Zhong HAN
,
Yusheng ZHANG
材料科学技术（英文）
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.
关键词:
Nanostructured metals
,
metals
,
Friction
,
Wear
,
Mech
Ruihua HU
,
Montasser M.Dewidar
,
Hyo-Jin KIM
,
Jae-Kyoo LIM
,
null
材料科学技术（英文）
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.
关键词:
Ti-6Al-4V
,
alloy
,
Wear
,
Sintering
,
reaction
Jiqiang MA
金属学报(英文版)
An ultrafine grained Fe-40Al intermetallic compound is fabricated by a self-propagating high temperature synthesis (SHS) casting. The XRD result shows that the Fe-40Al intermetallic compound consists of the B2 FeAl phase. The Fe-40Al intermetallic compound presents ultrafine grain size in the range of 100--600~nm, leading from the high nucleation rate and the low growth rate. The Fe-40Al intermetallic compound exhibits high hardness (3.4 GPa) and high bending strength (830 MPa) and high compressive strength (2700 MPa), which originate from the ultrafine-structure in the material. The effect of the load on dry-sliding wear rate of the material against AISI52100 steel was investigated. The wear rate increases with the increase of normal load. The dominated wear mechanism is microfracture.
关键词:
Iron aluminides
,
Self-propagating high temperature synthesis (SHS) casting
,
Ultrafine grain
,
Preparation
,
Wear
Jihui WANG
,
E.Wieers
,
L.M.Stals
,
J.P.Celis
材料科学技术（英文）
MoSx coatings were prepared by bipolar-pulse DC unbalanced magnetron-sputtering system with the variation of coating thickness at different Ar pressures. The composition and surface morphology were determined by using energy dispersive X-ray and scanning electron microscopy; the structural characterisation was analyzed by X-ray diffraction. The friction and wear properties were investigated by fretting tests in air with less than 10% and 50% relative humidity.At 0.40 Pa pressure, (002) basal plane orientation was formed throughout the coatings. At 0.88 Pa and 1.60 Pa pressures, (002) basal plane orientation was only noticed in the first stage of coating growth (around 0.20 µm in thickness), and then edge orientations with their basal planes perpendicular to the surface would be evolved in the coatings. Humidity has a minor influence on the coatings that have (002) basal plane orientation, whereas the tribological properties of MoSx coatings with edge orientations are greatly affected by humidity. The mechanisms of coating growth and friction and wear processes are discussed.
关键词:
MoSx coating
,
null
,
null
,
null
Kaijin HUANG
材料科学技术（英文）
The microstructure and wear behaviour of the thermite reaction coating produced by the hybrid laser cladding-remelting on AA7075 aluminum alloy for the systems of Al-CuO-SiO2, Al-Cr2O3-SiO2, Al-Fe2O3-SiO2, and Al-TiO2-SiO2 were studied. The results of the X-ray diffraction (XRD) analysis show that in all the four reaction coatings, α-Al2O3 and γ-Al2O3 phases were present at the top surface, together with various intermetallic phases, the corresponding reduced metal and Al phase in the fusion zone. Under the dry sliding condition, the wear resistance, in terms of weight loss, of the laser-clad specimens was considerably higher than that of the untreated specimen. The predominant wear mechanism of the former specimens was abrasive wear, while for the latter, it was the adhesive wear that prevailed.
关键词:
Laser cladding
,
cladding
,
thermite
,
reaction
,
aluminu
Mustafa BOZ
,
Adem KURT
材料科学技术（英文）
Friction-wear properties of the ZrSiO4 reinforced samples were measured and compared with those of plain bronze based ones. For this purpose, density, hardness, friction coefficient wear behaviour of the samples were tested. Microstructures of samples before and after sintering and worn surfaces were also investigated by scanning electron microscopy (SEM), and the wear types were determined. The optimum friction-wear behaviour was obtained in the sample compacted at 500 MPa and sintered at 820oC. Density of the final samples decreased with increasing the amount of reinforcing elements (ZrSiO4) before pre-sintering. However after sintering, there is no change in density of the samples including reinforcing elements (ZrSiO4). With increasing friction surface temperature, a reduction in the friction coefficient of the samples was observed. However, the highest reductions in the friction coefficients were observed in the as-received samples containing 0, 5% reinforced ZrSiO4. The SEM images of the sample indicated that while bronze-based break lining material without ZrSiO4showed abrasive wear behaviour, increasing the amount of ZrSiO4resulted a change in abrasive to adhesive wear mechanism. All samples exhibited friction-wear values, which were within the values shown in SAE-J661 standard. With increasing the amount of reinforcing ZrSiO4, wear resistance of the samples was increased. However samples reinforced with 5% and 6% ZrSiO4showed the best results.
关键词:
Friction materials
,
null
,
null
,
null
,
null
Nairong TAO
,
Weiping TONG
,
Zhenbo WANG
,
Wei WANG
,
Manling SUI
,
Jian LV
,
Ke LU
材料科学技术（英文）
A porosity-free and contamination-free surface layer with grain sizes ranging from nanometer to micrometer in Fe samples was obtained by surface mechanical attrition treatment (SMAT) technique. Mechanical and wear properties of the surface layer in the SMATed and annealed Fe samples were measured by means of nanoindentation and nanoscratch tests, respectively. Experimental results showed that the hardness of the surface layer in the SMATed Fe sample increased evidently due to the grain refinement. The elastic moduli of the surface layers in the SMATed and annealed Fe samples were unchanged, independent of grain size in the present grain size regime. Compared with the original Fe sample, the wear resistance enhanced and the coefficient of friction decreased in the surface layer of the SMATed Fe sample.
关键词:
Nanocrystallites
,
null
,
null
,
null
,
null
A.Wiengmoon
,
T.Chairuangsri
,
N.Chomsang
,
N.Poolthong
,
J.T.H.Pearce
材料科学技术（英文）
Effects of heat treatments on hardness and dry wear properties of a semi-solid processed Fe-26.96 wt pct Cr-2.91 wt pct C cast iron were studied. Heat treatments included tempering at 500℃, destabilisation at 1075℃ and destabilisation at 1075℃ plus tempering at 500℃, all followed by air cooling. Electron microscopy revealed that, in the as-cast condition, the primary proeutectic austenite was round in shape while the eutectic M7C3 carbide was found as radiating clusters mixed with directional clusters. Tempering did not change the microstructure significantly when observed by scanning or transmission electron microscopy. Destabilisation followed by air cooling led to a precipitation of secondary M23C6 carbide and a transformation of the primary austenite to martensite. Precipitation behaviour is comparable to that observed in the conventionally cast iron. Tempering after destabilisation resulted in a higher amount of secondary carbide precipitation within the tempered martensite in the eutectic structure. Vickers macrohardness and microhardness in the proeutectic zones were measured. Dry wear properties were tested by using a pin-on-disc method. The maximum hardness and the lowest dry wear rate were obtained from the destabilisation-plus-tempering heat treatment due to the precipitation of secondary carbides within the martensite matrix and a possible reduction in the retained austenite.
关键词:
Semi-solid process
,
null
,
null
,
null
,
null
Bong-Jae Choi
,
Si-Young Sung
,
Myoung-Gyun Kim
,
Young-Jig Kim
材料科学技术（英文）
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 (B4C). The reinforcements, the fraction of 10 vol. pct, were formed by adding 1.88 wt pct B4C 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.
关键词:
Titanium matrix composites
,
null
,
null
,
null
杨洋
,
何国球
,
卢棋
,
刘兵
,
朱旻昊
上海金属
通过柱面对柱面的接触方式,研究了35CrMoA钢在圆形路径载荷下的微动疲劳失效特性,采用扫描电子显微镜对微动疲劳试样的微动斑、磨削及微裂纹进行观察.试验结果表明:随着微动摩擦磨损的进行,磨损方式逐渐由粘着磨损转变为磨削磨损;微动斑的粘着区存在着圆形或近圆形的微小斑痕,滑移区上堆积了大量的磨屑;微动疲劳失效部位发生在粘着区与滑移区的交界处,并由于等效应力的不同而失效位置不同;微动疲劳的微裂纹存在于晶界上,并且沿晶界扩展.
关键词:
35CrMoA钢
,
微动疲劳
,
圆形路径
,
摩擦磨损
,
多轴
