Dry Friction and Wear Characteristics of Rare-Earth／MoSiz Composite

The dry friction and wear characteristics of rare earth/MoSi2 composite against 45 steel under different loads were investigated by using an M-200 type friction and wear tester. SEM and XRD were used to analyze the morphology of the friction surface and the phase of worn piece in order to reveal the wear mechanism of rare-earth/MoSi2 composite. Results show that the relationships of friction coefficient, μ, or wear rate, W, of MoSi2 and RE/MoSi2 composite to loads,p, can be fitted well with the following function: μ (or W) = a bp cp2 dp3 ep4, where a, b, c, d and e are fitting constants depending on materials and confidence. MoSi2 and rare-earth/MoSi2 composite have excellent wear resis-tance. When load is in the range of 80 - 120 N, the wear rate of RE/MoSi2 composite is lower than that of MoSi2 materialby about 65 %. The main wear mechanism of rare-earth/MoSi2 composite is adhesive wear.     

Friction and Wear Characteristics of Mg-Al Alloy Containing Rare Earths

The influence of rare earth on the friction and wear characteristics of magnesium alloy AZ91 and AM60 were studied. The results show that the wear resistance properties of rare earth magnesium alloys are better than those of matrix alloy under the testing conditions. The anti-wear behaviour of AZ91 alloy is much better than that of AM60 alloy. In dry sliding pmcess, magnesium alloys undergo a transition from mild wear to severe wear. The addition of rare earths refine the structure of alloys, improve the comprehensive behaviors of magnesium alloys,increase the stability of oxidation films on worn surfaces,enhance the loading ability of rare earth magnesium alloys,and delay the transition from mild wear to sevre wear effectively.     

Dry Sliding Oxidative Wear in Plain Carbon Dual Phase Steel

 To investigate the tribological potential of the dual phase (DP) steel as a wear resistant material, the wear and the friction characteristics of this steel, which consists of hard martensite islands embedded in a ductile ferrite matrix, have been investigated and compared with those observed in plain carbon hardened (H) steel that has the same carbon content of 02%. Dry sliding wear tests have been carried out using a pin on disk wear testing machine at different normal loads of 213 N, 285 N, 357 N, and 426 N and at a constant sliding velocity of 120 m/s. The analysis of surface and wear debris of samples showed that the wear mechanism was mainly mild oxidative. The friction and the wear rate of the H steel and the DP steel have been explained with respect to the microstructure and the wear mechanism.     

Development of New WearResistant Surface Coating at Elevated Temperature

Because of good oxidation resistance at high temperature and excellent mechanical properties of Ni3Al and high hot hardness, and good oxidation resistance of chromium carbide, chromium carbide particle reinforced Ni3Al matrix composite would possess excellent wear resistance at elevated temperature. Cr3C2NiAlNi welding wire was produced by pressureless sintering process in vacuum. When the welding wire was welded on the surface of carbon steel, under the action of the physical heat of arc, NiAl reacted with nickel to form Ni3Al and carbide particle reinforced Ni3Al matrix composite was formed on the welding layers. Cr3C2 was dissolved during welding and dispersed Cr7C3 was formed, which strengthened the Ni3Al matrix significantly. The Cr7C3Ni3Al interface was broadened, and a zone of interdiffusion and a new phase M23C6 were formed, indicating that a good bond has been formed. The hardness of Cr7C3/Ni3Al composite at room and elevated temperatures is much higher than that of stellite alloys. In addition, Cr7C3/Ni3Al composite possesses better high temperature oxidation resistance than stellite 12 alloy. So Cr7C3/ Ni3Al composite can become an attractive potential candidate for elevated temperature wearresistant surface material.     

The Wear Behavior of In-Situ Al–AlN Metal Matrix Composites

Al–AlN composites are synthesized using NH₄Cl + CaO powder as a nitrogenation precursor in the melt of pure aluminum. In-situ formation of AlN to varying volume fraction is attempted using different proportion of NH₄Cl + CaO precursor into the aluminum melt held at 700 °C. Mechanical properties of synthesized metal matrix composites are evaluated for different volume fraction and distribution of AlN particles in aluminum matrix. Agglomeration of AlN is noticed with increasing precursor addition and synthesis time into the aluminum matrix. Due to heterogeneous distribution of AlN particles in aluminum matrix, marginal changes in hardness are observed. Pin on disc, dry sliding wear of metal matrix composites is carried to study wear behavior of synthesized composites. Composite with good dispersion of AlN particulates has shown higher hardness and wear resistance. Present paper discusses wear behavior of composites with different weight fraction of AlN tested under load and sliding distance as wear parameters. The shearing mechanism of agglomerate due to friction and its correlation with the wear loss is also highlighted in the present paper.     

Dry Friction and Wear Characteristics of Rare-Earth/MoSi_2 Composite

MolybdenumDisilicide (MoSi2 )intermetallicspossessesmetallic likeandceramic likeproperties .Studyonitsfrictionandwearcharacteristicshasim portanttheoreticalandpracticalsignificance[1～ 5] .ItisusefultoreinforcetheMoSi2 materialbyusingthesec ondphaseforimprovementofthefrictionandwearcharacteristics[3 ,6] .Hawketal.[3 ] comparedthewearresistanceofMoSi2 withthatofMoSi2 Nbcomposites ,Nb ,aluminides (Fe3 Al,TiAl)andoxidationceramics(Al2 O3 andPS ZrO2 ) ,andfoundthatthewearresis tanceofMoS…     

Wear Mechanisms of High Chromium Iron Roll under Hot Rolling Conditions

ＷｅａｒＭｅｃｈａｎｉｓｍｓｏｆＨｉｇｈＣｈｒｏｍｉｕｍＩｒｏｎＲｏｌｕｎｄｅｒＨｏｔＲｏｌｉｎｇＣｏｎｄｉｔｉｏｎｓＣｕｉＰｅｉｙｏｎｇ①ＡＢＳＴＲＡＣＴＢｙｕｓｉｎｇａｒｅｆｏｒｍｅｄｌａｂｏｒａｔｏｒｙｒｏｌｉｎｇｍｉｌ，ｈｏｔｗｅａｒｔｅｓｔ...     

Structure and Wear Resistance of Plasma-Sprayed NiCrBSiC–TiCrC Composite Powder Coatings

Powder Metallurgy and Metal Ceramics - The NTC20 and NTC40 composite powders were produced by conglomeration from the NiCrBSiC self-fluxing alloy with additions of 20 and 40 wt.% TiCrC,...     

Improving Wear Resistance of the Ni-base Thermal Spray-Welding Coating Using Rare Earths

ＩｍｐｒｏｖｉｎｇＷｅａｒＲｅｓｉｓｔａｎｃｅｏｆｔｈｅＮｉｂａｓｅＴｈｅｒｍａｌＳｐｒａｙＷｅｌｄｉｎｇＣｏａｔｉｎｇＵｓｉｎｇＲａｒｅＥａｒｔｈｓＺｈａｉＧｕａｎｇｊｉｅ（翟光杰）（ＩｎｓｔｉｔｕｔｅｏｆＰｈｙｓｉｃｓ，ＡｃａｄｅｍｉｃａＳｉ...     

Effect of Alloying Elements on Thermal Wear of Cast Hot-Forging Die Steels

The effect of main alloying elements on thermal wear of cast hot-forging die steels was studied. The wear mechanism was discussed. The results show that alloying elements have significant influences on the thermal wear of cast hot-forging die steels. The wear rates decrease with an increase in chromium content from 3% to 4% and molybdenum content from 2% to 3%, respectively. With further increase of chromium and molybdenum contents, chromium slightly reduces the wear resistance and molybdenum severely deteriorates the wear resistance with high wear rate. Lower vanadium/carbon ratio （1.5-2.5） leads to a lower wear resistance with higher wear rate. With an increase in vanadium/carbon ratio, the wear resistance of the cast steel substantially increases. When vanadium/carbon ratio is 3, the wear rate reaches the lowest value. The predominant mechanism of thermal wear of cast hot-forging die steels are oxidation wear and fatigue delamination. The Fe2O3 and Fe3O4 or lumps of brittle wear debris are formed on the wear surface.     

Mechanical Properties and Friction／Wear Behavior of Copper Alloyed Powder Composites

Copper alloyed powder composites containing nanoparticles were developed by hot pressing. Effects of nanoscale activated sintering aid and fine ceramic particles Al2O3 on hardness, working quality, and behaviors of friction and wear of the composites have been studied, compared with the composites including mieroscale activated sintering aid and microscale ceramic particles. The microstructures of the samples were analyzed by SEM. The resuits show that the materials with nanoscale sintering aid and fine ceramic particles have better mechanical properties and abrasive resistance than the materials with microscale activated sintering aid and microceramic particles. Moreover, element mutual transfer occurs between samples (strip) and abrasive wheel (ring).     

Effect of Rare Earth Elements on the Impact Wear Resistance of Nitrocarburizing Layers

In this paper the effect of rare earth elements on the toughness and impact wear resistance of nitrocarburiz-ing layers is studied.The experimental results show that the toughness and impact wear resistance ofRE-nitrocarburizing layers are increased significantly compared with that of conventional nitrocarburizing lay-ers.The service life of hot die for manufacturing bicycle bolts increased more than 100%.The impact wearmechanism of RE-nitrocarburizing layers is investigated by SEM as well.     

Friction Surfaces and Wear Products of Sn–Sb–Cu-Based Composite Materials

The structure and the tribological properties of the composite materials based on an Sn–Sb–Cu alloy (B83 babbit) and fabricated by hot pressing of powders are studied under dry sliding friction conditions. Modified schungite and silicon carbide are chosen as reinforcing materials. The composite material fabricated by a powder technology and reinforced by silicon carbide and modified schungite particles is found to have the doubled wear resistance as compared to a cast B83 alloy at a comparable friction coefficient.     

Alloying Design for High WearResistant Cast HotForging Die Steels

The alloying design of cast hotforging die steels was analyzed. The relationship of the life of cast hotforging dies with the failure patterns was studied. The thermal wear resistance was believed to be the key property for the alloying design of cast hotforging die steels. The alloying design parameters were selected and optimized for the cast hotforging die steel with high wear resistance. The wear resistance of the optimized cast die steel was evaluated in comparison with commercial H13 steels and 3Cr2W8V steel. In the new cast hotforging die steel, VC is predominant carbide with Cr and Mo as the main solution elements in αFe. It is found that the cast die steel has significantly lower wear rate than normal H13 steel and 3Cr2W8V steel, almost the same as that of high purity H13 steel. The high wear resistance of the new cast hotforging die steel can be attributed to its reasonable alloying design and nonsensibility to the detrimental function of S and P.     

Microstructure and Wear Resistance of Laser Clad Cobalt-Based Alloy／SiCp Composite Coating

The SiCp (20%) reinforced cobalt-based alloy composite coatings deposited by lasercladding on IF steel were introduced. The microstructure across the whole section of such coat-ings was examined using optical microscope, scanning electron microscope (SEM) and X-raydiffractometer (XRD), and the wear resistance of the coatings was measured by MM-200 typewear testing machine. The results show that the SiCp is completely dissolved during laser clad-ding and the primary phase in the coatings is r-Co. The other phases, such as SizW, CoWSi,Cr3Si and CoSi2, are formed by carbon, silicon reacting with other elements existing in themelting pool. There are various crystallization morphologies in different zones, such as planarcrystallization at the interface, followed by cellular and dendrite crystallization from interface tothe surface. The direction of solidification changes from one direction perpendicular to interfaceto multi-directions at the central and upper regions of the clad. The wear resistance of the cladis improved by adding SiCp.     

Effect of Alloying Elements on Thermal Wear of Cast HotForging Die Steels

The effect of main alloying elements on thermal wear of cast hotforging die steels was studied. The wear mechanism was discussed. The results show that alloying elements have significant influences on the thermal wear of cast hotforging die steels. The wear rates decrease with an increase in chromium content from 3% to 4% and molybdenum content from 2% to 3%, respectively. With further increase of chromium and molybdenum contents, chromium slightly reduces the wear resistance and molybdenum severely deteriorates the wear resistance with high wear rate. Lower vanadium/carbon ratio (15-25) leads to a lower wear resistance with higher wear rate. With an increase in vanadium/carbon ratio, the wear resistance of the cast steel substantially increases. When vanadium/carbon ratio is 3, the wear rate reaches the lowest value. The predominant mechanism of thermal wear of cast hotforging die steels are oxidation wear and fatigue delamination. The Fe2O3 and Fe3O4 or lumps of brittle wear debris are formed on the wear surface.     

Investigation on the Wear Properties of Primary Si Modified Al–20Si Alloy

In the present study, Al?C20Si alloy has been modified by Cu?C13P master alloy to obtain Al?C20Si?C0.1P alloy. The wear properties of Al?C20Si?C0.1P alloy have been investigated and compared with that of Al?C20Si alloy. The microstructure of Al?C20Si?C0.1P alloy consisted of primary and eutectic silicon distributed in the Al matrix. The size of primary Si is much smaller than that observed in Al?C20Si alloy. Wear tests have been conducted over a wide range of loads and sliding velocities. It has been observed that the wear rates of Al?C20Si?C0.1P alloy are lower than that of Al?C20Si alloy. The coefficient of friction is more or less constant in both the alloys but is low in Al?C20Si?C0.1P alloy. The better wear resistance of Al?C20Si?C0.1P alloy is discussed in the light of its modified microstructure evolved during solidification.     

Research on Thermal Wear of Cast Hot Forging Die Steel Modified by Rare Earths

Thermal wear of cast hot-forging die steel modified by rare earths（RE） was studied and compared with commercially used die steels. The function of RE and the mechanism of thermal wear of cast steel modified by RE were discussed. The results showed that with increasing content of RE, the wear rate of cast steel reduced at first and then increased. By adding 0.05% （mass fraction） RE, the cast hot-forging die steel with optimum thermal wear resistance was obtained, which was better than that of H13 and 3Cr2WSV. The large amount of coarse inclusions, （RE）2O2S, resulted from excessive RE, which obviously deteriorated thermal wear resistance. The mechanism of thermal wear of the modified cast die steel is oxidation wear and oxide fatigue delamination. The wear debris are lumps of Fe2O3 and Fe3O4.     

High Temperature Friction and Wear Characteristics of Fe–Cu–C Based Self-Lubricating Material

The objective of this paper is to investigate the tribological properties of a novel iron-copper-graphite (Fe–Cu–C) based self lubricating material at high temperature. The effect of Calcium fluoride (CaF₂) as a solid lubricant on friction and wear behavior of sintered Fe–Cu–C materials has been studied. Fe–Cu–C based self-lubricating materials were prepared by single stage compaction and sintering process. CaF₂ was added to Fe–2Cu–0.8C based materials in different weight percentages of 0, 3, 6, 9, and 12 wt%. The developed materials were tested for mechanical and tribological properties at high temperature (500 °C). The worn out surfaces were analyzed using a scanning electron microscope. The material with 3 wt% CaF₂ exhibited high hardness value where as compression strength of the materials decreased with the addition of CaF₂. Samples with 3, 6, and 9 wt% exhibited low value of coefficient of friction (COF) than base matrix. The material with 3 wt% CaF₂ addition exhibited better wear resistance as compared to other developed materials. The worn surfaces were mostly characterized by delaminating and abrasive wear. A high temperature solid lubricant CaF₂ was used in Fe–Cu–C based matrix and, the developed composites were tested for tribological properties at high temperature. The results showed that addition of CaF₂ in Fe–Cu–C improved the friction and wear properties. Based upon the findings, the developed material could be used for antifriction applications.