Friction and Wear Behavior of Steels under Different Reciprocating Sliding Conditions

The friction and wear behavior of ISO 100Cr6 steel ball sliding against conventionally hardened carbon and low-alloy steels was studied. The effect of hardness, hardening capacity, normal load, and sliding speed on the coefficient of friction and friction energy was investigated. Friction tests were carried out, without lubrication and under ambient conditions, on a reciprocating friction tester in which a ball-on-flat contact configuration was adopted. The results showed that there is a relative tendency for the friction properties to decrease with increased hardening capacity and decreased hardness. The results showed that increasing normal load decreases the coefficient of friction for the two steel nuances. However, increasing sliding speed increases the coefficient of friction of low-alloy steel and decreases the coefficient of friction of carbon steel. The oxidation of wear debris influences the wear mechanisms and friction behavior.     

Wear of Aluminum-Alloy Matrix Composites in Lubricated Conformal Contact with Case Hardened Steel

The wear behavior of SiC particle-reinforced aluminum alloy matrix composites as journal bearing materials in conformal contact against case hardened AISI 1016 steel under mixed lubrication conditions using SAE 10W30 oil was investigated. The bearings exhibited weight gain, followed by weight loss and subsequent weight gain as the sliding distance increased. Iron transfer and tribo-chemical reaction product formation were responsible for the observed weight gain. The surfaces of the composites contained transferred iron, layers rich in Fe, S, P and Zn, and hard tribo-deposits of high phosphorus concentration. The hard tribo-deposits were thought to be an important factor in lubrication breakdown and contact failure.     

Wear behavior of different surface treated cam spindles

In this study wear behavior of cam spindles made of five different surface treated nodular cast iron (GGG50) and induction hardened CK45 steels was investigated. In the experiments; PVD–TiN-coated, both borided and PVD–TiN-coated, only hardened, both hardened and PVD–TiN-coated and only borided spherical graphite cast iron and induction hardened CK45 were used. The wear behavior of two type of steel was observed using cam wear mechanism under unlubricated and six different surface treatments. AISI 4140 steel was used for abrasive plate. The boronizing process was realized in a salt bath consisting of borax, boric acid and ferro-silicon at 900 °C for 6 h and appropriate boronizing heat treatment was carried out under atmospheric pressure. Borides, e.g. FeB, and Fe₂B formed on ductile iron was verified by scanning electron microscope (SEM) and the distribution of alloying elements was detected by means of energy dispersive spectroscopy (EDS) from the surface to the interior. The weight loss amounts were determined as a function of sliding time and sliding velocity. In the result of the experiments; boriding and PVD–TiN coating were successfully applied to GGG50 spherical cast iron. These surface treatments increased the wear resistance of GGG50 material.     

Wear behaviour of laser cladded and plasma sprayed WCCo coatings

The usefulness of WCCo cermets as wear resistant material for coatings is determined by the cladding technique employed. This paper compares the features of an 83% WCCo coating on an AISI 1043 steel substrate using two different application techniques: plasma spraying and laser cladding. Results show significantly less porosity, improved coating hardness and better layer-substrate adherence in laser cladded than in plasma sprayed coatings. This causes them to have different wear behaviour which was determined using a method developed on the basis of the PV factor theory using sliding linear contact of flat-cylinder type. The method proved that wear rate (V_d′) is directly proportional to the product of coefficient of friction (μ), load (C) and applied speed (V), V_d′ = KμCV, where proportionality constant, K, is different for every material and depends on conditions such as lubrication, temperature, etc. To study wear behaviour, laser cladded and plasma sprayed 83% WC-Co coatings, under extreme lubrication, were placed against a hardened and tempered AISI 1043 steel, at different load and sliding speed rates. As a result constant K was estimated for each coating. The tests also showed that wear rate in laser deposited coatings is approximately 34% lower than in plasma sprayed coatings.     

Friction and wear properties of bronze–graphite composite under water lubrication

Bronze–graphite composite was prepared using powder metallurgy. The friction and wear behaviors of the resulting composites in dry- and water-lubricated sliding against a stainless steel were comparatively investigated on an MM-200 friction and wear tester in a ring-on-block contact configuration. The wear mechanisms of the bronze–graphite composite were discussed based on examination of the worn surface morphologies of both the composite block and the stainless steel ring by means of scanning electron microscopy equipped with an energy dispersion spectrometry and on determination of some typical elements on the worn surfaces by means of X-ray photoelectron spectroscopy. It was found that the friction coefficient was higher under water lubrication than that under dry sliding and it showed margined change with increasing load under the both sliding conditions. A considerably decreased wear rate of the bronze–graphite composite was registered under water-lubricated sliding than under dry sliding, though it rose significantly at a relatively higher load. This was attributed to the hindered transfer of the composite onto the counterpart steel surface under water-lubricated sliding and the cooling effect of the water as a lubricant, while its stronger transfer onto the steel surface accounted for its higher wear rate under dry sliding. Thus, the bronze–graphite composite with much better wear-resistance under water-lubricated sliding than under dry sliding against the stainless steel could be a potential candidate as the tribo-material in aqueous environment.     

Wear Behavior of Cooling Slope Rheocast A356 Al Alloy

In the present study, the dry sliding wear behavior of rheocast A356 Al alloys, cast using a cooling slope, as well as gravity cast A356 Al alloy have been investigated at a low sliding speed of 1 ms^?1, against a hardened EN 31 disk at different loads. The wear mechanism involves microcutting–abrasion and adhesion at lower load for all of the alloys studied in the present work. On the other hand, at higher load, mainly adhesive wear along with oxide formation is observed for gravity cast A356 Al alloy and rheocast A356 Al alloy, cast using a 45° slope angle. Unlike other alloys, 60° slope rheocast A356 Al alloy is found to undergo mainly abrasive wear at higher load. Accordingly, the rheocast sample, cast using a 60° cooling slope, exhibits a remarkably lower wear rate at higher load compared to gravity cast and 45° slope rheocast samples. This is attributed to the dominance of abrasive wear at higher load in the case of rheocast A356 Al alloy cast using a 60° slope. The presence of finer and more spherical primary Al grain morphology is found to resist adhesive wear in case of 60° cooling slope processed rheocast alloy and thereby delay the transition of the wear regime from normal wear to severe wear.     

GCr15及G20CrNi2Mo轴承钢高温润滑条件下摩擦磨损性能

为了探究轴承钢在高温润滑条件下的摩擦磨损性能,采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、洛氏硬度计等对GCr15高碳轴承钢和G20CrNi2Mo渗碳轴承钢组织、物相及硬度进行了表征,利用QG-700型气氛高温摩擦磨损试验机研究轴承钢材料不同条件下的高温润滑摩擦磨损性能,并分析其磨损机制.结果表明:2种轴承钢...     

Transition wear behaviour of an abrasion-resistant cast iron

The transition wear behaviour of an abrasion-resistant cast iron was examined using a laboratory test apparatus which models sliding abrasive wear. Low carbon and high carbon 15Cr-3Mo cast iron in the as-cast and hardened condition were used. Loads from 7 to 156 N were applied via a diamond indenter which was used to cut the grooves in the specimen surfaces. The volume of the grooves and the wear coefficients were calculated. A transition in wear was observed when the critical plastic deformation was exceeded. The transition is explained by the onset of unstable cracking in the process of particle separation; this is revealed by scanning electron microscopy.     

Wear and friction of synthetic esters in a boundary lubricated journal bearing

This study concerns the case of a slow intermittent motion, conformal contact, high load bronze journal bearing against a hardened steel shaft lubricated in an oil bath at a temperature about of 13 °C. Three synthetic esters were used: one pure and two formulated ones. Worn surfaces were examined using SEM-EDS to determine the wear mechanism. The tested lubricants were examined using ICP-AES to identify the elements present.The results show the wear rate, friction and temperature in the subsurface of the journal bearing material. An initial bronze–steel contact develops into a copper–copper contact along the sliding distance. Wear element concentration in the oil and friction surfaces departs from the elementary concentration in the journal bearing bronze base material. The copper layer thickness depended on additives in the synthetic esters, load and wear rate.     

Effect of Normal Load and Sliding Distance on the Wear Behavior of NiTi Alloy

Effect of normal load and sliding distance on the room temperature dry sliding wear behavior of a Ti-50.3 at% Ni alloy against a bearing steel was studied. The wear tests were conducted using a pin-on-disk tribometer under normal loads of 20, 40, 50, 60 and 80 N for sliding distances up to 1000 m. The wear results showed that the wear rate of NiTi alloy decreased as the normal load increased from 40 N to 60 N. Formation of iron rich tribological oxide layers under the higher loads could be the main reason of decrease in the wear of NiTi alloy. Increasing the sliding distance decreased the wear rate of NiTi alloy under normal loads of 60 N and 80 N, which was attributed to the formation of more stable iron rich tribological oxide layers on the worn surfaces of NiTi alloy.     

Sliding wear behaviour of Zinc–Nickel alloy electrodeposits

The sliding wear behaviour of zinc–nickel electrodeposited coatings on mild steel substrates was investigated using a spherical pin-on-disc apparatus. The pin materials were alumina and hardened steel. The composition of the coatings was the following: 86 wt% zinc–14 wt% nickel. The friction coefficient of zinc–nickel coating against alumina counter spheres was found to be higher than that against hardened steel counter spheres. The weight loss of zinc–nickel coating after sliding against hardened steel counter spheres was found to be lower than that against alumina counter spheres. The main wear mechanism of the zinc–nickel coating sliding against stainless steel was noted to be severe shearing of the surface layers of the coating due to the ploughing action of the steel pins. For the wear experiments of zinc–nickel coatings against alumina spheres, a surface delamination mechanism is proposed to be the predominant wear mechanism of the coatings.     

Tribological Behavior of Patterned PVD TiN Coatings on M2 Steel

A series of lubricated pin-on-disk wear experiments were performed to investigate the tribological behaviors of in-line (IN) and staggered (ST) patterned PVD TiN coatings as well as a fully TiN-coated (FC) coating on M2 steel against ASSAB 17 tool steel mating pins. The influence of applied load on the tribological behavior of the individual types of coating was also investigated. The experimental results showed that the tribological behavior of the two patterns and the FC M2 steel sliding against tool steel was a function of applied load. The wear resistance for any PVD TiN coating pattern was relatively higher at the specific individual loadings of 394, 800, 900 and 1100 N for 4 h under wet lubrication. Wear loss of the two types of patterned discs and pins was lower than that of the full coating counterpart. Wear mechanisms are suggested.     

The effect of phosphating on the friction and wear properties of grey cast iron

The friction and wear resistance of two commercial manganese phosphate coatings have been evaluated. Grey cast iron wear pins were treated by the two processes and were tested by sliding against a steel disc, under both lubricated and dry sliding wear conditions.Phosphating increases the sliding distance to scuffing as well as the scuffing load, whilst marginally reducing the coefficient of friction. No advantage was found in phosphating dry sliding surfaces.Phosphating reduces the likelihood of adhesive wear in marginal or poorly lubricated sliding couples. The choice of phosphate coating is primarily dependent on the surface finish of the sliding counterface; thin coatings are suitable if the counterface is smooth but thicker coatings are superior against rougher surfaces.     

脂肪醇对Ti6Al4V/钢摩擦副摩擦磨损性能的影响

采用SRV型摩擦磨损试验机分别考察了Ti6Al4V/钢摩擦副在多种脂肪醇润滑下的摩擦磨损性能。结果表明,与液体石蜡相比,碳链长度小于碳8的脂肪醇作为Ti6Al4V/钢摩擦副的润滑剂表现出良好的润滑性能,其润滑机制是在Ti6Al4V磨损表面形成吸附膜。载荷和频率明显影响Ti6Al4V/钢摩擦副在脂肪醇润滑下的摩擦磨损行为和摩擦磨损机制:当载荷较小时,Ti6Al4V磨损表面主要发生轻微的擦伤;随着载荷增加,Ti6Al4V磨损表面擦伤严重并在更高载荷下发生较为严重犁沟和塑性变形。     

Friction and wear behavior of flame-sprayed PEEK coatings

Polyetheretherketone (PEEK) becomes of great interest to applications as bearing and slider materials. In this paper, PEEK coatings with three kinds of crystallinities were deposited using the flame spray process. Employing a uniform design experiment, the friction and wear behavior of the three PEEK coatings were systematically investigated under dry sliding conditions against a 100C6 counterbody on a ball-on-disc arrangement for several loads and sliding velocities. For the three coatings, the friction coefficient significantly followed the normal distribution. The average friction coefficients appeared to decrease while increasing the sliding velocity, but were insensitive to the applied load in the range of investigation. Among the three coatings, the higher the crystallinity of the coating, the lower its average friction coefficient was. The wear rate of the coating with the lowest crystallinity decreased with an increase in the load and a decrease in the sliding velocity. The wear rate of the coating with the intermediate crystallinity decreased with an increase in the load, but increased with an increase in the sliding velocity at lower loads, and then decreased with an increase in the velocity at higher loads. The wear rate of the coating with the highest crystallinity decreased with the increase of both the load and the sliding velocity. The wear mechanisms of the different coatings are explained in terms of plastic deformation, plogh marks and fatigue tearing.     

Adhesive wear of stir cast hypereutectic Al–Si–Mg alloy under reciprocating sliding conditions

This paper describes an attempt to enhance the wear properties of hypereutectic cast aluminium–silicon alloys produced by semi-solid metal (SSM) processing technique. The rheological experiments on SSM slurries were performed under continuous cooling condition from liquidus temperature. Wear characteristics of alloy under investigation were studied using pin on flat wear system over a range of normal load (10–40 N) at constant average sliding speed (0.2 m/s) against cast iron and stainless steel counter surface. Stir cast alloy showed lesser weight loss compared to conventional cast alloy. Stir cast and conventional cast alloys showed higher weight loss against the stainless steel as compared to that against cast iron counter surface. Optical microscopy of the conventional cast and stir cast hypereutectic alloy has shown that stir casting causes refinement of primary silicon particles and modification of eutectic silicon compared to conventional cast alloy. The scanning electron microscopy of wear surfaces was carried out to investigate the mode of wear.     

Sliding wear behaviour of ZrN and (Zr, 12 wt% Hf)N coatings

In the present study, the sliding wear resistances of ZrN and (Zr, 12 wt% Hf)N coatings deposited on a hardened AISI D2 tool steel by arc-physical vapor deposition (PVD) technique were examined by a ball-on-disc wear tester. Alloying of ZrN coating with 12 wt% Hf did not change the hardness significantly, but achieved an improvement on adhesion strength and dry sliding wear resistance against steel (AISI 52100-55HRC) and Al₂O₃ balls.     

Wear and scuffing characteristics of composite polymer and nickel/ceramic composite coated piston skirts against aluminum and cast iron cylinder bores

The purpose of this research was to evaluate the tribological behavior and compatibility between coated piston skirts and aluminum or cast iron bore counterfaces. Aluminum piston skirts with either composite polymer coatings (CPCs) or nickel/ceramic composite coatings (NCCs) were evaluated. Among the NCC coated piston skirts, Ni–P–BN showed consistent low wear on either cast iron or the aluminum bores. The tin plated piston skirt generated low wear depths on cast iron or 390 Al bore surfaces, but higher wear depths on 413 Al or 356 Al bore. All the CPCs generated much less wear on cast iron or aluminum cylinder bores compared with the Ni–P–SiC or Ni–P–Si₃N₄ skirt coatings. Even the wear tests using 413 Al and 356 Al bores showed very low wear depths. Among the CPCs, two coatings with different percentages of molybdenum disulfide and graphite particles dispersed in the resin generated the lowest wear on 390 Al bore. Using a CPC over a hard-anodized surface, the bore wear depth was further reduced and became much more consistent compared with using a CPC alone. The response of the coatings to a simulation of the oil starvation associated with scuffing conditions revealed that the CPCs had intrinsic resistance to scuffing. However, the durability was not very good. The Ni–P–BN coating had intrinsic resistance to scuffing and good durability when sliding against 390 Al bore in the unlubricated conditions. The hard anodized surfaces with the CPCs showed much improved coating durability with good scuffing resistance.     

Tribological properties of Ni3Al-Cr7C3 composite coating under water lubrication

The tribological properties of Ni₃Al-Cr₇C₃ composite coating under water lubrication were examined by using a ball-on-disc reciprocating tribotester. The effects of load and sliding speed on wear rate of the coating were investigated. The worn surface of the coating was analyzed using electron probe microscopy analysis (EPMA) and X-ray photoelectron spectroscopy (XPS). The results show the friction coefficient of the coating is decreased under water lubrication. The wear rate of the coating linearly increases with the load. At high sliding speed, the wear rate of the coating is dramatically increased and a large amount of the counterpart material is transferred to the coating worn surface. The low friction of the coating under water lubrication is due to the oxidizing of the worn surface in the wear. The wear mechanism of the coating is plastic deformation at low normal load and sliding speed. However, the wear mechanism transforms to microfracture and microploughing at high load with low sliding speed, and oxidation wear at high sliding speed. It is concluded that the contribution of the sliding speed to an increase in the coating wear is larger than that of the normal load.     

The effect of cast iron graphites on friction and wear performance I: Graphite film formation on grey cast iron surfaces

Cast iron is assessed as a self-lubricating metal-base composite material. The formation of cast iron graphite films and the effective surface treatment of grey cast iron are discussed. It was found that the friction and wear behaviour of cast iron are influenced by the formation of a graphite surface layer. When cast iron surfaces are etched with Nital, they are found to be covered with a graphite film during the sliding friction process. This contributes to the protection of metallic contact points. The formation of graphite films during testing is assumed to be due to the non-elastic deformation of surface graphite. The effects of applied load, sliding velocity and lubricant are also discussed. The coefficient of friction increases with applied load and sliding velocity, and therefore lubrication becomes more important. These phenomena are discussed in terms of the formation of graphite films during the friction process.