HARDNESS PROPERTY AND WEAR RESISTANCE OF Al_2O_(3P)/ Zn-Al COMPOSITE

The hardness values and the wear resistance of Al2O3P/ Zn-Al composite, prepared by means of rheological casting technology,are investigated separately in this work. The results show that the addition of Al2O3P increases the hardness values of the matrix at both room and high temperature and improves the wear resistance of the material.The hardness values and the wear resistance of the composite rise with the increase of the particle volume fraction or the decrease of the particle size.The raising of test temperature results in a rapid descending of its hardness values.However, the addition of Al2O3P improves the property of high temperature resistance of Zn-Al alloys significantly.Moreover,the effect of quenching, tempering or cycling heat treatment on the hardness values of the composite is also studied.

Effects of Y_2O_3 on the microstructure and wear resistance of cobalt-based alloy coatings deposited by plasma transferred arc process

Cobalt-based alloys with different Y2O3 contents were deposited on Q235A-carbon steel using plasma transferred arc （PTA） welding machine. The effect of Y2O3 on the microstructure and wear resistance properties of the cobait-based alloys were investigated using an optical microscope, a scanning electron microscope （SEM）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. It was found that a cobalt-based solid solution with a face-centered cubic crystal structure was presented accompanied by the secondary phase M7C3 with a hexagonal crystal structure in the Y2O3-free cobalt-based alloy coating. Several stacking faults exist in the cobalt-based solid solution. The addition of Y2O3 leads to the existence of the Y2O3 phase in the Y2O3-modified coatings. Though stacking fault exists in the Y2O3-modified coatings, its density increases. The addition of Y2O3 can refine the microstructure and can increase the wear resistance properties when its contents are less than or equal to 0.8 wt.%. However, further increase of its contents will lead to the agglomeration of undissolved Y2O3 particles at the γ-Co grain boundary, and will lead to a coarse microstructure and lower wear resistance properties.

Fabrication of wear-resistant layers with lamellar eutectic structure by laser surface alloying using the in situ reaction between Cr and B_4C

To improve the wear resistance of Cr5 steel, wear-resistant layers with lamellar eutectic microstructure were fabricated by laser surface alloying（LSA）, which is dependent on the in situ reaction between Cr and B_4C. Our results indicated that the hypoeutectic structures of the LSA layers were divided into interdendritic eutectic structures and dendrites. The area fraction of the eutectic structures increased with increasing laser scanning speed, which improved the hardness and wear resistance of the LSA layers. The average hardness of the LSA layer prepared at a scanning speed of 8 mm/s was HV_（0.2） 883.9, which was 1.8 times greater than that of the traditional quenched layer（approximately HV 480）. After sliding for 659.4 m, the specimen prepared at a scanning speed of 8 mm/s exhibited a volume loss of 0.0323 mm^3, which was only 29.5% of the volume loss of the traditional quenched specimen.

Structure and wear resistance of TiN and TiAlN coatings on AZ91 alloy deposited by multi-arc ion plating

In order to investigate the microstructure of TiN and TiAlN coatings and their effect on the wear resistance of Mg alloy, TiN and TiAlN coatings were deposited on AZ91 magnesium alloy by multi-arc ion plating technology.TiN and Ti70Al30N coatings were prepared on the substrate,respectively,which exhibited dark golden color and compact microstructure.The microstructures of TiN and Ti70Al30N coatings were investigated by X-ray diffractometry(XRD)and scanning electron microscopy(SEM).The micro-hardness and wear resistance of TiN and Ti70Al30N coatings were investigated in comparison with the uncoated AZ91 alloy. The XRD peaks assigned to TiN and TiAlN phases are found.The hardness of TiN coatings is two times as high as that of AZ91 alloy, and Ti70Al30N coating exhibits the highest hardness.The wear resistance of the hard coatings increases obviously as result of their high hardness.

Improving wear resistance of magnesium by droplet spraying of Al-Si alloy

Abstract： In order to improve the surface hardness and wear resistance of magnesium, Al-13%Si （mass fraction） alloy coating was deposited on pure magnesium by droplet spraying process. The microstructure was studied by electron probe microanalysis and X-ray diffraction. The micro-hardness and wear resistance of coating were investigated in comparison with those of the substrate. It is found that the coating layer is composed of a-Al cellular due to rapid solidification. Formation mechanism of the coating is due to the obstruction of diffusion by in-situ formed Mg2Si in interracial layer. The coating exhibits higher hardness compared to that of the Mg substrate. As result of its high hardness, the wear resistance of the coating layer is about ten times that of the substrate. The droplet spraying process demonstrates that the magnesium surface can be strengthened by using the existing Al-Si alloys.

Wear resistance performance of high entropy alloy–ceramic coating composites synthesized via a novel combined process

Titanium nitride(TiN), characterized by its high hardness and strength, was widely used as ceramic coating to improve the wear resistance of matrix materials. In this work, AlCrFeNiTi_(x) high-entropy alloy(HEA) powders were synthesized by direct electrochemical reduction in molten salt from the mixed metal oxides. Then,TiN ceramic coating on the AlCrFeNiTi_x bulk HEA containing the topologically close-packed(TCP) phase(σphase, Laves phase, and Ti_(3)Al phase) was prepared by vacuum hot pressing sintering, where nitride element come from boron nitride parting agent sprayed on the graphite mold. The effect of titanium content on the crystal structure, microstructure, hardness, and wear resistance of the products were investigated by X-ray diffraction, field emission scanning electron microscope, field emission electron-probe microanalysis,Vickers hardness tester, and friction–abrasion testing machine. The bulk HEAs exhibit excellent hardness and its hardness increases significantly with the increase of titanium content. The wear mechanism changes from both of predominantly delamination and accompanied oxidative wear to single delamination wear,which is due to ultra-high melting point and high hot hardness of TiN, that can effectively prevent the oxidation and deformation of the worn surface. Formation of the ceramic coatings containing the TiN second phase and TCP phase are the key factor to AlCrFeNiTi_x alloy with the excellent hardness and wear properties.

Influence of Ta on Microstructure and Abrasive Wear Resistance of Laser Clad NiCrSiB Coating

A mixture of NiCrSiB alloy powder and tantalum （Ta） powder was used as laser clad material to improve abrasive wear resistance of the Ni-based coating. The microstructure and wear resistance of the coating were investigated. Addition of Ta element works to suppress the growth of coarse M7C3 carbide in the coating, resulting in a decrease in aspect ratio of coarse carbide. In the abrasive wear test, in situ synthesized TaC particles well bond with Ni-based matrix, and are hardly pull out from wear surface. Grooves on the worn surface of NiCrSiB coating are much deeper and sharper than those in the NiCrSiB＋Ta composite coating. Also, a weight loss of the composite coating is much lower than that of the NiCrSiB coating. The wear resistance of the laser clad Ni-based coating is enhanced to a much greater extent through the addition of Ta. This is attributed to the in situ synthesized hard TaC particles of nearly equiaxed shape, the Ni-based matrix strengthened by Ta and the decrease in aspect ratio of the coarse brittle carbides.

Double glow plasma carburization on zirconium to improve surface hardness and wear resistance

Though some important progress in the excel- lent mechanical properties of zirconium alloys have been reported, their high surface hardness and good wear prop- erties need to be explored further. In this work, a carbur- ized layer was formed on the surface of commercially pure zirconium by a double glow plasma hydrogen-free car- burizing technique. Commercial high-purity graphite was used as the carbon source material. X-ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dis- persive spectroscopy （EDS）, Vickers hardness test, friction and wear test were used to characterize the samples car- burized. The carburized layer could be clearly observed under a microscope. XRD patterns indicate that the zirco- nium carbide phase is formed in the carburized layer. The surface hardness of the sample increases significantly after carburization. Friction and wear tests results show that wear resistance and friction coefficient of zirconium are improved considerably after carburization. Surface plastic deformation is arrested to a low extent in contrast with pure zirconium because of the presence of ZrC phases during the wear test. The results may provide new insight into methods for surface strengthening of zirconium alloys.

Wear Resistance of Austenitic Steel Fe–17Mn–6Si–0.3C with High Silicon and High Manganese

To solve the problem of poor wear resistance in conventional Hadfield steels under medium and low stress, a new kind of steel with high silicon and high manganese Fe-17Mn-6Si-0.3C was designed and its wear resistance was studied. The results showed that it exhibited better wear resistance than conventional Hadfield steel in both dry friction and abrasive friction. The better wear resistance of the new steel with high silicon and high manganese resulted from the stressinduced γ→ε martensitic transformation.

Molybdenum alloying in cast iron and steel

Metal casting is an important manufacturing technology for efficiently producing massive components with complex shape.A large share of industrial castings is made from iron and steel alloys,combining attractive properties and low production cost.Upgrading of properties in cast iron and steel is mainly achieved by alloying and in fewer cases by heat treatment.Molybdenum is an important alloying element in that respect,increasing strength,hardness and toughness.It also facilitates particular heat treatments such as austempering.The paper describes the metallurgical functionality of molybdenum alloying in iron-based castings and demonstrates its effectiveness for applications in the automotive and mining industry.

New Mg_2Si based Alloy for Automobile Engine Cylinder Liner

New Mg2Si based alloy were prepared by mechanical alloying. Sintering temperature was from 825 to 865K, which indicated that few Mg2Si were produced at lower temperature while MgO were produced at higher temperature. Microstructure image showed that at sintering temperature of 855K, Mg2Si were mostly synthesized with the reaction of purity magnesia powder and silicon powder. Hardness and wear tests proved that the new synthetic silicon magnesium alloy had higher hardness and good wear resistance. Under the same testing conditions, it is found that the hardness of the new material is 420.50, and pure magnesium is only 41.65.In the same experiments it is also found that under the same pressure, pure magnesium alloys than silicon wearing capacity of pure magnesium is 2 times as high that of Mg2Si based alloy. It shows that Mg2Si based alloy is the ideal material for the wear parts of car engine cylinder liner because of its small density, stable dimension, high hardness and wear-resisting.

Wear Properties of Plasma Transferred Arc Fe-based Coatings Reinforced by Spherical WC Particles

Fe-based coatings reinforced by spherical WC particles were produced on the 304 stainless steel by plasma transferred arc(PTA) to enhance the surface wear properties. Three different Fe/WC composite powder mixtures containing 0 wt%, 30 wt%, and 60 wt% of WC were investigated. The microstructure and phase composition of the Fe/WC composite PTA coatings were evaluated systemically by using scanning electron microscope(SEM) and X-ray diffraction(XRD). The wear properties of the three fabricated PTA coatings were investigated on a BRUKER UMT TriboLab. The morphologies of the worn tracks and wear debris were characterized by using SEM and 3 D non-contract profiler. The experimental results reveal that the microhardness on the cross-section and the wear resistance of the fabricated coatings increase dramatically with the increasing adding WC contents. The coating containing 60 wt% of WC possesses excellent wear resistance validated by the lower coefficients of friction(COF), narrower and shallower wear tracks and smaller wear rate. In the pure Fe-based coating, the main wear mechanism is the combination of adhesion and oxidative wear. Adhesive and two-body abrasive wear are predominated in the coating containing 30 wt% of WC, whereas threebody abrasion wear mechanism is predominated in the coating containing 60 wt% of WC.

Influence of alloy ingredients on mechanical properties of ternary boride hard alloy clad materials

Using Mo, B-Fe alloy and Fe powders as raw materials, and adding C, Cr and Ni ingredients, respectively, or C, Cr and Ni mixed powders, ternary boride hard alloy clad materials was prepared on Q235 steel substrate by means of in-situ reaction and vacuum liquid phase sintering technology. The influence of alloy ingredients on the mechanical properties of ternary boride hard alloy clad materials was investigated. The results indicate that a mixture of 0.8% C, 5% Cr and 2% Ni ingredients gives a ternary boride hard alloy clad material with optimal mechanical properties, such as high transverse rupture strength, high hardness and good wear resistance.

Effect of deposition parameters on mechanical properties of TiN films coated on 2A12 aluminum alloys by arc ion plating (AIP)

TiN films were deposited on 2A12 aluminum alloy by arc ion plating (AIP). The Vickers hardness of the films deposited at different bias voltages and different nitrogen gas pressures, and that of the substrate were measured. The surface roughness of the TiN films diposited at –30 V and –80 V respectively and at different nitrogen gas pressure was measured also. The mass loss of TiN films deposited at 0 V, –30 V and –80 V respectively were analyzed in dry sand rubber wheel abrasive wear tests and wet ones in comparison with uncoated Al alloy and austenitic stainless steel (AISI 316L). It is revealed that the highest hardness of the TiN film is obtained at a bias voltage of –30 V and a N2 gas pressure of 0.5 Pa. The surface roughness of the film is larger at –80 V than that at –30 V and reduces as the increase of the N2 gas pressure. The mass loss of TiN-film coated 2A12 aluminum alloy is remarkably less than that of uncoated Al alloy and also that of AISI 316L, which indicates that the abrasive wear rate is greatly reduced by the application of TiN coating. TiN coating deposited by arc ion plating (AIP) technique on aluminum alloy can be a potential coating for machine parts requiring preciseness and lightness.

Shot lining of magnesium alloy with hard powders

To improve the surface properties,lining of magnesium alloys with hard powders by shot peening was carried out in order. The hard powders were tried to bond to the workpiece surface due to the collision of many shots.In order to fix the hard powders to the surface of the workpiece,the powders were set on an uneven surface.To easily facilitate fixing of powders,lining of the workpiece with the powder sandwiched between two aluminum foil sheets was also attempted.In this experiment,a centrifugal shot peening machine with an electrical heater was employed.The workpieces were magnesium alloys AZ31B and AZ91D,and the hard powders were commercial cemented carbide,alumina,and zirconia.The joinability of hard powders near the lined surface was observed by a optical microscope.The wear resistance was also evaluated by a wear test.The hard powders were successfully bonded to the surface of workpieces by the shot lining process.The results show that the present method is effective in wear resistance of the magnesium alloys.

The Stretch, Limit and Path Forward for Particle Reinforced Metal Matrix Composites of 7075 Al-Alloys

Al-based metal matrix composites [MMCs] have been the research interest of a wide spectrum of material scientists throughout the world for some over two decades now. The present paper has chosen one alloy system namely the 7xxx series and from an extensive literature review concluded that since the beginning of the new millennium nothing note worthy has been added to the knowledge already gained in the last quarter of the last century except confirm the earlier findings that MMCs if properly fabricated by choosing the processing route and with appropriate size and volume fraction of dispersoids can improve most of the mechanical, corrosion and wear resistant properties of the base alloy. The author’s own research activities using this alloy system for making MMCs that include attempts to improve upon the properties by making composites, ageing and also secondary processing have been included. An attempt has been made to establish the stretch to which improvement is possible in the alloy system by making composites and trying all other routes known for meaningful improvement in properties. Further, the way forward for such particulate composites has been drawn to realise the material scientists’ dream of seeing such MMCs as engineering components. For this, the areas which now need research include mass production of composites, focus on its machining, joining, processing as also reduction in the size of dispersoids are some of the areas that have been identified and discussed in the paper.

己二酸铵对铝合金硬质氧化膜性能的影响

选用2024铝合金作为基体,分别在不添加和添加己二酸铵的硫酸电解液中制备硬质氧化膜,并研究己二酸铵浓度对硬质氧化膜的微观形貌、化学成分、厚度、硬度、耐磨性能以及耐腐蚀性能的影响。结果表明:添加适量己二酸铵促进形成较致密的硬质氧化膜,并使硬质氧化膜增厚,硬度增大且耐磨性能和耐腐蚀性能明显提高。添加20 g/L己二酸铵制备的硬质氧化膜表面均匀性和致密性最好,厚度和硬度分别达到21.2μm、380.8 HV,摩擦系数和磨损失重仅为0.52和0.87 mg,并且腐蚀电流密度与铝合金基体相比降低了超过一个数量级,表现出更好的综合性能。但是添加己二酸铵并未改变硬质氧化膜的元素组成,所以硬质氧化膜的综合性能提高主要归因于添加适量己二酸铵参与了硬质氧化膜形成过程,并影响了铝离子传导过程,从而促使硬质氧化膜增厚且致密性改善。

建筑铝合金模板的表面改性与耐蚀耐磨性能研究

为了提升建筑铝合金模板的表面耐蚀性和耐磨性,在6061铝合金模板表面制备了聚氨酯/Al(Ni基非晶合金)涂层,研究了Ni基非晶合金粉替代Al粉比例对复合涂层表面形貌、截面形貌、硬度、耐磨性和耐蚀性的影响。结果表明:随着Ni基非晶合金粉替代率的升高,复合涂层表面孔洞数量减少,孔洞等缺陷所占面积分数有所减小,不同Ni基非晶合金粉体积分数的复合涂层的厚度都约为125μm。在涂层中加入Ni基非晶合金粉后,复合涂层的显微硬度、耐磨性有不同程度提高,与基体的结合强度有不同程度减小,且随着复合涂层中Ni基非晶合金粉体积分数的增加,复合涂层的显微硬度逐渐增大,与基体的结合强度和磨损率逐渐减小。添加Ni基非晶合金粉的复合涂层的腐蚀速率都小于未添加Ni基非晶合金粉的T0涂层,且Ni基非晶合金粉体积分数为45%的复合涂层具有较高的硬度、耐磨性及最佳耐蚀性能。

环片硬度对金基合金导电环摩擦磨损性能的影响

通过摩擦磨损试验、寿命试验和表界面分析方法研究了不同硬度的AuAgCu合金环片与AuNi合金刷丝在大气环境下的摩擦特性和磨损形貌特征.结果表明,随着导电环环片硬度由200.4 HV提高到243.6 HV,摩擦系数显著降低,环片磨痕宽度有所减小;环片与刷丝接触部位均存在典型的黏着磨损形貌特征,刷丝磨损区域形貌不规则,但硬环的磨损区域呈现出明显的犁削状划痕形貌;硬度不同的环片与刷丝对摩产生的磨屑均为薄片状且无团聚,磨屑成分与环片金属材料成分一致.此外,通过寿命试验前、后导电环环片和刷丝的质量分析可知,环片硬度的提高可显著降低导电环环片的磨损量.可见,在一定范围内提高导电环环片硬度,可以获得较好的减摩抗磨效果,为后续电接触材料对偶摩擦副的配副提供了试验和理论依据.

钢背及合金层厚度对ZChSnSb11-6巴氏合金耐磨性的影响

利用MFT-500多功能摩擦机对ZSnSb11Cu6(11-6)巴氏合金及采用离心铸造方法在40Cr钢钢背上浇铸的厚度为2.0、2.5 mm的ZChSnSb11-6巴氏合金层进行了摩擦磨损试验,研究了钢背及合金层厚度对巴氏合金耐磨性的影响。结果表明:与无钢背巴氏合金相比,有钢背2.5 mm厚巴氏合金的耐磨性提高了26.6%,而2.0 mm厚巴氏合金的耐磨性下降了12.8%。有钢背2.0 mm厚巴氏合金的硬度较高,磨痕和犁沟较浅,但其残余拉应力最大,麻点数量最多、剥落程度最大,耐磨性最差;而2.5 mm厚巴氏合金的麻点数量最少、剥落程度最小,磨痕和犁沟也较浅,耐磨性最好;相较于2.5 mm厚巴氏合金,无钢背巴氏合金的残余拉应力较小,但其硬度最低,磨痕和犁沟最深,麻点数量更多、剥落更严重,耐磨性较差。