铝合金等离子体基离子注入形成A1N／TiN层及其耐磨性能

用X射线光电子能谱（XPS）和小掠射角X射线衍射（GAXRD）研究了铝合金LY12等离子基离子注入形成A1N/TiN改性层的成分分布及相结构，在此基础上测量了改性层的纳米硬度，并进行了摩擦磨损试验，结果表明，氮和钛都有效地注入到铝合金里，后注入的元素对先注元素的分布和重要影响，钛，氮同时注入在试样表面形成一层稳定的钛，氧化合层，和未改性试样相经,形成的A1N/TiN改性层纳米硬度及承载能力都提高5倍以上，在低滑动载荷的增加，相应的耐磨性能有所降低，适当的改性层结构及其中分布的TiO2,TiN,TiAl3,Al2O3,AIN等相是性能改善的主要原因。     

铝合金等离子体基离子注入形成AlN/TiN层及其耐磨性能

用X射线光电子能谱 (XPS)和小掠射角X射线衍射 (GAXRD)研究了铝合金LY12等离子体基离子注入形成AlN/TiN改性层的成分分布及相结构 .在此基础上测量了改性层的纳米硬度 ,并进行了摩擦磨损试验 .结果表明 ,氮和钛都能有效地注入到铝合金里 ,后注入的元素对先注元素的含量和分布有重要影响 .钛、氮同时注入在试样表面形成一层稳定的钛、氮化合层 .和未改性试样相比 ,所形成的AlN/TiN改性层纳米硬度及承载能力都提高 5倍以上 .在低滑动载荷下 ,摩擦系数减小 70 %以上 ,耐磨性提高近 10倍 ,耐磨寿命提高了近 6倍 ,粘着磨损程度显著减轻 .随着载荷的增加 ,相应的耐磨性能有所降低 .适当的改性层结构及其中分布的TiO2 、TiN、TiAl3、Al2 O3、AlN等相是性能改善的主要原因     

Microstructure and Wear Resistance of in situ Formed Duplex Coating Fabricated by Plasma Nitriding Ti Coated 2024 Al Alloy

In this study, plasma nitriding was carried out on pure titanium film coated 2024 Al alloy to improve its surface mechanical property. Ti film with the thickness of 3.0 mm was firstly fabricated by means of magnetron sputtering method. Then, the Ti coated specimen was subjected to plasma atmosphere comprising 40% N2e60% H2 at 430 C for 8 h. The microstructures of the nitrided specimens were characterized by X-ray diffraction and scanning electron microscopy. Microhardness tester and pin-on-disc tribometer were used to test the mechanical properties of the untreated and nitrided specimen. The results showed that the surface of the nitrided specimen was composed of three layers（i.e. the outside nitride Ti N0.3layer, the middle Al3 Ti layer and the inside Al18Ti2Mg3 layer）. The surface hardness and wear resistance of 2024 Al alloy were increased simultaneously by duplex treatment. The untreated specimen exhibited severe adhesive wear while the nitrided one behaved in middle abrasive wear.     

铝合金等离子体基离子注入形成A1N/TiN层结构研究

用X射线光电子能谱和小掠射角X射线衍射研究了铝合金LY12等离子体基离子注入形成的AIN/TiN改性层的结构.结果表明,N和Ti能注入铝合金表面,N在注入层呈类高斯分布,而Ti沿注入方向呈梯度递减.后注入的Ti和N对先注入的N的含量和分布有重要影响.同时注入Ti和N,能在试样表面形成一层稳定的Ti,N层.所形成的AlN/TiN改性层主要由TiO2,TiN,TiAl3,Al2O3,AlN相组成.     

Tribological Behavior of Ti3SiC2—based Material

The wear and friction properties of Ti3SiC2-based materials were studied using the pin-on-disc method. The friction coefficient of Ti3SiC2-based material was not very sensitive to normal load, the steady state value, μ, increased from 0.4 to 0.5 when the normal load increased from 7.7 N to 14.7 N. The wear volume for Ti3SiC2 disc increased with increasing normal load or sliding distance in the tests. The average wear rate of Ti3SiC2-based material was 9.9×10-5 mm3/Nm. The debris on the Ti3SiC2 disc was essentially made up of Ti3SiC2 and steel pin materials, while the debris on the steel sliders was generally pin material. The wear mechanism was concluded as the fracture and delamination of Ti3SiC2-based materials followed by adhesive wear of steel sliders.     

Research on Modified Layers of Material Surface by Multi—Ion Beams

Multi-ion beams (MIB) is of material surface modification—a high technique based on ion implantment. The service life of a tool or die treated by MIB in site has increased by 2～4 times. The treated tool or die has obviosly higher hardness, lower friction coefficient and higher wear resistante. The modified layer is composed of (Ti_2N+TiN),(αFe+TiN) and (αFe(N)+Cr_7C_3) from surface to inside. The adhesion between the film and substrate is good, and the crystal partical of the layer is very fine like as nm size phase.     

Dry Sliding Tribological Properties of a Dendrite-reinforced Zr-based Bulk Metallic Glass Matrix Composite

In-situ dendrite-reinforced metallic glass matrix （MGM） composites with the composition of Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 were prepared with a vacuum arc melter by the copper mold suction casting. Effect of different normal loads and sliding velocities on the tribological properties of MGM composites was studied. The results showed that the friction coefficient and wear rate of composites initially descended with increasing the normal load and reached a minimum of 0.339 and 1.826 × 10^-4 mm^3/（N m） at 10 N, respectively, then ascended. Similarly, the friction coefficient and wear rate of composites initially decreased with the increase in the sliding velocity and reached a minimum of 0.330 and 2.389 × 10^-4 mm^3/（N m） at 0.4 m/s and 0.3 m/s, respectively, then raised. The wear mechanism of composites was mainly adhesive wear accompanied by abrasive wear at lower normal load and sliding velocity. However, the wear mechanism of composites was abrasive wear and adhesive wear as well as delamination at higher normal load and sliding velocity due to the nucleation and propagation of surface and subsurface cracks during the wear process. The flake-like and particle-like wear debris was the dominant shapes of debris observed.     

铝合金等离子体基离子注入形成AlN/TiN层结构研究

用X射线光电子能谱和小掠射角X射线衍射研究了铝合金LY12等离子体基离子注入形成的AlN/TiN改性层的结构。结果表明 ,N和Ti能注入铝合金表面 ,N在注入层呈类高斯分布 ,而Ti沿注入方向呈梯度递减。后注入的Ti和N对先注入的N的含量和分布有重要影响。同时注入Ti和N ,能在试样表面形成一层稳定的Ti,N层。所形成的AlN/TiN改性层主要由TiO2 ,TiN ,TiAl3 ,Al2 O3 ,AlN相组成     

Impurity Effect on Wear Resistance of Ultrafine-Grained Copper

The wear properties of ultrafine-grained(UFG) Cu samples of different purities were investigated in comparison with the coarse-grained(CG) Cu.The UFG Cu samples,prepared by means of plastic deformation via quasistatic compression,exhibit an enhanced wear resistance relative to the CG Cu samples.For both the UFG and the CG Cu samples,wear volumes increase at higher purities.A steady state worn subsurface structure was formed in each sample after sliding for 60 min,consisting of a heavily deformed nanostructured mixing layer(NML) on top of a continuous dynamic recrystallization(DRX) layer.A pronounced correlation is identified that wear volume increases monotonically with an increasing grain size of the DRX layer.The impurity level of the Cu samples has an obvious influence on the DRX grain sizes,which in turn determines the wear resistance of the Cu samples.     

Effect of Si3N4 Addition on the Mechanical Properties, Microstructures, and Wear Resistance of Ti-6Al-4V Alloy

In order to improve the wear resistance of Ti-6Al-4V, different amounts of Si3N4 powder were added into the alloy powder and sintered at 1250℃. Porous titanium alloy with higher wear resistance was successfully fabricated. At sintering temperature, reaction took place and a new hard phase of Ti5Si3 formed. The mechanical properties of the fabricated alloys with different amounts of Si3N4 addition were investigated. The hardness of Ti-6Al-4V, which is the index of wear resistance, was increased by the addition of Si3N4. Amounts of Si3N4 addition have very significant influences on hardness and compressive strength. In present study,titanium alloy with 5 wt pct Si3N4 addition has 62% microhardness and 45% overall bulk hardness increase,respectively. In contrast, it has a 16.4% strength reduction. Wear resistance was evaluated by the weight loss during wear test. A new phase of Ti5Si3 was detected by electron probe microanalyzer （EPMA） and X-ray diffraction （XRD） method. The original Si3N4 decomposed during sintering and transformed into titanium silicide. Porous structure was achieved due to the sintering reaction.     

Effects of Yttrium Addition on Microstructure, Hardness and Resistance to Wear and Corrosive Wear of TiNi Alloy

TiNi alloy has a high resistance to wear and could be an excellent candidate for various tribological applications. In this paper, it was demonstrated that by addition of yttrium, hardness properties and resistance to wear and corrosive wear of TiNi alloy were improved. New yttrium rich regions were formed in microstructure of TiNi alloy. The improved properties of this alloy by the yttrium addition could be attributed to the formation of these regions. The results showed that there was an optimum content for addition of yttrium between 2% and 5% (in wt%), and above this content the improvement in properties of TiNi became minor.     

Evaluation the Properties of Titanium Matrix Composites by Melting Route Synthesis

The main purpose of this study is an in-situ synthesis of （TiB＋TiC） hybrid titanium matrix composites （TMCs） by vacuum induction melting method and to verify its mechanical properties.The melting route was adopted to synthesize the commercial pure titanium （cp Ti） and granular boron carbide （B-4C）.The reinforcements,the fraction of 10 vol.pct,were formed by adding 1.88 wt pct B-4C to cp Ti.After in-situ synthesis of TMCs,electron probe micro-analysis elemental mapping was carried out to confirm the distribution and shape of reinforcements.The cone-on-disk type sliding wear test was also done for the identification of TMCs.It is concluded that （TiB＋TiC） hybrid TMCs can be in-situ synthesized and has better wear properties than H13.     

Effect of environments and normal loads on tribological properties of nitrided Ni_(45)(FeCoCr)_(40)(AlTi)_(15) high-entropy alloys

The tribological properties of nitrided Ni_(45)(FeCoCr)_(40)(AlTi)_(15) high-entropy alloys(HEAs) were investigated in air and simulated acid rain under different normal loads(5,7,10,and 12 N) at ambient temperature.The results revealed that as-cast HEAs were only composed of FCC phase,while the volume fraction of FCC phase in the nitrided alloys was significantly reduced.Moreover,the hard phases of AIN,CrN,Fe4 N,and TiN phases were formed in the nitrided alloys.The thickness of the nitriding layer was about 8.4 μm.The hardness increased from 8.7 GPa in as-cast alloys to 14.5 GPa in the nitrided alloys.In addition,under the same conditions,the friction coefficient of the nitrided alloys was higher than that of as-cast alloys,but the wear rate was generally lower than that of as-cast alloys.Furthermore,the wear rate of the nitrided alloys was the lowest in acid rain due to the lubrication,cleaning,and cooling in the liquid environment.In air,dominating wear mechanisms in as-cast and nitrided alloys were abrasive,delamination,and adhesive wears.And,the wear mechanism of as-cast and nitrided alloys in acid rain was mainly abrasive and corrosion wears.     

铝合金等离子体基离子注入形成AlN／TiN层结构研究

用X射线光电子能谱和小掠射角X射线衍射研究了铝合金LY12等离子体基离子注入形成的AlN/TiN改性层的结构。结果表明,N和Ti能注入铝合金表面,N在注入层呈类高斯分布,而Ti沿注入方向呈梯度递减。后注入的Ti和N对先注入的N的含量和分布有重要影响。同时注入Ti和N,能在试样表面形成一层稳定的Ti,N层。所形成的AlN/TiN改性层主要由TiO2,TiN,TiAl3,Al2O3,AlN相组成。     

A Study on the Wear Behaviour of Dual Phase Steels

Dual phase （DP） steels containing four different amounts of martensite ranging from 43 vol. pct to 81 vol. pct have been developed from 0.2 wt pct carbon steel by intercritical heat treatment at a fixed temperature of 780℃ with varying holding times followed by water quenching. Dry sliding wear tests have been conducted on DP steels using a pin- on-disk machine under different normal loads of 61.3, 68.5, 75.7 and 82.6 N and at a constant sliding speed of 1.20 m/s. At these loads, the mechanism of wear is primarily delamination, which has been confirmed by SEM micrographs of subsurface and wear debris of samples. Wear properties have been found to improve with the increase in martensite volume fraction in dual phase steels.     

Combined Effect of Aluminum Content and Layer Structure on the Oxidation Performance of Ti1-xAlxN Based Coatings

TiN,Ti1-xAIxN single layer coatings and TiN/Ti1-xAIxN multilayer coatings were deposited on SKH51 tool steel substrate by arc ion plating.The coatings were annealed in air to study the effect of aluminum and film structure on the oxidation performance.The surface morphology and structure were characterized by scanning electron microscopy and X-ray diffraction.The element distribution on the cross section was analyzed by electron probe microscopy.It is found that the oxidation resistance of these Ti1-xAlxN based coatings is mainly attributed to aluminum content in them.In comparison with the Ti1-xAlxN single layer coating,the TiN layer inserting into the Ti1-xAlxN in a multilayer coating increases the tendency of Ti diffusion toward the surface and forms a Ti-enriched top surface oxide layer,thus degrades the oxidation resistance.As far as the oxidation resistance is concerned in this study,Ti0.33Al0.67N single layer coating performs the best among all coatings.The kinetic of oxidation behavior of all coatings presents two definite stages.One is a slow oxidation growth which conforms to parabolic law,and the other presents severe mass gain with oxidation duration.The annealing time for severe oxidation initiation is responsible to Fe2O3formation in the oxide scale.     

Effect of Ringer's Solution on Wear and Friction of Stainless Steel 316L after Plasma Electrolytic Nitrocarburising at Low Voltages

A plasma electrolytic nitrocarburising(PEN/C) process was performed on stainless steel 316L to improve the surface properties for using as medical implants.A bath was optimised to reduce the required voltage to 150 volts.Aqueous urea-based solutions with 10% NH 4 Cl were prepared with slightly different amounts of Na 2 CO 3 to optimise the electrolyte composition.The surface and the cross-section morphologies were studied by scanning electron microscopy.The microstructure and the chemical composition of samples were investigated by X-ray diffraction(XRD) and energy dispersive X-ray(EDX) techniques.The microstructure of the outer layer of the coatings was found to be a complex oxide containing Cr and Fe.The wear properties of the samples were examined by using a pin on disk wear test with Ringer s solution and were compared with their wear properties in the ambient atmosphere.The Ringer s solution acted as a lubricant,reducing friction coefficient.Hardness and roughness were also studied.The bath with the composition of 10% NH 4 Cl and 3% Na 2 CO 3 exhibited the best tribological properties.The results showed that the tribological properties of treated samples were improved and the wear mechanism was abrasion of the pin.     

In situ selective laser gas nitriding for composite TiN/Ti-6Al-4V fabrication via laser powder bed fusion

Laser-assisted gas nitriding of selective Ti-6Al-4V surfaces has been achieved during laser powder bed fusion fabrication by exchanging the argon build gas environment with nitrogen. Systematic variation of processing parameters allowed microdendritic Ti N surface coatings to be formed having thicknesses ranging from a few tens of microns to several hundred microns, with TiN dendrite microstructure volume fractions ranging from 0.6 to 0.75; and corresponding Vickers microindentation hardness values ranging from ～7.5 GPa–9.5 GPa. Embedded TiN hard layers ranging from 50 μm to 150 μm thick were also fabricated in the laser-beam additively manufactured Ti-6Al-4V alloy producing prototype, hybrid, planar composites having alternating, ductile Ti-6Al-4V layers with a hardness of ～4.5 GPa and a stiff, TiN layer with a hardness of ～8.5 GPa. The results demonstrate prospects for fabricating novel, additively manufactured components having selective, hard, wear and corrosion resistant coatings along with periodic,planar or complex metal matrix composite regimes exhibiting superior toughness and related mechanical properties.     

Wear behavior of light-weight and high strength Fe-Mn-Ni-Al matrix self-lubricating steels

The good combination of mechanical and tribological properties for self-lubricating materials is crucial. In this work, novel self-lubricating Fe-16.4 Mn-4.8 Ni-9.9 Al-xC(wt%) steels containing graphite phase were fabricated using mechanical alloying and spark plasma sintering. The compositions of the steels were designed by using thermodynamic calculation, and the effect of carbon addition on the microstructure was further investigated. The steel possesses high hardness of 621 HV, high yield strength of 1437 MPa and good fracture toughness at room temperature. The yield strengths are still above 600 MPa at 600?C.The tribological behavior and mechanical properties from room temperature to 800?C were studied, and the wear mechanisms at elevated temperatures were discussed. The steel has a stable friction coefficient of 0.4 and wear rate in a magnitude of 10~(-6) mm~3/N·m below 600?C. The good tribological properties of the steels were mainly attributed to the high hardness, lubrication of graphite and stable surface oxide layer.     

Friction and Wear Behaviors of Nanostructured Metals

Nanostructured （ns） materials, i.e., polycrystalline materials with grain sizes in the nanometer regime （typically below 100 nm）, have drawn considerable attention in the past decades due to their unique properties such as high strength and hardness. Wear resistance of ns materials, one of the most important properties for engineering materials, has been extensively investigated in the past decades. Obvious differences have been identified in friction and wear behaviors Between the ns materials and their corresponding coarse-grained （cg） counterparts, consistently correlating with their unique structure characteristics and mechanical properties. On the other hand, the superior tribological properties of ns materials illustrate their potential applications under contact loads. The present overview will summarize the important progresses achieved on friction and wear behaviors of ns metallic materials, including ultrafine-grained （ufg） materials in recent years. Tribological properties and effects on friction and wear behaviors of ns materials will be discussed under different wear conditions including abrasive wear, sliding wear, and fretting wear. Their correlations with mechanical properties will be analyzed. Perspectives on development of this field will be highlighted as well.