The observed decreases in wear occurred because of break-down of the oxide layer to form debris, the presence of which prevented metal contact and adhesion. Although there was some scatter in the data after m of sliding, there was no evidence of any effect of pre-oxidation on overall wear, regardless of the time of pre-oxidation and it was concluded that pre-oxidation had no effect under the prescribed test conditions.
Thus, although pre-oxidation can decrease or eliminate early metal-metal contact, this cannot be guaranteed. Subsequent tests indicated the complete elimination of the severe wear regime Fig. A decrease in severe wear was also observed when stainless steel underwent pre-sliding for m at room temperature, due again to the presence of an accumulated loose oxide layer. In both cases, the availability of pre-existing oxide debris acted to prevent contact between the metallic interfaces.
The presence of accumulated oxide from pre-sliding did not, however, lead to a decrease in the rate of wear during mild wear.
A sliding speed of 28 x m. This was due to the oxygen in the surface layers assisting the formation of oxidised debris and, thus, decreasing the initial severe wear period. Certain aspects of heat treatment of the alloys and the sliding conditions were observed to affect this. For example, in the case of the chromium and carbon steels, the improvement in wear resulting from oxygen ion implantation was noticeably less for AISI and AISI B in the annealed form compared to the martensitic form; this can be seen from the data in Tables 3 and 4.
Relative humidity has a marked effect, as in the case of AISI steel, where the oxygen ion implanted material actually undergoes a higher level of wear than the untreated material. These observations were attributed to the higher plasticity of the annealed samples.
A change in the form of the debris was also observed, from a smooth oxide layer for the martensitic samples to loose debris for the annealed samples. The one exception was for AISI B steel, where the decrease was greater in the annealed state and sliding was accompanied by a change in the state of the oxide debris from the loose form to the oxide layer form. In comparison to standard pre-oxidation treatment Table 4 , wear tended to be less, with the exception of annealed AISI , where the pre-oxidised samples produced superior results, regardless of the levels of relative humidity.
Langguth et al. The generation of HT wear resistant surfaces in situ overcomes the serious limitations on materials and coatings imposed by HT wear conditions. These events, under certain conditions of temperature, pressure and speed [,12,,23,24,] lead to the formation of surfaces with self functionalised HT wear resistance. It was thus concluded that the observed low wear and friction arise from the physical properties and condition of the glaze, rather than their chemical compositions.
Further research [4,49,] allowed the identification of the following modes of compacted layer formation. The first mode is characterised by the formation of transient oxides, followed by the oxide thickening by continued oxidation by oxygen diffusion to the substrate-oxide interface and through physical defects. The second mode of formation is characterised by two stages.
Stage one involves the formation of an insufficiently thick layer due to unfavourable temperature and low alloy strength, possibly involving an extended pre-glaze or severe run-in period. Stott et al. These mechanisms [49] were seen as limiting cases for oxide debris generation, after which the build-up of oxide to form compacted layers continued: Oxidation — scrape — reoxidation: This involves a two-stage process.
In the first step, oxide generation takes place in the areas of contact between the two sliding surfaces, with general oxidation over the apparent sliding area of contact and, also, at asperity contacts where temperatures exceed the general temperature in the region of the sliding area of contact. In the second stage, this oxide is removed by subsequent traversals of the sliding interfaces, exposing fresh metal for further oxidation.
The debris formed may then be either completely removed from the interface, act as a third body abrasive, thereby contributing to the wear process or be compacted to form a wear-protective oxide layer. Total oxidation: Under certain conditions, particularly high ambient temperatures, oxide generated during sliding or even present prior to the commencement of sliding, is not completely removed by subsequent traversals of the sliding interfaces, allowing the oxide to thicken with time.
Provided this layer is coherent and adherent to the metal substrate and can withstand the stresses of sliding, a plastically deformed wear-protective oxide layer can develop. Metal debris: Debris particles generated during the early stages of wear are broken up by the sliding action, with any fresh areas of exposed metal being subject to further oxidation. There may be a high level of oxidation of the debris surfaces, due to the relatively large exposed surface area of metal.
Enhanced oxidation is promoted by heat of deformation and increased energy of the particles due to increased defect density and surface energy the exposed surface area of debris material will increase as particle size decreases. The resulting oxide can later develop into a wear-protective layer. The formation of compacted layers has also been observed by Wood et al. The one major difficulty with these mechanisms is that they were developed from work on low speed reciprocating sliding wear, where frictional heating is not such an important factor [60].
At sliding speeds of greater that 1 m. While this adhesion force is weak, friction levels for mechanism 4 are lower than those for mechanism 2 ; however, increasing this adhesion force above a critical level results in a situation where the reverse is the case. Skidding then becomes the dominant mechanism, with no relative movement between neighbouring particles — an increase in adhesion force locks them in place. There is a transition from metal-metal wear to contact between these primarily oxide particle layers, at which point increases in contact resistance and decreases in levels of wear are coincident.
Removal of this more loosely compacted material by ultrasonic cleaning in acetone left behind the more compacted debris, load-bearing areas. These observations clearly indicate that temperature is a major driving force for adhesion between particles and formation of load-bearing compacted debris layers.
The compacted layers formed during the sliding phase of the test became solidly sintered together as a result of the subsequent heating of the samples. The effect of a very small particle size would be to increase the available surface energy, due to the resultant increase in relative surface area. This would act to drive the adhesion and sintering processes and allow for observable sintering at temperatures where sintering of the larger particles used in powder technology applications would not be noticeable.
As adhesion itself is temperature-dependent, increases in temperature due to ambient or frictional heating would accelerate the adhesion and, therefore, the sintering process. From experimental observations, Jiang et al.
Generation of wear particles due to the relative movement of the metal surfaces; 2. Removal of some particles from the wear tracks to form loose wear particles; 3. Retention of other particles within the wear track; 4.
Comminution of the retained particles by repeated plastic deformation and fracture, with particles freely moving between the rubbing surfaces and undergoing partial or even complete oxidation, due to continued exposure of fresh metallic surfaces during comminutation; 5.
Continued fragmentation and agglomeration at various sites on the wear surfaces, due to adhesion forces between solid surfaces originating from surface energy and the formation of relatively stable compact layers. This has two effects, viz: i. Firstly, material loss is reduced by a material recycling effect of the wear debris particles. Material breaking away from the compacted debris may rejoin it. Secondly, due to heavy deformation and oxidation of the wear debris particles, the layers formed are hard and wear-protective.
Two competitive processes then occur during subsequent sliding, i. The compacted layers are continually broken down, the debris generated promoting wear though, again, reincorporation may occur. Continuing sintering and cold welding between particles within the layers, leading to further consolidation. For the latter case to predominate, the temperature must be high enough in excess of a critical temperature to encourage the sintering processes required to ensure the formation of a solid wear-protective layer on top of the compacted particle layers before the layers are broken-down.
The effects of this can be seen in the experimental work of Jiang et al. However, Jiang does account for debris removal from the system leading to wear as would occur in, for example, high speed unidirectional sliding [,,] or debris removed by introduced interfacial airflow [45].
Incoloy MA versus Stellite 6 , despite the more adverse sliding conditions. Weight changes after 4, m of sliding were extremely low for all temperatures, with the largest mean change being 0. The following discussion focuses on the situation at room temperature and oC. The data in Fig. Coefficient of friction levels Fig.
The results indicate elemental transfer from the counterface to the specimen and mixing of the transferred and host element oxides. The associated selected area diffraction SAD pattern Fig. Dark-field images Fig. This is consistent with the structural variations observed by TEM. The latter exhibits a fine-grained structure 5 - 20 nm with irregular shaped grain boundaries. The particles are larger close to the interface up to about 50 nm. The quantification is based on theoretical k-factors and uses a thickness correction for an estimated nm sample thickness EELS thickness measurements indicate a thickness of nm mean free path.
Quantitative analysis of the Nimonic 80A layer Area 1 gives the characteristic composition of the bulk alloy Table 5 , apart from a slightly higher silicon concentration and a small amount of cobalt.
The interface layer consists of a mixture of Nimonic 80A and Stellite 6, with a higher than average titanium concentration []. There are some variations in the chromium, cobalt and oxygen concentrations as well as a few distinct particles with a high nickel concentration. Furthermore, this line trace also confirms aluminium enrichment at the interface; moreover, this Al2 O3 layer is between the TiO2 layer and the Nimonic 80A substrate.
The atomic numbers of chromium 24 , cobalt 27 and nickel 28 are similar and compositional variations of these main elements do not explain the strong contrast observed in the HAADF-STEM image Fig. Furthermore, a low oxygen concentration coincides with a low chromium concentration; local EDX analysis shows a low chromium and oxygen concentration for the particles that appear bright in the image. This implies that some of the nickel and cobalt particles are not completely oxidised.
EDX line traces in an area up to about one micron below the interface reveal the preferential segregation of light elements, especially aluminium and in some cases titanium Fig.
These results clearly indicate the formation of a wear resistant nanostructured surface during sliding wear of Nimonic 80A against Stellite 6 at 20oC using a speed of 0. The analyses reveal the complex structure of this surface, which consists of multiple layers: 1 A loose, uncompacted, highly oxidised layer. The nickel concentration from the Nimonic 80A is uniform throughout the whole layer, except for the presence of several larger non- oxidised particles that were randomly dispersed in the glaze.
The compositions indicate the presence of elements from both Stellite 6 and Nimonic 80A, but chromium- enriched. Slight chromium depletion was observed. The larger dark areas perpendicular to the interface were also due to aluminium enrichment. Additionally, it is apparent that the high Cr activity in both counterface and sample materials leads to the formation of Cr2O3 preferentially in the early stages of the process.
Quantification of the results on average gives The interfacial layer consists of grains of nm and has a higher dislocation density. The layer just beneath the interfacial layer shows subsurface deformation and elongated grains. The poorly- defined irregular boundaries indicate non-equilibrium high-energy configuration.
Sub-surface deformation is illustrated in Fig. Dislocations, present as networks inside the deformed elongated grains, have been observed in the deformed substrate. Shearing deformation took place in the substrate as a response to the sliding process.
The creation of nano-structures is confirmed by the STM topography, indicating grains of between 5 and 10 nm Fig. It has been indicated by various authors [3,19,20,] that, in many systems, surfaces with ultra-fine structure are generated during high temperature sliding wear. Mechanical mixing involving repeated welding, fracture and re-welding of the debris generated from both contacting surfaces is responsible for the generation of the ultra- fine structured surfaces.
Moreover, the detailed TEM studies presented here has enabled understanding of the formation mechanisms of wear resistant nano-structured surfaces. These processes are aided by high temperature oxidation and diffusion.
The positron annihilation studies confirmed the presence of vacancy clusters consisting of five vacancies []. The next stage in the process involves deformation of oxides and generation of dislocations, leading to the formation of sub-grains. High internal stress is created inside the grains; the dislocation density and arrangement depend on the grain size, with smaller grains containing fewer dislocations.
The process leads to the formation of high energy grain boundaries with a high defect density []. Several authors have also constructed wear maps in an attempt to present wear data in a more easily understood format, allowing prediction of likely wear mode under specified sliding conditions.
Lim [,] Fig. Adachi et al. The following section discusses recent developments in high temperature wear maps made by the present authors, following a brief review of earlier work by Lim. This showed that the selection of sliding conditions and configuration can greatly affect the wear behaviour and transitions observed, with load, sliding speed and temperature potentially having a large influence on the boundaries between the different modes of wear.
For example, it can be seen that, if a relatively high fixed load is used, with increasing sliding speed, a transition from severe-to-mild wear is observed Welsh [26]. More complex forms result at lower loads when sliding speeds are at much higher values Archard and Hirst [31], and Welsh [26]. To summarise, when two surfaces are worn against each other, the outcome can be a variety of apparently contradictory results.
Thus, mapping is necessary to understand the relative behaviours in different tests and the potential outcome under a given set of sliding conditions.
The weight change data are presented in Figs. For both systems [22], mild wear with low weight loss dominates at 0. At all temperatures, there was virtually no initial severe wear period, with sufficient Co-Cr oxide debris forming extremely rapidly.
The Nimonic 80A versus Stellite 6 system [21] is characterised by three distinct wear regimes at 0. The sliding behaviour at 0. The behaviour for the Incoloy MA versus Stellite 6 system follows the same general pattern at 0.
However, in this case, the high temperature mild wear regime confers protection, with the mixed Fe-Cr and Co-Cr oxides at 0. Such sliding studies indicate the potential for complex behaviour during sliding of dissimilar materials. In such cases, the necessity for mapping wear behaviour to assist prediction of mild or severe wear is important, if potentially catastrophic material failure is to be avoided.
At the outset a review of some of the well-known and relevant wear theories and models, supported by experimental findings on conventional and advanced materials, has been presented.
This background information has provided a framework to discuss new areas of high temperature wear. In this context the high temperature wear behaviour of those materials which have provided new information has been considered. Particular attention has been focussed on high temperature wear behaviour of Oxide Dispersion Strengthened and Nimonic alloys, and intermetallic materials involving like-on-like and unlike-on-unlike combinations. The most significant part of this chapter includes the exposition of the phenomena of glaze formation at fundamental levels.
The second solid may be in the form of a second body the opposing sliding surface or third body wear debris. The hard particles or surface must be 1. Such forces may include chemical bonding chemical adhesion , inter-solubility diffusive adhesion , Van-der-Waals forces dispersive adhesion and electrostatic forces electrostatic adhesion. Surface interlocking may also occur mechanical adhesion via material filling surface voids or pores. Adhesion is of greater influence during contact of clean metallic surfaces and thus during severe wear , as there are no contaminants to prevent this contact.
Adhesion is also more effective in a vacuum, where there is no surrounding atmosphere to affect it. Adhesion is normally used to describe attraction between dissimilar molecules and cohesion between like molecules.
The higher the value, the greater the ability to resist movement. Beyond this, the oxide becomes unstable, generating a wear particle. This assists the propagation of sub-surface cracks, which link together and allow surface material to break away. Such a process leads to the generation of the large, flat, angular debris seen during severe wear. HIPped hot A method of alloy or material production by powder metallurgy isostatically methods, using a combination of temperature and isostatic pressed pressure to produce the final item.
Such materials typically have a highly ordered crystal lattice structure composed of the constituent parts, but not necessarily the same as any of the constituent parts. During sliding wear i. This mechanically alloyed material may then potentially re-adhere to either parent sliding surface.
Where the two sliding surfaces are metallic, the debris being generally non-metallic prevents adhesion and metallic transfer.
Coefficient of friction values are thus usually much lower. Wear values are generally, but not always, lower than severe wear, however, such debris can act abrasively and instead enhance wear. Ploughing is also referred to more specifically as the physical deformation due to a harder material being pushed through a softer material where adhesion forces are weak.
Formation of wear debris particles cannot be clearly seen at the point of contact. Positron A major technique in Materials Science, originally applied in Annihilation PA condensed-matter physics, now widely used in metals and alloys to provide information on defect structures. Scanning A type of microscope in which the surface of a sample is scanned Electron with a high energy beam of electrons.
An image of the sample Microscopy surface is created from secondary electrons that are ejected from SEM it. Scanning A variation of TEM in which the electrons pass through the Transmission specimen and the electron optics focus the beam in to a narrow Electron spot over the sample in a raster.
Scanning An imaging technique based on the concept of quantum Tunneling tunneling. At low voltage the tunneling current is a function of local density of states LODS at the Fermi level of the sample.
The changes in current accompanying the tip movement over the surface are translated in to an image. Scanning A technique employed within an STM, to probe the local density Tunneling of electronic states, and band gap of surfaces and materials on Spectroscopy surfaces at the atomic scale.
This allows investigations of small areas 5 angstrom diameter, the area in which the tunneling current flows. As the Pattern SAD wave length a fraction of a nano-metre and the spacing between atoms are comparable, the atoms act as diffraction gratings to the electrons. Some of the electrons are scattered to particular angles determined by the material crystal structures allowing identification and analysis and form a spot pattern image on the TEM screen. Such wear is characterised by high coefficient of friction values, high levels adhesion, plastic deformation and to varying degrees, mainly metallic material transfer between the surfaces.
Also typical of severe wear is the generation of large, flat, angular, generally metallic wear debris with sizes of up to 0. In tribology, changes in torque due to sliding surface contact can be used to determine the coefficient of friction.
Transmission A widely used technique in Materials Science where an electron Electron beam is transmitted through a thinned sample placed in vacuum Microscopy with a typical energy of KeV. The electron beam is then TEM focussed by a series of magnetic field lenses into a typical spot of diameter nm.
A TEM image is created from those electrons that pass through the sample. Derived from the Greek verb "tribo" , meaning 'to rub'. Vickers Hardness A parameter defining the hardness of an engineering material.
The size of the indent created is used to obtain a measure of materials hardness. This may be metallic dominant during severe wear or oxide dominant during mild wear. Material is pushed up ahead of asperities on the counterface, resulting in a grooved wear scar with transverse cracks.
Wood, Ph. Rose, Ph. Inman, Ph. Stott, D. Lin, G. Johnson, P. Moorhouse, J. Aoh, J-C. Stott, J. Glascott, G. Gee, N. Wood, P. Datta, J. Burnell-Gray, N. Jiang, F. Stott, M. Li, K. Datta, I. Inman, H. Du, Q. Inman, S. Du, J. Burnell-Gray, S. Pierzgalski and Q. Rose, P. Pierzgalski, Q. Royal Society London, A Archard and W. Oh, K-H. Yeon, H. Stott and G. Bowden and D. Heinemann, London Eyre and D. Burwell and C. Applied Physics 23 Conference on Wear of Materials, St.
New York Wiley Iwabuchi, H. Kubosawa and K. Leheup and R. Colombie, Y. Berthier, A. Floquet and L. ASME F Hiratsukam, T. Sasada and S. Glascott and G. Sullivan and N. Stott and D. Datta and J. Gray, Royal Society of Chemistry Halliday and W. Lin, F. Stott, G. Wood, K. Wright and J. Wood and C. Iwabuchi, K. Hori, and H. Wear of Materials, New York Langgath, A. Kluge and H. Kuzucu, M. Ceylan, H. Crook and C. Bartsch, A.
Wasilkowska, A. Czyrska-Filemonowicz and U. Fujita, M. Shinohara, M. Kamada and H. Soda and T. Xing and J-Y. Suh and H. Rice, F. Moslehy and J. Dowson, Publ. Elsevier, Butterworth Heinemann Zhou, M. Harmelin, J. Du, E. Kuzmann, I. Razavizadeh and T. Garcia, A. Ramil and J. Thesis, Uppsala University Stott, C.
Stevenson and G. Brandes and G. Wood, Unpublished Work. Li, J. Xia and H. Takadoum, H. Houmid-Bennani and D. Barnes, J. Wilson, F. Barnes, F. Du, P. Inman, E. Kuzmann, K. Suvegh, T. Marek, A. Metals, 2 Inman, R. Geurts, C. Du, A. Aljarany, P. Aljarany, Ph. Valiev R. Islamgalier, I. Lowe, R. Ghosh, W. Lowe and R. Valiev Ed. Mishra, S. McFadden, A.
Mishra, A. Ghosh and T. Bieler Ed. Riahi and A. Alpas "Wear map for grey cast iron" Wear Chen and A. Yang, H. Kong, E-S. Yoon and D. Kim "A wear map of bearing steel lubricated by silver films" Wear Grimanelis and T. Eyre "Sliding wear mapping of an ion nitrocarburized low alloy sintered steel" Surf. Elleuch, R. Mnif, V. Fridrici and P. Kapsa "Sliding wear transition for the CW brass alloy", Tribo.
Kato and K. Adachi, K. Kato and N. Chen "Wear map of ceramics" Wear Withdrawn References [] E. Ezugwu, Z. Wang and A. Liu, M. Yao, P. Patnaik and X. Soboyeo and T. There is direct metal-to-metal contact, allowing high levels of adhesion accompanied by plastic deformation, material transfer and the production of large flat angular debris.
Wear rate against load for a ferritic stainless steel pin worn against high speed tool steel ring, load 1 kg, speed 1. The presence of cracks and grain boundaries act as points of ingress for oxygen ions and in the case of cracks, molecular oxygen.
This means that the distance for diffusion is significantly less where cracks in the outer layers of oxide are prevalent. Low temperature oxidational wear, moderate falls large for Stellite 6 in hardness.
Corrosion a natural but controllable process. By completing this course show employers you have a strong understanding of the basics and take the first step in working towards becoming nace certified. Jacobson materials performance managing editor corrosion is a naturally occurring phenomenon commonly defined as the deterioration of a material usually a metal that results from a chemical or electrochemical reaction with its environment.
It provides a basic but thorough review of causes of corrosion and the methods by which it can be identified monitored and controlled. Nace basic corrosion course register now february 28 march 4 jubail city saudi arabia language.
Internal corrosion for pipelines basic. Active participation is encouraged through hands on experiments. The multimedia based ecourse features on demand viewing and bookmarking capabilities that enable you to complete the course as your schedule allows.
The internal corrosion for pipelines basic course introduces the fundamentals of implementing monitoring and maintaining an internal corrosion control program as part of an overall pipeline integrity management program. Nace mr sulfide stress corrosion cracking resistant material for oil field equipment hic performance of metals and alloys.
A helpful starter course for anyone in the corrosion industry basic corrosion covers the causes of corrosion as well as how to identify monitor and control it. Gamis Batik Modifikasi Kain Polos. Kumpulan Cerpen Kompas Pdf.
0コメント