Oil-impregnated open-pored sintered materials can be used to provide the intrinsic self-lubrication of tribological contacts. Although its general functionality was recently confirmed for highly-loaded contacts, detailed analyses on the local effects of surface porosity in tribological contacts are required in order to understand and improve its operating behavior. In this context, this study investigates the influence of different surface finishes at a twin-disk test rig, and the local effects of surface porosity in elastohydrodynamically lubricated (EHL) contacts at an optical tribometer, based on thin film colorimetric interferometry. The results show the detrimental influence of high surface porosity on the operating behavior. Local observations of the lubricant film in EHL contacts indicate the presence of “open” pores, resulting in local film breakdown, and “closed” pores, transporting the additional lubricant into the pressurized zone. An appropriate surface finish technique to manufacture a low permeable layer with an adequate mechanical strength is demanded.

Local Effects in EHL Contacts with Oil-Impregnated Sintered Materials

Use of porous materials in fluid film is well established so as to make more uniform distribution of pressure along the journal surface. The work presented in this paper deals with theoretical examination into the effect of worn bearing surface on the behaviour of a hybrid double layer porous journal bearing system (DLPJBS) operating with power-law lubricants. The governing equation for the flow of non-Newtonian lubricant in the bearing porous clearance space is solved by using the FEM. The effects of non-Newtonian lubricant on the bearing characteristics of a worn bearing have been studied. Findings of this study indicates that the hybrid DLPJBS operating under non-Newtonian lubricant offers enhanced values of $${\bar{h}}_{min}$$
 , $${\bar{\omega}}_{th}$$
 and rotor dynamic coefficients (stiffness and damping coefficients).

Analysis of a double layer porous hybrid journal bearing considering the combined influence of wear and non-Newtonian behaviour of lubricant

Temperature distribution and heat generating/transfer mechanism of the circular bilayer porous bearing for thermo-hydrodynamic problem

Friction and wear enhancement of magnetron sputtered bilayer Cr–N/TiB2 thin-film coatings

This paper aims to study the tribological behavior of the WS2/oil-impregnated porous polyimide (PPI) solid/liquid composite system, in which both PFPE (perfluoropolyether) and SiCH (silahydrocarbons) oils with different hydrocarbon chains were used, respectively. Lubricating mechanism of the composite system was also explored.,The tribological behaviors of the WS2 films against the PPI cylindrical pins before and after immersing oil were evaluated under different loads by a reciprocating-type ball-on-disc tribometer.,The composite system exhibited the low and stable friction coefficient after the running-in stage, and the lubricant oil played a positive effect. It was found that the WS2/PFPE composite system exhibited more excellent lubricating property, although sole SiCH far exceeds PFPE in lubrication. The abnormal phenomenon mainly resulted from the influence of the oil amount. XRD results on the wear track surfaces indicated that PFPE and SiCH oils with different hydrocarbon chains were likely to preferentially adsorb to the edge plane and basal plane of the WS2 crystals, respectively.,In previous studies, liquid lubricants were directly dripped or spin-coated on the solid lubricant surface. Based on its potential advantage in application, the tribological behavior and mechanism of the solid lubricating film/oil-impregnated PPI composite system were investigated in this study.

Tribological behavior of WS2/oil-impregnated porous polyimide solid/liquid composite system

Purpose




The purpose of this paper is to discuss the combined effects of the deterministic surface roughness and porous structure on the lubrication property of the multi-layer bearing.




Design/methodology/approach




Digital filtering technique and Kozeny-Carman equation are used to simulate the random Gauss surface and the internal pore structure of the porous bearing, respectively. Effects of surface morphology, structure and pores on the lubrication property are discussed by using the finite difference method.




Findings




Results show that the lubrication performance of the multi-layer bearing increased with the increase of the surface roughness. Also, the transverse surface is better than that of the longitudinal surface. Moreover, lubricating property is getting worse with the increase of the height of each layer and the porosity. The lower permeability surface is beneficial to improve the lubrication performance when the total porosity is certain.




Originality/value




The effect of the Gauss roughness parameters on the detail of lubrication performance are analysed, such as the migration of the oil film rupture point position, the expansion of the pressure distribution region and the fluctuation of the pressure distribution curve with the roughness parameters. The combined effects of surface roughness, multi-layer structure and the internal pore parameters on the hydrodynamic behaviours of multi-layer porous bearing are analysed. This work is beneficial for the analysis of the tribological property and the structural design of multi-layer bearing.

Effects of surface roughness and porous structure on the hydrodynamic lubrication of multi-layer oil bearing

The invention discloses a high-strength lead-free copper-base sliding bearing material and a preparing method thereof. FeS powder and bronze powder are mechanically alloyed through the ball milling technology, the interface bonding capability between FeS and copper is improved, FeS particles are evenly distributed in a copper base body, the defect that aggregating is likely to happen when the content of the FeS is high is overcome, the dispersion strengthening function of FeS can be brought into play, and the material mechanical performance is improved. According to the high-strength lead-free copper-base sliding bearing material and the preparing method thereof, the good solid self-lubricating capability of FeS is mainly utilized, the friction and abrasion performance of the lead-free copper-base sliding bearing material is improved, effective unification between the high strength and the good lubricating character of the copper-base sliding bearing material is achieved, and application of the lead-free copper-base bearing material under complex work conditions is widened.

High-strength lead-free copper-base sliding material and preparing method thereof

The invention discloses a lead-free copper-based sliding bearing material and a preparation method thereof. The raw materials comprises nickel, tin, iron, bismuth, molybdenum disulfide, phosphorus and cooper, the cooper serves as base materials, cooper-plated molybdenum disulfide and the bismuth serve as lubricating components, and lead in a bearing is replaced by a synergistic effect of the molybdenum disulfide and the bismuth; a cooper plating layer is formed on the surface of the molybdenum disulfide through a chemical plating effect, so that a combining effect of the molybdenum disulfide and the cooper base is improved, and decomposing does not happen in sintering; and the bismuth has antifriction and antiadhesion effects, the cooper-tin-bismuth powder is subjected to atomization treatment, and the situation that the brittle phase bismuth falls off from the base body is effectively avoided. According to the lead-free copper-based sliding bearing material, antifriction and antiadhesion performance is good, mechanical performance is excellent, the lead-free copper-based sliding bearing material can be used in the fields of food machinery, medicine machinery, engineering machinery and the like, and broaden application prospects are achieved.

Lead-free copper-based sliding bearing material and preparation method thereof

The invention discloses a surface sulfurizing technology for a ferrum-based powder metallurgy part. The surface sulfurizing technology is characterized in that deoiling, acid activation and drying pretreatment are firstly carried out on the ferrum-based powder metallurgy part; chemical sulfurizing is carried out at room temperature, a sulfurizing layer is formed on the surface of the part, and the corrosion of a permeating agent on a hole is reduced in the manner of combining a ph regulation agent and a corrosion inhibitor, so that the sulfurizing layer with stable performance is formed; and finally oil immersing treatment is carried out under the vacuum condition, and the oil-bearing sulfurized ferrum-based powder metallurgy part is obtained. The stable liquid-solid cooperative lubrication effect can be formed during work under the oil lack work condition, and the friction reduction performance and meshing resistance of the powder metallurgy part are remarkably improved. The technology is simple, controllable and suitable for industrial production, and energy is saved.

Tian Ming

Papers

Effects of surface roughness and porous structure on the hydrodynamic lubrication of multi-layer oil bearing

High-strength lead-free copper-base sliding material and preparing method thereof

Lead-free copper-based sliding bearing material and preparation method thereof

Surface sulfurizing technology for ferrum-based powder metallurgy part