Corrosion of high chrome wear part materials used in vertical roller mills

Abstract

The corrosion resistance of two high chrome wear facings, manganese cold workable steel and heat treated white cast iron, was investigated. The addition of Cl^? to the aqueous solution unexpectedly improves the corrosion resistance. Tribocorrosion experiments show that the current density increases but with magnitudes of no importance in industrial vertical roller mill applications. However, these corrosion magnitudes might show significant material losses in other industrial applications such as marine industries including oil drilling. The investigated wear part materials are not specifically designed to withstand abrasive marine conditions; however, the applied scientific approach might be used on such materials.     

Forming nanostructured hypereutectic aluminum via high-velocity oxyfuel spray deposition

Al-Si alloys are widely used in aerospace and automobile industries due to their high strength-to-weight ratio and superior wear and corrosion resistance. Increasing the percentage of silicon in these alloys improves their wear resistance and strength considerably, but impairs their ductility. This problem can be overcome by refining the microstructure of hypereutectic alloys by varying the processing conditions. High velocity oxyfuel (HVOF) spray deposition is an efficient process to deposit nanostructured Al-Si coatings and near-net-shape spray-formed structures. This article deals with the microstructural evolution in an Al-21wt.% Si alloy processed through HVOF spraying. T. Laha is pursuing his doctoral degree in the same department. For more information, contact A. Agarwal, Florida International University, 10555 West Flagler Street, CEAS 3464, Department of Mechanical and Materials Engineering, Miami, Florida 33174; agarwala@fiu.edu.     

镁合金防腐蚀技术的研究现状及未来发展方向

镁合金由于具有优良的性能而在电子、汽车和航空航天工业得到广泛应用,但其较差的耐腐蚀性能又使其应用受到限制,因此可通过净化合金成分、改变微观结构和采用适当的表面处理方法来改善镁合金的耐腐蚀性能.主要介绍了当前镁合金防腐蚀技术的国内外研究现状,对这些技术进行了评价并指出镁合金各种表面处理技术的优缺点及其未来发展方向.     

Tribological Behavior of Aluminum Slurry Coating on 300M Steel

Al slurry coatings, an alternative of Cd coating to protect against corrosion in the aerospace industry, are currently being explored to satisfy the stringent technology and safety requirements for aeronautical applications. The results of salt fog corrosion exposure, fluid corrosion exposure (immersion), humidity resistance, electrical conductivity, galvanic corrosion, embrittlement, and fatigue indicate that Al slurry coatings can be used as an alternative of Cd coatings. However, the tribological property of Al slurry coatings has still not been investigated. Two types of aluminum slurry coatings on 300M steel were produced using the innovative technological process and characterized by scanning electron microscope, nanoindentation tests, and adhesion tests. The H/E and H ³/E ² ratios of the two-layer Al slurry-coated sample were almost four times higher than the Cd-Ti plating-coated sample. The dry wear test results show that the friction coefficient of the two-layer Al slurry coating independently from the load was lower than the Cd-Ti plating. The width of the wear track of the two-layer Al slurry coating was significantly narrower, only 62% of the Cd-Ti plating wear scar. Compared to the Cd-Ti plating, an excellent wear resistance of the two-layer Al slurry coating can be attributed to its high resistance to plastic deformation and good load-bearing capacity. The results indicate that the two-layer Al slurry coating is an excellent alternative to Cd coatings in the aerospace industry.     

Investigation on Microstructure,Wear Behavior and Microhardness of Al−Si/SiC Nanocomposite

Aluminum matrix nano-composites have been widely used in various fields such as aerospace, automobile, and packing industries. In this study, the effect of nano-SiC content on the microst-ructure, wear resistance and micro-hardness of Al–Si/SiC nano-composite was investigated. In this regard, Al–Si matrix was reinforced by different amounts of nano-SiC: 0, 0.5, 1, 1.5, 3, 5, 10 wt %. The results showed that with increasing the nano-SiC weight ratio, nano-particles are agglomerated and unsuitable sintering increases the porosity, as pores and cavities. For more than 1.5% weight ratio of nano-SiC in the matrix, the wear resistance and the micro-hardness decreased. The results of the wear test, scanning electron microscopy, energy dispersive X-ray spectroscopy and worn surfaces showed that the dominant wear mechanism is controlled by nano-SiC contents. This study indicated that with adding nano-SiC particles more than the optimal content, wear resistance and micro-hardness of Al–Si/SiC nano-composite increased more than twice.     

TiAl金属间化合物表面技术进展

TiAl合金具有低密度、高比强度、高比刚度、高弹性 模量、耐腐蚀和高温抗蠕变性好等优点，成为航空航天、工业燃气轮机以及汽车工业中最具潜力的高温结构材料.作为最接近实用化阶段的一类金属间化合物，须解决其抗高温氧化和耐磨性差的问题.本文综述了TiAl金属间化合物抗高温氧化和耐磨的表面技术最新进展.     

热喷涂技术在国内外的应用（1）

介绍了当今世界十大关键技术之一表面工程学的一个分支－热喷涂技术在国内外的应用情况,着重介绍了其在长效防腐,汽车,钢铁,航空等典型领域的应用情况。     

Zn-Ni合金镀层中添加第三种元素和纳米颗粒的研究新进展

介绍了在汽车、航空航天等行业中得到广泛应用的钢铁零件电镀Zn-Ni合金镀层,以及往碱性、氯化物等锌镍合金镀液中加入Fe、Co、Mn、Ce、P等第三种元素所获得的锌镍三元合金镀层,具有更优良的耐腐蚀性、催化性等性能的情况。介绍了往Zn-Ni合金镀液里加入氧化硅、氧化铈、氧化钛、氧化铝、碳化硅等纳米颗粒的进展情况,发现含有纳米颗粒的锌镍复合镀层具有耐腐蚀性、耐磨损性、热稳定性更好,硬度更高等优点。梳理了2016年以来在Zn-Ni合金电镀中添加第三种元素和纳米颗粒的多层镀层研究新进展。从Zn-Ni单一镀液中沉积Ni-P和Zn-Ni合金多层镀层时,在低电流密度下沉积出Ni-P层;在较高电流密度下,沉积出含3.2%P的Zn-Ni-P合金镀层,这种多层镀层可以大幅度提高钢铁零件的防腐蚀性能。介绍了在含12%Ni的Zn-Ni镀层上镀覆Ni-Co-SiC纳米复合镀层的情况,这种多层结构既可以提高镀层的结合力,又可提高其在3.5%NaCl溶液中的耐腐蚀性能。该复合镀层是一种硬度高、磨损量低的新型Zn-Ni合金复合镀层。     

热喷涂技术替代电镀硬铬的研究进展

从热喷涂技术的发展,高速火焰喷涂(HVOF)涂层的性能,包括耐磨性、耐蚀性、对基体耐疲劳性的影响,热喷涂涂层替代电镀硬铬镀层的成本以及应用4个方面综述了近年来热喷涂技术替代电镀硬铬的研究进展.指出热喷涂技术已经在航空、冶金、包装印刷和造纸等工业领域部分替代了电镀硬铬工艺;由于热喷涂技术对于大工件、厚涂层在性能和价格上的优势,热喷涂技术在其他工业领域的应用也将得到迅速发展.     

Effects of Pb and Cu additives on microstructure and wear corrosion resistance behaviour of PM Al–Si alloys

Abstract

The wear and wear corrosion resistance behaviour of Al–20Si–XPb–YCu (X=0–10 wt-%, Y=0–3 wt-%) alloys fabricated by a powder metallurgy (PM) technique and subsequent heat treatments were evaluated by a block on ring tribotest. The microstructure of all aluminium alloys was observed by optical microscopy and scanning electron microscopy with X-ray energy dispersive spectroscopy. The effects of applied potentials and environments including dry air and 3.5 wt-%NaCl aqueous solution were studied. The results of microstructure analysis indicated that Pb exhibited a bimodal distribution in the Pb containing alloys, and Cu particles become to form the intermetallic phase CuAl₂. Furthermore, the hardness rises significantly for both Pb and Cu containing alloys only after solid solution quenching treatment. The wear and corrosion results showed that the addition of both lead and copper would improve the wear resistance but lead to a higher corrosion rate whereas heat treatment had a beneficial effect of reducing the corrosion rate of most alloys with the exception of Al–Si alloy. Furthermore, by comparison of all alloys after heat treatment, the wear corrosion resistance of Al–Si alloy was inferior to the other alloys; consequent additions of Pb and Cu further improved its wear corrosion resistance. Moreover, at an anodic potential, the wear corrosion rate and current density of both Al–Si and Al–Si–Cu alloys containing particle Pb decrease significantly owing to a corrosion product layer composed of Al, O and Pb elements.     

纳米稀土CeO2掺杂对Ni-Fe-Co-P合金镀层性能的影响

利用喷射电沉积技术制备了Ni-Fe-Co-P-CeO_2复合镀层。通过SEM、XRD、EDS等测试了复合镀层的表面形貌、截面形貌、物相结构和组成成分,同时,表征了复合镀层的硬度、耐磨和耐蚀性能,探究和分析了纳米稀土CeO_2颗粒浓度对镀层性能的影响。结果表明:该多元复合镀层为非晶态结构;随着镀液中CeO_2颗粒浓度的增加,复合镀层的显微硬度、耐磨性和耐蚀性均呈先增强后减弱的趋势;镀液中CeO_2颗粒浓度为1 g/L时,复合镀层的表面均匀致密,其HV_(0.1)显微硬度达到最大值5982 MPa,且具有最优的耐磨和耐蚀性能。     

Influence of heat treatment on surface morphology,hardness, wear and corrosion resistance of industrial phosphate coatings

Abstract

New phosphate black coatings for the improvement of mechanical properties on metallic objects have been developed to extend life time of machinery. The performance of phosphate black coatings was evaluated by weight gain studies, micro hardness studies, abrasive wear resistance and corrosion resistant measurement by electrochemical methods. The surface morphology of the coatings was assessed by XRD, SEM and XPS. The absorption coefficient of the coatings was evaluated by UV-visible spectrometer. Salt spray analysis was carried out to follow up the corrosion and get an idea about the performance of black coatings in automobile parts. The mechanical properties were very much improved after heat treatment of coatings at 200°C.     

Refinement of the primary Si particles in hypereutectic aluminum alloy

Al-Si alloys, with such excellent properties as low weight, low thermal expansion coefficient, and high wear-resistance, are ideal materials for the automobile and aerospace industries. However, their applications have been hampered by the coarsening of the primary-Si particles in Al-Si alloys. In this study, simple plastic deformation was used to reduce primary-Si particles and to improve the wear-resistance and mechanical strength of Al-Si alloys. Experimental results showed that mechanical rolling decreased the grain size of primary-Si particles in Al-Si alloys and reduced the variation in silicon particle size. After 60%-roll-reduction, the alloy showed an improved tensile strength of 340 MPa, which is attributed to the work hardening of the aluminum matrix and the dispersion strengthening of the primary-Si particles. Data from wear-resistance testing showed that rolling led to a reduction in wear loss. This improvement in wear resistance is due to the particle size refinement of silicon at a high percentage-roll-reduction.     

The effect of current mode and discharge type on the corrosion resistance of plasma electrolytic oxidation (PEO) coated magnesium alloy AJ62

Magnesium alloys are increasingly being used as lightweight materials in the automotive, defense, electronics, biomaterial and aerospace industries. However, their inherently poor corrosion and wear resistance have, so far, limited their application. Plasma electrolytic oxidation (PEO) in an environmentally friendly aluminates electrolyte has been used to produce oxide coatings with thicknesses of ~ 80 μm on an AJ62 magnesium alloy. Optical emission spectroscopy (OES) in the visible and near ultraviolet (NUV) band (285 nm–800 nm) was employed to characterize the PEO plasma. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the coated materials, and potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in a 3.5% NaCl solution were used to determine the corrosion behavior. It was found that the plasma discharge behavior significantly influenced the microstructure and the morphology of the oxide coatings and, hence the corrosion resistance. The corrosion resistance of the coated alloy was increased by changing the current mode from unipolar to bipolar, where the strong plasma discharges had been reduced or eliminated.     

轻合金表面工程技术述评

轻合金具有质量轻、比强度高、导热性好、抗电磁干扰等优异性能,被广泛应用于航空航天、汽车、摩托车、光学仪器、机械设备、医疗器械及电子产品等领域。但其还存在一些不足之处,诸如：硬度低、耐磨损性能差、耐腐蚀性能差等问题。因此,为了进一步提高合金的耐蚀性、耐磨性、抗微动磨损性、高温抗氧化性等,对其进行表面处理完全必要的。     

Abrasive wear resistance of electroless Ni-P coated aluminium after post treatment

Electroless nickel (EN) coatings are recognised for their hardness and wear resistance in automotive and aerospace industries. In this work, electroless Ni-P coatings were deposited on aluminium alloy substrate LM24 (Al-9 wt.% Si alloy) and the effect of post treatment on the wear resistance was studied. The post treatments included heat treatment and lapping with two different surface textures. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and micro-abrasion tester were used to analyse morphology, structure and abrasive wear resistance of the coatings. Post heat treatment significantly improved the coating density and structure, giving rise to enhanced hardness and wear resistance. Microhardness of electroless Ni-P coatings with thickness of about 15 μm increased due to the formation of Ni₃P after heat treatment.     

大气等离子喷涂FeCoCrNiAl高熵合金涂层的高温摩擦磨损性能

目的 研究环境温度对FeCoCrNiAl高熵合金涂层摩擦磨损性能的影响,探讨将其应用于高温及富氧环境中的可行性。方法 采用大气等离子喷涂制备FeCoCrNiAl高熵合金涂层,考察喷涂功率对涂层微观组织的影响;测试涂层的纳米力学性能,分析其对涂层摩擦磨损性能的影响;基于涂层及对偶磨球磨损表面形貌、元素分布及含量、物相组成,讨论涂层在室温及高温环境中的摩擦磨损特性与机制。结果 涂层中形成了白色、浅灰色、深灰色及黑色4种区域,区域颜色随O元素含量增加而加深,涂层纳米力学性能逐渐增加,进而将对其摩擦磨损性能造成影响。20 kW喷涂功率制备涂层的室温摩擦因数、磨损率及磨痕深度均达最佳值,分别为(0.70±0.02)、(9.22±0.01)×10^-5 mm³/(N·m)及(130±10)μm。室温环境下,磨粒磨损、疲劳磨损及塑性变形为涂层的主要磨损机制。20 kW功率制备涂层的摩擦因数、磨损率、磨痕深度等均随摩擦环境温度的升高先增加而后降低,经600℃摩擦试验后分别低至(0.58±0.01)、(6.14±0.01)×10^-5 mm<...     

Optimisation of the composition of KH20N45M3B welding wire

Summary

The main aim of this research is to investigate the suitability of ‘tailored blanks’, fabricated with laser welding technology, prior to forming. It is also a review of their fatigue and corrosion behaviour.

During the experiments, laser-welded joints were performed using different steel/thickness combinations, most commonly used in today's automobile industry. Joints were assessed by metallographic examination, as well as by pressing, fatigue and corrosion tests.

In order to evaluate the suitability of ‘tailored blank’ technology on an actual automotive component, a suspension mounting was produced by joining, using both laser and roller resistance welding, two FePO4 bare steel sheets of different thickness (1.5 and 2 mm).

Fatigue strength of the lighter component has generally produced comparable results to the standard component made in a single thickness (2 mm). This confirms the suitability of ‘tailored blank’ technology to save body weight and optimise material utilisation.     

SiCp/AZ91镁基复合材料的搅拌混合过程分析

镁基复合材料具有高的比强度、比刚度,较好的耐磨性、耐高温及减震性能,在航空、航天特别是汽车工业中具有潜在的应用前景。在制备颗粒增强镁基复合材料的各种方法中,搅拌熔铸工艺设备简单,成本低,最有希望实现大规模工业生产。在实验基础上建立了搅拌混合过程的动力学和热力学机制,制备了一种颗粒分布均匀的SiCp/AZ91镁基复合材料。     

形状记忆合金非常规加工综述(英文)

形状记忆合金(SMAs)由于具有多种特殊性能,如伪弹性、形状记忆效应、生物相容性、高的比强度、高耐蚀性、高耐磨性、良好的抗疲劳性能,成为不断发展的先进材料。因此,形状记忆合金被广泛应用于航空航天、医疗和汽车等方面。然而,由于严重的加工硬化和伪弹性,形状记忆合金的传统加工会造成严重的刀具磨损、费时以及低维畸变。这些材料可以使用非传统的方法,如激光加工、水射流加工(WJM)和电化学加工(ECM)进行机械加工,但这些方法受限于该材料的复杂性和力学性能。而电火花加工(EDM)和线切割(WEDM)能够很好的加工具有复杂形状和精密尺寸的形状记忆合金。介绍大量关于使用电火花和线切割加工形状记忆合金的研究,分析不同研究的差异,并展望未来的研究趋势。