Influence of electrochemical potential on the wear of metals, particularly nickel

The wear of nickel and of alloy steels under the influence of an impressed potential is discussed in terms of a model which considers both the kinetic and thermodynamic properties of the metal/electrolyte reactions and of the electrochemical reactions of oxygen, hydrogen and water. The experimental data can be interpreted in terms of the electrochemical formation of an oxide film within the wear scar and its subsequent removal by mechanical action. The voltage range over which transitions to an increased wear rate occur are related to the Tafel slopes associated with metal dissolution reactions.     

The influence of surface roughness on wear

A series of wear experiments utilizing a ball-plane configuration was performed to determine the influence of both the magnitude and anisotropy of the surface roughness on wear. It was found that: (1) wear increases with increasing roughness up to ~ V16 finish and remains relatively constant above that roughness and (2) sliding perpendicular to the lay increases wear above that for sliding parallel, with the difference becoming negligible for the finer roughness. A method of analytically relating the results obtained for ball-plane geometry to other geometries is developed.     

The influence of surface roughness on abrasive wear

Analyses are given of the mechanism of friction and abrasive wear and of the effect of surface roughness on them. Theoretical expressions are derived for ploughing, adhesion and the total friction coefficient of hard conical asperities ploughing a soft metal surface, with the assumption that the asperities of the hard metal are cones with randomly distributed slopes, the mean value of which varies with surface roughness. Simple expressions for the abrasive wear rate and the mean wear particle size are also derived on the basis of a ploughing mechanism of the hard conical asperities on the soft metal surface.A comparison of calculated values based on these theories with experimental data of single-pass wear tests for various soft metals such as copper, cadmium, lead and zinc sliding on low carbon steel plates shows good agreement. The effects of surface roughness on the tangential forces under unlubricated and lubricated conditions as well as the mean wear particle size are theoretically discussed and the theoretical results are compared with experimental data.     

The influence of surface deformation on mechanical wear

The evidence for the plastic strain of wearing surfaces and its influence upon them is briefly described. Two distinct analytical approximations are available for calculating these effects: an elasto-plastic approximation, and a rigid-plastic approximation. These lead to two different damage rules and two different methods of idealizing asperity shape. Experiments and finite element analysis help to delineate the range of application of each of these models, and their associated damage rules, but it is clear that further theoretical developments are needed if wear is to be reliably predicted for most engineering contacts.     

The influence of lubrication rate on wear behavior

The influence of lubrication rate on wear for thin film lubrication is investigated. It was found that reduction of lubrication rates below a critical level can result in significant increases in wear. It is proposed that a minimum film thickness of six to ten times the combined peak-to-peak roughness is required to achieve a wear rate that is not sensitive to changes in the rate of lubrication.     

The influence of contact geometry on friction and wear characteristics

This paper describes some results of evaluating the influence of contact geometry on tribological characteristics. Friction characteristics obtained for a distributed contact (pin‐on‐disc and block‐on‐ring), a linear concentrated contact (pin and vee‐block and block‐on‐ring) and a point concentrated contact (ball‐on‐disc and three cylinder‐cone) are presented. The wear scars were analysed using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results show different values of friction and wear coefficients for the different types of contact geometry. The paper also assesses the effect of non‐test characteristics, e. g., vibration.     

电解加工间隙中的传质过程及其对电解加工的影响

这里应用流体力学、传质学和电化学理论,分析了电解加工间隙中处于紊流状态的电解质溶液内的传质过程。在此基础上建立了阳极电流密度的计算方法,并讨论了外加电压、电解质浓度、流速等参数对电解加工的影响。     

The influence of atmospheric humidity on the abrasive wear of metals

A pin-on-disc apparatus has been used to obtain continuous simultaneous measurements of the wear and friction (sliding force) behaviour of metals on bonded silicon carbide abrasive paper under conditions of controlled humidity. Iron, mild steel and copper exhibit qualitatively similar wear behaviour: the wear rate decreases progressively with the number of passes over the same track. In contrast, the wear rate of titanium remains constant. Variation in atmospheric humidity has little effect on the wear rates of copper or titanium, although a slight effect was found in mild steel and iron. A stronger dependence on humidity was found in the friction behaviour of all four metals, as well as a corresponding relationship between humidity and the specific energy required for metal removal by abrasion. Preliminary results from single-particle scratch tests reveal changes in the contact between a single silicon carbide particle and a polished iron surface at different humidity levels. Although only tentative explanations can be made at this stage for these effects, it is evident that any proposed mechanism must account for the behaviour of both the metal and the abrasive together, rather than of one component of the system alone.     

The influence of speed on the wear of sintered iron-based materials

A pin-on-disc-type wear test rig was used to study the influence of speed on the wear of sintered iron, sintered Fe-5Cu and sintered Fe-5Cu-5C materials over a range of speeds of 0.5 –16 m s^?1 at a constant load of 40 N. With increasing speed the wear rate decreases to a minimum and then increases. Over the entire range of speeds two types of wear are observed: these are mild wear below a speed of 8 m s^?1 and severe wear above a speed of 8 m s^?1. The results are discussed in terms of friction records, wear particle size and composition, wear track study and topographic and metallographic studies of worn specimens.     

The influence of oxides on the friction and wear of alloys

Development of compacted oxides, particular y so-called ‘glazes’, on sliding metal and alloy surfaces can result in significant decreases in friction coefficients and wear rates. This paper describes how such ‘glazes’ can form on many alloys under a wide range of sliding conditions. ‘Glazes’ consist of very fine, compacted, crystalline particles of almost any oxide or oxides. Formation of the oxide, the subsequent development of the ‘glaze’, and the mechanisms by which the ‘glaze’ reduces friction and wear are discussed     

The influence of hardness on the resistance to wear by paper

Abrasive wear data for a wide range of materials sliding against paper are compared to establish a general dependence on hardness of the abraded material. Three regions for the hardness dependence are identified. In all three regions, the wear rate depends on (hardness)^?n. In the region for which the hardness of the abrasive is larger than that of the abraded material, n ≈ 1; in the region where the hardnesses are similar, n ≈ 10; in the region where the abraded material is harder, n ≈ 5.     

The influence of the composition of nanostructural PSZ powders on ceramics wear

The results of tribological testing of ceramics with the composition ZrO₂ + Al₂O₃, ZrO₂ + Y₂O₃, and ZrO₂ + Y₂O₃ + Al₂O₃ made of nanostructural powders are presented. The nanopowders have been obtained by chemical precipitation from solutions of zirconium and yttrium chloride salts. The studies have been carried out as applied to machine parts: drawing dies and bearing plugs. The dependence of the wear of friction pairs on the composition of the ceramics is shown.     

The influence of surface oxidation on the wear resistance of cast iron

This paper reports a study of the influence of surface oxidation on the wear resistance of ductile iron, grey iron and vermicular iron during dry sliding friction. The mechanisms of wear are also reported. This study shows that the effect of surface oxidation (formed under normal atmospheric conditions) on the wear rate depends on the complex functions of graphite morphology and matrix structure. Generally the presence of surface oxidation decreases the wear rate of grey iron but increases the wear rate of ductile iron and vermicular iron when the cast iron has high hardness. This trend is reversed for low hardness cast iron.     

The influence of surface roughness on friction and wear of machine element coatings

The use of low friction coatings like amorphous carbon or metal-doped carbon coatings on machine elements is constantly increasing. Most often, a surface treatment, e.g. grinding and polishing or honing, is required for optimal performance of the coated machine element. This can be time consuming and costly.In this study, the effect of surface roughness on friction and sliding wear of two different coatings, one tungsten containing and one chromium containing coating, were examined using a ball-on-disc test. Ball bearing steel plates were grinded to different surface roughnesses and coated with the two different coatings.The friction was found to depend on surface roughness where the rougher surfaces gave higher friction coefficients. The wear rate for the a-C:W coating was found to be independent of the roughness, whereas the roughness had a strong influence on the wear rate for the a-C:Cr coating. This could partly be explained by a difference in wear mechanism, where fatigue wear was observed for the a-C:Cr coating but not for the a-C:W coating.     

An electrochemical investigation of corrosive wear of electroplated nickel

Electrochemical studies have been carried out to show the influence of the chemical component in a corrosive wear mechanism of electroplated nickel. The results demonstrate that current, weight loss of the worn specimens and friction coefficient strongly depend on the applied potential.     

The influence of femoral condylar lift-off on the wear of artificial knee joints

In vivo fluoroscopic studies of patients with total knee replacements (TKRs) have shown lift-off of the femoral condyles from the tibial insert. This study investigated the influence of femoral condylar lift-off on the ultra-high molecular weight polyethylene (UHMWPE) wear of fixed bearing (FB) and rotating platform mobile bearing (RP MB) total knee replacements, using a physiological knee joint simulator. In the absence of lift-off, the RP MB knees exhibited a lower wear rate of 5.2 +/- 2.2 mm3 per million cycles (mm3/MC) compared with 8.8 +/- 4.8 mm3/MC for the FB knees. The presence of femoral condylar lift-off was found to accelerate the wear of the FB and RP MB knees tested in this study to 16.4 +/- 2.9 and 16.9 +/- 2.9 mm3/MC respectively. For the RP MB knees the increase in wear rate was more marked, resulting in a similar wear rate for both designs of knee under lift-off conditions. In both cases the medial condyle displayed more wear damage. This study has shown that a small amount of abduction/adduction lift-off and medial-lateral shift increases wear and that the increase in wear is design dependent. In this simulator test, lift-off was simulated on every cycle, whereas the amount of wear and effect of lift-off clinically would depend on the frequency of occurrence of lift-off in vivo.     

On the influence of fatigue on machine part wear

The main aspects of the relationship between fatigue and machine part wear are considered and the relevant problem is formulated. The results of an investigation of the influence of the fatigue process on machine part wear are given for diesel engine piston rings. As the results show, the solution of the problem could open up new prospects in the development of the theory of machine part cyclic wear and the details of the technology of cyclic straining treatments for increasing fatigue wear resistance.     

The influence of aspect ratio on the interface pressure distribution of cylindrical wear specimens

The interface stress distributions arising in linearly elastic cylindrical pins sliding against a flat rigid counterface are considered in this paper. Coulomb friction is assumed, and the interface pressure distribution arises by virtue of a displacement applied to the far end of the pin. Various aspect ratios are studied in order to assess stiffness effects in pin-on-disc tribotesting.     

The influence of grain size on the wear of nickel-zinc ferrite by flexible media

Wear resistance and certain other properties of a nickel-zinc ferrite were determined as a function of grain size in tests with two γ-Fe₂O₃ tapes and a CrO₂ tape. Wear resistance was found to decrease—that is, the depth of wear increased—with decreasing grain size. The CrO₂ tape caused about three times as much wear as the γ-Fe₂O₃ tapes. Microhardness and moduli of rupture improved with decreasing grain size, but the structure-sensitive magnetic properties did not. Annealing did not improve the wear resistance, but did improve the moduli of rupture and the magnetic properties.     

Dry sliding of plasma-sintered iron—The influence of nitriding on wear resistance

Samples of unalloyed iron were sintered in the presence of an abnormal glow discharge using the confined anode–cathode configuration in order to allow surface enrichment of the sample with atoms from the cathode. AISI 430 and AISI 1020 cathodes were used to sinter the iron with and without Cr enrichment, respectively. The chromium favors the formation of a hard compound layer after nitriding (with a microhardness up to 1300 HV) due to the presence of chromium nitrides. In order to evaluate the wear resistance and surface damage to the samples, dry sliding wear tests were carried out using a block-on-ring system with applied normal loads of 25–150 N. A large scatter in the experimental results was observed for the unnitrided samples. This effect was attributed to the capacity of the materials to undergo a severe-to-mild wear transition during sliding. Nitriding was found to reduce the wear rate by at least one order of magnitude. In particular, the nitrided samples enriched with chromium (540 °C) did not display any damage at 25 N, the lowest normal load used in the present investigation.