Wear Of Grey Cast Iron Research Articles

Graphene Coating via Chemical Vapor Deposition for Improving Friction and Wear of Gray Cast Iron at Interfaces.

This study reports the influence of CVD-graphene on the tribological performance of gray cast iron (GCI) from the internal combustion engine (ICE) cylinder liners by performing a ball-on-disk friction tests. The graphene-coated specimen exhibited a significant reduction (∼53%) of friction as compared to that of the uncoated specimen, whereas wear resistance increased by 2- and 5-fold regarding the wear of specimen and ball, respectively. Extremely low shear strength and highly lubricating nature of graphene contribute to the formation of a lubricative film between the sliding surfaces and decreases the interaction between surfaces in the dry environment. Under the applied load, a uniform film of iron oxides such as Fe2O3, Fe3O4, and FeOOH is found to be formed between the surfaces. It is proposed that the graphene encapsulation with the metal debris and oxides formed between the specimens increases the lubricity and decreases the shear force. The transformation of graphene/graphite into nanocrystalline graphites across the contact interfaces following the amorphization trajectory further increases the lubricity of the film that ultimately reduces friction and wear of the material.

Effects of different bionic units coupling on the sliding wear of gray cast iron

To enhance the sliding wear resistance of gray cast iron under starved lubrication conditions, two kinds of bionic units were generated by using a pulsed Nd: YAG laser and a drill on the surface of the specimens. The microstructure and microhardness of the bionic strip unit were examined. Comparing the wear resistance of five groups of specimens (an untreated specimen; a specimen with a surface that was completely melted by the laser; a specimen containing only bionic pit unit; a specimen containing only bionic strip unit and a specimen coupling two kinds of bionic units), the results indicate that the wear resistance of the bionic unit coupling specimen is better than that of the others. The result of a stress analysis of the specimen surface shows that the bionic strip unit plays a supporting role and can reduce the stress concentration on the edge of the bionic pit unit. On the other hand, the bionic pit unit can supply lubricating oil to the wear gap, change the moving model of abrasive grains and improve the lubrication performance. The two kinds of units can protect and promote each other under starved lubrication conditions, improve the resistance to sliding wear.

Surface topography and tribology of cast iron in boundary lubrication

This work aims to study and understand the influence of the surface topography on wear of grey cast iron used for heavy duty diesel engine cylinder liners. A micro-alloyed grey cast iron was tested with different surface topographies. These were polished surfaces, honed surfaces (with two different honing parameters) and three model surfaces with well defined grooves on a polished specimen. Reciprocating friction tests using a steel ball rubbing against a flat or a cylindrical sample (extracted from a cylinder liner) were carried out on a Cameron Plint test rig. A commercial synthetic oil for diesel engine was used as the lubricant. The friction coefficient and the electrical contact resistance were measured during the tests. The wear volume of the cylinder liner part was also measured at the end of the test. The influence of the surface topography on the tribochemical film formation and on the wear behaviour of cast iron was established. Surfaces exhibiting lots of surface asperities had the highest wear, mainly due to delayed formation of protective tribochemical film. In our test conditions, the spacing between the grooves on model specimens had no influence on the wear behaviour of the cast iron specimens.

Friction and wear of grey cast iron against Si3N4 in emulsion and water

AbstractFriction and wear tests of Si3N4 against cast iron were carried out using a ring‐on‐block tester lubricated by emulsion. To provide a comparison with emulsion, distilled water was also used as a lubricant in the tests. The results show that emulsion can prevent the formation of an SiO2·2H2O film on the iron surface. Although the friction coefficient of Si3N4/ iron pairs in emulsion is much greater than in distilled water, the wear of Si3N4 in emulsion is less.

An SEM Study of Mild-to-Severe Wear Transition in Grey Cast Iron During Dry Sliding

The self-lubricating quality of grey cast iron makes it an ideal material for use in industrial applications in which continuous lubrication is difficult or even undesirable. The excellent wear resistance of the material in dry sliding is ascribed to the formation of a graphite film on the surface, derived from the graphite flakes present in its structure. It is now generally recognized that grey cast iron with a pearlitic matrix and ASTM Type A randomly distributed flake graphite of medium size 4/5 gives optimum performance. The rates and mechanisms of wear of grey cast iron in the mild and severe regimes have been studied by many investigators. However, few have examined in detail the processes occurring with increasing sliding distance or time for a specific combination of normal load and sliding velocity. This paper presents the results of such a study. The variation in frictional coefficient with increasing sliding distance was continuously monitored and combined with scanning electron microscopy (SEM) of the associated microstructural changes to provide a further understanding of the mild-to-severe wear transition in grey cast iron.

Effect of liquid lubricants on the wear of grey cast iron against Si-Al-O-N ceramic

The effect of liquid lubricant characteristics on the wear of grey cast iron against Si-Al-O-N ceramic has been investigated. The wear of the grey cast iron in the oil-lubricated condition was found to be the greatest, followed by that in the methanol- and pure-water-lubricated conditions. The Si-Al-O-N ceramic was worn considerably in the presence of water owing to an oxidation reaction.

Wear tests of grey cast iron against ceramics

The rolling wear of grey cast iron, partially stabilized zirconia, SiC and Si 3N 4 against themselves in unlubricated contact was performed at room temperature. The wear behaviour of grey cast iron against each of the above ceramics was also examined, both unlubricated and lubricated with methanol at room temperature. It was found that the wear life, defined as the onset of severe wear, was highest for the wear of silicon carbide against itself and was approximately ten times that compared with the other materials in this study. The hardness of the ceramics had a strong influence on the wear of grey cast iron in unlubricated contact. The thermal conductivity of the ceramics also influenced the wear of grey cast iron in combination with ceramics when lubricated with methanol.

Effect of phosphide and matrix microstructures on the dry sliding wear of grey cast iron

The effect of a continuous phosphide network in matrices of pearlite, ferrite, martensite, and tempered martensite has been investigated on the dry wear of a grey iron, sliding at a speed of 1.5 m s −1 with stresses of 0.5 and 2.0 MPa against cast iron. A running-in period was observed with a 0.2% P iron, whereas no running-in was observed with the 1.0% P irons. The presence of a continuous phosphide network reduced the wear rate of the pearlite iron by a factor of 0.25. In the weaker matrices (pearlite, ferrite, and tempered martensite) the phosphide network stiffened the matrix, fractured, and formed a particulate composite of phosphide in the deformed surface which resisted deformation. The wear rates and wear mechanisms of the irons are presented and discussed.

Running-in wear of a grey cast iron and the effect of laser transformation hardening

The running-in wear of a flake graphite grey cast iron in the untreated and laser-hardened conditions has been measured using a Talysurf with a precision relocation technique and the worn surface examined using scanning electron microscopy. For both types of iron wear was mainly abrasive, and no adhesive wear occured. With the untreated irons graphite was deposited on the wheel, wear continued with the higher load but reached a steady-state condition after about 100 m with the lower load, and wear followed approximately a truncation model. With the laser-hardened irons the amount of wear was reduced considerably, graphite was not deposited on the wheel, the profilometry data were irregular, and wear did not follow a truncation model. The microscopical and profilometry data are discussed in relation to the running-in process.

The influence of acid strength on the corrosive wear of grey cast irons in oil-sulphuric acid mixtures

The sliding wear of grey cast iron against similar material in base lubricating oil-sulphuric acid mixtures as a function of acid strength in the aqueous phase and of volume concentration of aqueous phase in the oil has been investigated. For all acid strengths (10%, 20%, 30% and 40%), the amount of wear increases with increasing volume of the acid phase in the oil mixture because of increasing disruption of the hydrodynamic oil film, leading to metal-metal contact and corrosion of the metal surfaces by the acid. In mixtures containing low percentages of acid in oil (5 and 10 vol.%), the corrosive-wear process is very dependent on the acid concentration. Here, the presence of 10% acid concentration in water is effective in partially disrupting the film, leading to significant damage as mechanical wear is able to take place. As the acid concentration is increased progressively to 40%, the formation of adherent protective corrosion product films reduces metal-metal contact and decreases the wear rate. In mixtures containing high percentages of acid in oil (20–40 vol.%), the amount of aqueous phase is sufficient to give long periods of metal-metal contact. In addition, the more continuous nature of this phase and the vigorous stirring motion during sliding prevents formation of adherent wear-protective films. The products of corrosion are removed rapidly away from the metal surfaces, resulting in a much enhanced wear rate with a considerable contribution from the corrosion processes.

The influence of load and surface treatment on the corrosive wear of cast iron in oil-sulphuric acid environments

An investigation into the influence of load and surface finish on the reciprocating corrosive wear of grey cast iron in oil-10 vol % sulphuric acid mixtures has been undertaken with particular respect to the contact between cylinder-lining and piston-ring materials from marine diesel engines. In mixtures containing acid of 10 vol% concentration, under loads of 1.5 to 3.5 kg, the hard-phase phosphide eutectic/alloy carbide material in the cast irons was able to support the load and aid in the retention of an oil film during sliding. However, at a load of 4 kg the hard-phase material was able to penetrate the oil film more effectively and contact the countersurface for long periods, giving considerably increased wear rates. In mixtures containing acid of 40% concentration, the wear rates were less than those of 10% concentration, due to formation of adherent, wear-protective corrosion-product films. These were particularly effective at loads of 1.5 to 2.0 kg, while at 2.5 to 4.0 kg such films were unable to be sustained on the hard-phase regions and wear rates were increased to some extent, although were still much less than in the 10% acid concentration mixture. During sliding in mixtures containing acid of 40% concentration, development of a wear-protective film was influenced very markedly by the surface finish of the cast-iron specimens. Corrosion-product films were able to develop more easily on rough surfaces (120 grit) than on smooth surfaces (1 μm), while hydrodynamic oil films could develop more easily on smooth surfaces. The overall result was that the wear rate increased with decreasing surface roughness from 120 grit to a maximum at an intermediate value (800 grit), and then decreased with further decrease in roughness to 1 μm.

Dry sliding wear of grey cast iron containing 0.2–1.0 wt.% P

The effect of 0.2, 0.4, 0.6, 0.8 and 1.0 wt.% P on the dry sliding wear of a grey cast iron using a steel-pin-on-ring technique with a speed of 1.5 m s −1 and mean normal stresses of 0.5, 1.0, 1.5 and 2.0 MPa has been investigated. A uniform pattern of wear behaviour occurred. Severe wear of the 0.2 wt.% P iron occurred at all stresses. The presence of phosphorus reduced the wear rate progressively at all stresses; at the lowest stress 1.0 wt.% P results in the most mild wear and at the highest stress all irons suffered severe wear. Metallographic features of the surfaces and sections are related to the results.

The effect of laser surface melting on the cavitation wear of grey cast iron in distilled and 3% salt waters

Vibratory cavitation erosion tests were used to investigate the effects of laser surface melting and 3% salt water on the cavitation erosion of a grey cast iron. Laser surface melting reduced the amount of cavitation erosion in distilled water by a factor of 0.3 and in 3% salt water by a factor of 0.57. Salt in the water increased the amount of erosion of the untreated iron by a factor of 2.1 and the laser-treated iron by a factor of 3.94. Surface profiles and metallographic studies were made at stages throughout the cavitation test and these are discussed and related to the cavitation erosion process.

Physicochemical foundations of the wear of gray cast iron under conditions of plastic deformation

1. Alloying cast iron with elements such as molybdenum, vanadium, titanium, chromium ensures greater strength of the metal matrix and its greater resistance to plastic deformation and lesser reduction of hardness when it is heated. 2. Graphite inclusions and nonmetallic inclusions, being stress raisers, cause crack nucleation under conditions of elastoplastic deformations of the friction pair. 3. The increased wear of unalloyed cast iron is due to the intense loss of strength of the surface layer of metal under the effect of elevated temperatures and of plastic deformation in the zone of contact of the elements of the friction pair.

Influence of load and speed on wear characteristics of grey cast iron in dry sliding — selection for minimum wear

The wear of grey cast iron in dry sliding conditions has been studied with the aims of (1) finding the influence of working conditions on the wear rate, and (2) determining the region of speed and load where low wear is accomplished. Grey cast iron with flake and nodular graphite was submitted to investigation using a pin-on-disc machine. The results indicate that the flake graphite cast iron is more suitable for applications at speeds greater than 4 m s −1 and lower loads, while nodular cast iron has greater wear resistance at lower speeds in the range of loads investigated - from 50 N cm −2 to 200 N cm −2

Wear of gray cast iron

Wear of gray cast iron

Sparking wear of grey cast iron

The mechanism of sparking wear of different grey cast irons during dry rubbing contact on a steel cylinder has been investigated. The sparking wear rate is 5 to 10 times greater than the normal wear rate. A contributory factor is the ferrite content of the grey cast iron.

鼠鋳鉄のころがり軽摩耗―アムスラー式摩耗試験機による研究―

In order to study the rolling wear of gray cast iron accompanied by sliding, the mild wear tests were carried out under the dry condition using the upper and lower test pieces of gray cast iron of the same quality. A modified Amsler wear testing machine was used with the load of 3∼60 kg, and at the sliding velocity of 0∼0.27 m/sec combinating the test pieces of various diameters. Results are summarized as follows. (1) The wear process within this experimental limits is understood as the oxidative wear, and the mechanical wear, or mixed, but does not lead to the scuffing. (2) There is a critical point (P=14 kg/mm2) between the wear loss and the stress (maximum Hertz stress), and the wear loss shows a rapid rate of increase beyond it. (3) At the stress higher than 11 kg/mm2, the amount of wear loss of the lower piece is greater than that of the upper one. (4) Chemical analysis of wear particles by means of X-ray diffractometer shows that the amount of Fe2O3 is larger than 50% in weight in the oxidative region, 10∼50% in the transient region and almost zero in the mechanical region.