Lubrication effectiveness of composite lubricants during P/M electrostatic die wall lubrication and warm compaction

The lubrication effectiveness of the composite lubricants, 50wt% ethylene bis-stearamide （EBS） wax ＋50wt% graphite and 50wt% EBS wax ＋ 50wt% BN, during the powder metallurgy （P/M） electrostatic die wall lubrication and warm compaction was studied. The results show that the combination of 50wt% EBS wax and 50wt% graphite has excellent lubrication performance, resulting in fairly high green densities, but the mixture of 50wt% EBS wax and 50wt% BN has less beneficial effect. In addition, corresponding die temperatures should be applied when different die wall lubricants are used to achieve the highest green densities.

The influence of MoS_2 on tribology characteristic parameter of Ni60A/MoS_2 composite lubricating coating

The influence of MoS2 on the tribology characteristic parameter of Ni60A/MoS2 composite lubricating coating was researched on the UMT-2 fretting abrasion tester （USA） The result shows that with increasing content of MoS2, the hardness curve of the composite coating decreases and the trend accelerates. Under the same experimental conditions, the mass loss of plasma spray composite coating without adding MoS2 iS 1.27×10^-2 mg. When the amount of MoS2 reaches 35%, the mass loss is 0.96×10^-2 mg. It can be seen that adding MoS2 phase can improve the wear resistance, the amplitude of which is close to 30%. The friction coefficient of plasma spray composite coating without adding MoS2 is 0.23. Adding MoSz could decrease the friction coefficient of the coating and presents a downtrend. When the mass fraction is 35%, the friction coefficient is the smallest （0.13）, and the range is doubled.

Effect of lubricant sulfur on the morphology and elemental composition of diesel exhaust particles

This work investigates the effects of lubricant sulfur contents on the morphology,nanostructure,size distribution and elemental composition of diesel exhaust particle on a light-duty diesel engine. Three kinds of lubricant（LS-oil,MS-oil and HS-oil,all of which have different sulfur contents：0.182%,0.583% and 1.06%,respectively）were used in this study. The morphologies and nanostructures of exhaust particles were analyzed using high-resolution transmission electron microscopy（TEM）. Size distributions of primary particles were determined through advanced image-processing software. Elemental compositions of exhaust particles were obtained through X-ray energy dispersive spectroscopy（EDS）. Results show that as lubricant sulfur contents increase,the macroscopic structure of diesel exhaust particles turn from chain-like to a more complex agglomerate. The inner cores of the core-shell structure belonging to these primary particles change little; the shell thickness decreases,and the spacing of carbon layer gradually descends,and amorphous materials that attached onto outer carbon layer of primary particles increase. Size distributions of primary particles present a unimodal and normal distribution,and higher sulfur contents lead to larger size primary particles. The sulfur content in lubricants directly affects the chemical composition in the particles. The content of C（carbon）decreases as sulfur increases in the lubricants,while the contents of O（oxygen）,S（sulfur）and trace elements（including S,Si（silicon）,Fe（ferrum）,P（phosphorus）,Ca（calcium）,Zn（zinc）,Mg（magnesium）,Cl（chlorine）and Ni（nickel））all increase in particles.

Tribological behavior and microstructural evolution of lubricating film of silver matrix self-lubricating nanocomposite

The aim of this study is to fabricate the nanocomposite with low friction and high wear resistance using binary solid lubricant particles.The microstructure and tribological performance of the nanocomposite are evaluated,and the composition and film thickness of the lubricating film are observed and analyzed by scanning electron microscopy(SEM)and X‐ray photoelectron spectroscopy(XPS).The nanocomposite exhibited improved tribological properties with a friction coefficient as low as 0.12 and a low wear rate of 2.17×10^(-6) mm^(3)/(N∙m)in high‐purity nitrogen atmosphere.Decreasing sliding speed can increase lubricating film thickness,and the thickest lubricating film is approximately 125 nm.As the film thickness of the lubricating film exceeded 90 nm,the friction coefficient curves became smooth.In compared with WS_(2),MoS_(2) can be more effective in forming the transfer layer on the worn surfaces at the initial stage of the tribological process.