electro-spark deposition

To prepare high wear resistance and high hardness coatings, electro-spark deposition was adopted for depositing an elec trode of a mixture of 92wt%WC+8wt%Co on a cast steel roll substrate. The coating was characterized by classical X-ray diffracto meter (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX). The results indicate that the coating shows nanosized particulate structure and dendritic structure including columnar structure and equiaxed structure. The pri mary phases of the coating contain Fe_3W_3C, Co_3W_3C, Fe_2C and Si_2W. The coating has a low friction coefficient of 0.13, its average wear-resistance is 3.3 times that of the cast steel roll substrate and the main mechanism is abrasive wear. The maximum microhard ness value of the coating is about 1573.9 Hv_(0.3) The study reveals that the electro-spark deposition process has the characteristic of better coating quality and the coating has higher wear resistance and hardness.     

Effect of electromagnetic stirring on the microstructure and wear behavior of iron-based composite coatings

The effect of electromagnetic stirring on the microstructure and wear behavior of coatings has been investigated. A series of iron-based coatings were fabricated by the plasma-transferred arc cladding process by applying different magnetic field currents. The microstructure and wear resistance of the composite coatings were characterized by scanning electron microscope (SEM), energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), and wet sand rubber wheel abrasion tester. The experimental re- sults showed that the microstructure of the coatings was mainly the γ-Fe matrix and (Cr, Fe)7C3 carbide reinforced phase. The coatings were metallurgically bonded to the substrate. With increasing magnetic field current, the amount of the block-like (Cr, Fe)7C3 carbide reinforced phase increased at first, reached a local maximum, and then decreased sharply. When the magnetic field current reached 3 A, the block-like (Cr, Fe)7C3 carbides with high volume fraction were uniformly distributed in the matrix and the coating displayed a high microhardness and an excellent wear resistance under the wear test condition.     

高炉HT与QT冷却壁解剖及破损行为比较研究

采用高炉扒炉调查、破损冷却壁实体解剖、统计分析、试验研究等方法,对分别使用灰铸铁（ＨＴ）与球墨铸铁（ＱＴ）材质的马钢３＾＃和１３＾＃高炉冷却壁的宏观破损规律与成因,以及微观破损机制等进行了比较研究。总结提出了６个方面的长寿改进对策。     

球墨铸铁和可锻铸铁的断裂韧性的研究

用Ｊ积分方法研究球墨铸铁和可锻铸铁的断裂韧性可以满足其有效性，并对它们的断裂韧性进行比较，试验结果表明他们的断裂韧性各有特点，在机伯设计过程中充分考虑其断裂韧性是十分必要的。     

贝氏体型白口铸铁组织结构及其抗磨料磨损特性的研究

本文应用光学显微镜、电子显微镜、扫透电子显微镜和X-射线衍射仪对贝氏体型白口铸铁的组织结构和形态进行了观察和测试,同时还对上、下贝氏体在不同试验条件下的抗磨性和残余奥氏体在磨损过程中的行为进行了研究。     

Sialon陶瓷的磨粒磨损行为

Sialon陶瓷的磨粒磨损行为研究结果显示：较高载荷作用下,磨损量随时间呈指数关系增加;较低载荷作用下,磨损初期有一个短暂的磨损量基本不变的孕育阶段,随后进入快磨损阶段,对该孕育现象进行了探讨,通过实验表明,磨损量与转速有线性关系但与载荷无线性关系,SEM对磨损表面分析发现,Sialon陶瓷在SiC磨粒作用下的磨损机理主要是犁耕和表面断裂脱落。     

铝合金上电沉积Ni-P-CNTs复合镀层及其摩擦性能研究

采用复合电沉积法在铝合金表面上制备了镍 磷 碳纳米管（Ni-P-CNTs）复合镀层,并用X射线衍射（XRD）和扫描电镜（SEM）对其进行了表征,分析了电流密度和镀液中碳纳米管的质量浓度对复合镀层形貌及其摩擦磨损性能的影响.当电流密度为3.0 A/dm2时可以得到表面光亮、平整的复合镀层,复合镀层中碳纳米管体积分数随着镀液中碳纳米管质量浓度的增加而增加.Ni-P-CNTs复合镀层比Ni-P镀层具有更高的硬度、耐磨性能和更低的摩擦系数.随着复合镀层中碳纳米管体积分数的增加,复合镀层的磨损量和摩擦系数逐渐降低.复合镀层摩擦性能的改善是由于碳纳米管具有优异的力学性能和良好的自润滑性能.     

Influence of Re-Ti modification on the high impact wear resistance of high Si bainitic cast steel

The effect ofrare earth(Re)and titanium(Ti)multi-modification on the impact wear behavior of Mn-B high-Si bainitic cast steel was investigated systematically.The experiments show that the impact wear resistance can be improved greatly with the addition of Re and Ti.Its wear loss is only about 1/3-1/2 as large as that of the unmodified bainitic cast steel.By the Re/Ti modification,coarse dendrite grains and bainitic/martensite duplex structure have been refined effectively,and the impact toughness ofthe bainitic cast steel is nearly tripled(10mm×10 mm×55 mm with unnotched sample).Consequently,the modified bauutic cast steel possesses good wear resistance under high impact.For both modified and unmodified bainitic cast steels,high hardness white layer and deformed zone are developed beneath the worn surface under the lugh impact wear,but the formation and propagation of cracks are different for these bainitic casting steels.Different models for the formation and propagation of cracks for both modified and unmodified bairutic cast steels under high impact wear are proposed.     

铸铁中渗碳体高温石墨化研究

为了解决离心球墨铸铁管自由渗碳体墨化问题，研究了白口铁石墨化形核，长大机理，计算了渗碳体石墨化驱动力及恒温转动力学，通常光学金相和电子显微分析发现，石墨可以在奥氏体中，渗碳体及奥氏体与渗碳体的相界面形核，而在奥氏体中形核几率较大，计算结果表明，硅大大地提高了石墨化驱动力，高温石墨化动力学较好地符合Avrami方程。     

夹杂物对Cr13铸钢耐磨性的影响

本文研究了动载磨损条件下夹杂物的数量、形态与分布对铸钢耐磨性的影响及其作用机理．试验表明，夹杂物在动载磨粒磨损过程中的作用与磨损机理密要相关，夹杂物的存在，增加了裂纹形核的机率，导致磨损率增加．减少夹杂物的数量，改善夹杂物的形态与分布能提高铸钢的耐磨性     

改善白口铸铁抗磨性的途径

综述了国内外改善白口铸铁抗磨性的途径,合理选择其基体组织,改善碳化物的形态及分布。并对后者从塑性变形、变质处理、热处理、合金化等四个方面及其特点作了探讨。     

直读光谱分析在合金铸铁中的应用

介绍了利用美国ＡＲＬ３４６０直读光谱仪进行铬钼铜合金铸铁分析的实验方法。结果表明，在３４６０仪上，白口化合金铸铁可以得到准确测定。并就主要因素氩气纯度，试样制备，磨料质量，开机时间等对分析精度、准确度的影响作了讨论。     

等离子喷涂梯度涂层的显微组织结构和性能

针对低散热发动机主要部件铝活塞顶部制备热障涂层的需要，用等离子喷涂法在铝基体上制备出梯度涂层，对其性能与显微组织结构进行了研究．抗热震实验结果表明，梯度涂层具有较高的结合强度．金相显微观测结果表明，梯度热障层结构致密，由基体至涂层表面。形成5种无宏观结合界面的成分呈梯度变化的组织结构．     

白口铸铁的磨料磨损行为及耐磨性

通过白口铸铁的耐磨试验，观察分析材料的磨面和磨屑；研究不同性能的白口铸铁在磨料磨损时的行为机理．