Comparative Study of Wear Behaviors of a Selected Titanium Alloy and AISI H13 Steel as a Function of Temperature and Load

A comparative study of the wear behaviors of a selected titanium alloy and AISI H13 steel as a function of temperature and load was performed on a high-temperature wear tester. The titanium alloy and H13 steel presented totally different wear behaviors with the variation in temperature and load. Their behaviors are suggested to be attributed to the protective ability of tribo-oxides and the thermal softening resistance of the matrix. Compared to H13 steel, the titanium alloy presented poor room-temperature wear resistance, excellent high-temperature wear resistance, and an extremely protective function of tribo-oxides.     

Wear and Friction Characteristics of a Selected Stainless Steel

Dry sliding wear tests were performed for 3Cr13 steel with various tempered states at 25–400°C; wear and friction characteristics as well as the wear mechanism were explored. With an increase in test temperature, the wear rate decreased accompanied by an increase in tribo-oxides. The fluctuation of friction coefficient was slight at 25–200°C but became violent at 400°C. At 25–200°C, adhesive wear prevailed due to trace or less tribo-oxides; at 400°C, oxidative wear prevailed with the predominant tribo-oxides of Fe₃O₄ and Fe₂O₃. It can be suggested that the antioxidation of the stainless steel postponed the occurrence of oxidative wear to a higher test temperature. For adhesive wear, the wear resistance, roughly following Archard's rule, was directly proportional to hardness besides the specimen tempered at 500°C with grain boundary brittleness. But for elevated-temperature wear, a better wear resistance required thermal stability and an appropriate combination of hardness and toughness.     

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.     

Study of the Influence of Contact Geometry and Contact Pressure on Sliding Distance to Galling in the Slider-on-Flat-Surface Wear Tester

One of the major causes of tool failure in sheet metal forming is wear in the form of galling. Galling is gradual buildup of adhered sheet material on the tool and leads to unacceptable scratches on the sheet surface and to components that fail to meet tolerances. Because it is difficult to reproduce operational and interactional conditions in laboratory test equipments it is hard to test, model, and predict galling initiation.

Here the authors examine how changes from elliptical to line contact geometry influenced galling initiation under dry sliding by using a slider-on-flat surface (SOFS) wear tester. A micro clean tool steel was tested against ferritic low-strength and martensitic high-strength steel sheets.

The sliding distance to galling initiation was extracted from friction data and verified by scanning electron microscopy (SEM) observations. The presence of adhesive wear on worn tools after completed tests was used as a criterion. Experimental results showed that the elliptical contact causes galling quicker than the line contact.

Applicability of experimental results depends on the relevance of test conditions, so contact pressures calculated for the described tests were compared to calculated contact pressures in a semi-industrial U-bending test and to literature data relevant to industrial applications. Good agreement between values observed for SOFS and for most selected industrial applications was found, which assume that contact pressures typical for most common industrial applications can be successfully simulated by selection of tool geometry and normal load in the SOFS tester.     

Layer-Graded Cu/B4C/Graphite Hybrid Composites: Processing,Characterization, and Evaluation of Their Mechanical and Wear Behavior

In this article, we synthesized and studied functionally graded multilayered Cu/B₄C/graphite hybrid composites. Two classes of layer-graded composites were considered: pure Cu layer with two layers consisting of different particle sizes and uniform particle volume and a pure Cu layer with a single additional layer. The properties of the layer-graded composites were compared to those of single layer composites of two different particle sizes (1–20 µm and 60–90 µm). The composites were tested for compression strength, flexural strength, hardness, density, and wear and braking performance at a range of sliding speed conditions (5, 10, 30, and 35 m/s). The microstructure of the interfaces in the layer-graded composites was characterized to determine the quality of bonding. We found that the layer-graded composites possess improved compression and flexural strength due to lower porosity and residual compressive stress in the composite layer aided by the work-hardening of the Cu layer. The presence of the ductile Cu layer improves the toughness and crack resistance properties of layer-graded composites by macrostructure toughening mechanism. The layer-graded composites possess improved wear resistance and braking performance at both low and high sliding speed conditions due to reduced third-body wear, oxidation, and softening of composites, aided by effective heat conduction through the Cu layer. Finally, the wear mechanisms operating at various speeds were discussed with the help of microscopic and X ray diffraction studies.     

Transition of Mild Wear to Severe Wear in Oxidative Wear of H21 Steel

Under atmospheric conditions at 400 °C, we studied the wear mechanism of H21 steel with different tempering states as a function of normal load. Typical oxidative wear was identified by X-ray diffraction patterns with predominant tribo-oxides of Fe₃O₄ and Fe₂O₃. Under loads of 50–100 N, mild oxidative wear prevailed for all samples, such that the wear losses of H21 steel with various tempering states showed no significant differences with characteristics of a slight plastic deformation of the substrate and single-layer oxide. In this case, the wear rate was lower, and the tribo-oxide was decisive factor in determining wear rate. Under loads of 150–200 N, the transition of mild wear to severe wear occurred in H21 steel and was characterized by: (1) a significant difference of wear losses for steel with various tempering states; (2) wear loss that started to increase faster and reached a relatively high level; (3) the appearance of significant plastic deformation in the oxide underneath the substrate and multi-layer tribo-oxide. Under a load of 200 N for the steel tempered at 700 °C, plastic extrusion prevailed with a mixed metal-oxide layer.     

The Coupling of Waviness and Heating in a Seal

Thermoviscous lubricant flow in seals and bearings is treated as a Couette flow, and a fully coupled perturbation flow, which results from waviness of the boundary, and which gives rise to uneven heat input into the solid boundaries. Differences in modes of heat transfer within the seal rings and out to the environment are separable, and determine the thermoviscous behavior of the film in a simple way. The temperature perturbation, or wave, in the film is an order of magnitude smaller than the perturbation of heat generation, justifying the assumption of isothermal and isoviscous flow.

Calculations show that materials such as C and SiC cannot be idealized as insulators when run against metals.     

Wear Behavior of Aluminum Alloys at Slow Sliding Speeds

The investigated slow sliding speeds presented in this work enable the understanding of the wear behavior on aluminum alloys and could possibly facilitate the completion of the previously proposed wear mechanism map for aluminum at this slow sliding speed range. Dry sliding block-on-ring wear tests were carried out on aluminum alloys, AA5754 (Al-Mg), AA6082 (Al-Mg-Si), and AA7075 (Al-Zn-Cu), at a very slow sliding speed range (<0.01 m/s). A bearing steel ring of AISI 52100 was used as the counterbody. Tests were performed at varying contact pressures, 20, 100, and 140 MPa, and sliding speeds ranging from 0.001 to 1.5 m/s. The wear tracks and debris collected were examined by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD), with the aim of analyzing their morphology and composition. At relatively slow sliding speeds (>0.01 m/s), the specimens exhibited a wear process placed at the mild wear regime, characterized by oxidation and delamination mechanisms of both the aluminum specimen and the steel ring. However, at very slow speed range (<0.01 m/s), an increase in the wear rate and the friction coefficient is observed for all of the aluminum alloys, thus suggesting that an alternative wear mechanism could be taking place.     

Tribological Properties of Double-Glow Plasma Surface Niobizing on Low-Carbon Steel

The niobized layer was formed on Q235 low-carbon steel by double-glow plasma surface niobizing to improve its wear resistance. The microstructure, phase composition, and microhardness were determined. The friction and wear properties of the niobized samples and the untreated alloys were tested on a ball-on-disk tribometer by rubbing against GCr15 and silicon nitride (Si₃N₄) balls at room temperature and 400°C, respectively. The results indicated that the alloyed layer that contained a sediment layer and diffusion layer is about 35 μm in thickness, metallurgically adhered to the base metal. Niobium content was gradually decreased along the depth direction from the surface, which was similar to the change in the microhardness. The alloying layer mainly consisted of Nb, Fe₂Nb, and FeNb phases. Under unlubricated sliding conditions, the friction coefficients and the specific wear rates were lower than those of the untreated carbon steel at room and high temperatures. The wear mechanism of the niobized specimen at room temperature is dominated by slightly abrasive wear, whereas the predominant wear mechanism is abrasive wear and fatigue delamination at high temperature.     

Microstructure and Wear Behavior of a Manganese Bronze Bearing Material under Unlubricated Conditions

In an attempt to collect information about the tribological performance of copper-based bearings, the friction and wear behaviors of C86300 manganese bronze were investigated. The characteristics of the base material were determined by structural and mechanical investigations. Then, dry sliding pin-on-disc wear tests were performed against an AISI 52100 steel counterface. After the wear tests, the worn surfaces of the pins and wear debris were studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy. In addition, light optical microscopy and microhardness measurements were performed for examination of the steel counterfaces and worn pin subsurface layers. With increasing normal load, the wear rate of commercial C86300 alloy (containing 0.6 wt% Si) decreased initially and then began to increase. After reaching a maximum wear rate at the load of about 60 N, the wear rate decreased again with a further increase in the normal load. However, the wear rate of this C86300 alloy mainly decreased with increasing sliding speed. Adhesive and abrasive wear were the dominant wear mechanisms under the designed conditions.     

Monitoring of Wear Characteristics of TiN and TiAlN Coatings at Long Sliding Distances

TiN and TiAlN thin hard coatings have been widely applied on machine components and cutting tools to increase their wear resistance. These coatings have different wear behaviors, and determination of their wear characteristics in high-temperature and high-speed applications has great importance in the selection of suitable coating material to application. In this article, the wear behavior of single-layer TiN and TiAlN coatings was investigated at higher sliding speed and higher sliding distances than those in the literature. The coatings were deposited on AISI D2 cold-worked tool steel substrates using a magnetron sputtering system. The wear tests were performed at a sliding speed of 45 cm/s using a ball-on-disc method, and the wear area was investigated at seven different sliding distances (36–1,416 m). An Al₂O₃ ball was used as the counterpart material. The wear evolution was monitored using a confocal optical microscope and surface profilometer after each sliding test. The coefficient of friction and coefficient of wear were recorded with increasing sliding distance. It was found that the wear rate of the TiAlN coating decreases with sliding distance and it is much lower than that of TiN coating at longer sliding distance. This is due to the Al₂O₃ film formation at high temperature in the contact zone. Both coatings give similar coefficient of friction data during sliding with a slight increase in that of the TiAlN coating at high sliding distances due to the increasing alumina formation. When considering all results, the TiAlN coating is more suitable for hard machining applications.     

Wear Mechanisms in Galling: Cold Work Tool Materials Sliding Against High-strength Carbon Steel Sheets

Transfer and accumulation of adhered sheet material, generally referred to as galling, is the major cause for tool failure in sheet metal forming. In this study, the galling resistances of several tool steels were evaluated against dual-phase high-strength carbon steel using a SOFS tribometer, in which disc-shaped tools were slid against a real sheet surface in dry sliding test conditions. Three different frictional regimes were identified and characterized during sliding, and any transition in friction corresponded to a transition in wear mechanisms of the sheets. The performance of the tools depended on load, material and the particular frictional regime. Best overall performance was obtained by nitrogen-alloyed powder metallurgy tool steel.     

Wear Behavior of Magnesium Alloy AZ91 Hybrid Composite Materials

The influence of hybrid reinforcements including silicon carbide and graphite particles with a size 37–50 μm on the wear characteristics of AZ91 magnesium alloy was studied. The dry sliding wear test was conducted using a pin-on-disc wear testing machine in the load range of 20 to 80 N at different sliding velocities in the range of 1.047 to 2.618 m/s. The results show that the wear resistance of composites was much better than that of the base matrix material under the test conditions. At a speed of 1.047 m/s and load of 40 N, the wear rate (mm³/km) of the unreinforced alloy was 6.3, which reduced to 3.8 in the case of 3% reinforced composite. The antiwear ability of magnesium alloy composite was found to improve substantially with the increase in silicon carbide and graphite content from 1 to 3% by weight and the wear rate was found to decrease considerably. At a speed of 1.047 m/s and load of 80 N, the wear rate (mm³/km) reduced from 11.8 to 9.1 when the reinforcement content increased from 1 to 3%. However in both the unreinforced alloy and reinforced composite, the wear rate increased with the increase in load and sliding velocity. An increase in the applied load increases the wear severity by changing the wear mechanism from abrasion to particle cracking-induced delamination. The worn surface morphologies of the composite containing 3% reinforcement by weight for the sliding velocity of 1.047 m/s were examined using scanning electron microscopy. Different wear mechanisms, namely, abrasion, oxidation, and delamination, have been observed.     

Bio-Fuel-Contaminated Lubricant and Hardening Effects on the Friction and Wear of AISI 1045 Steel

A study has been made on the wear and friction of hardened AISI 1045 steel using a tri-pin-on-disc type of friction and wear apparatus. During the investigation the linear pin wear, coefficient of friction and rise in pin specimen temperature were monitored and wear and friction curves plotted. Wear surfaces and mechanisms were investigated by means of optical microscopy. Analysis of used lubricating oil was performed using FTIR spectroscopy.

It was shown that the wear rate, type of wear and friction coefficient were influenced by contaminating the lubricant with bio-fuel as well as the surface hardening treatment. Corrosive wear and pits on the specimen surface were found when plain bio-fuel was used as lubricating oil. The results also confirmed that better wear resistance was obtained from the surface-hardened steel specimen with 4 % bio-fuel-contaminated lubricant.

Results from this study will be useful in material selection for tribological components in diesel engines running on vegetable fuel.     

Embedding Wear Models into Friction Models

Frictional behavior in dry or boundary-lubricated tribosystems is commonly time-dependent. Examples include phenomena like running-in, scuffing initiation, adhesive transfer, coating wear-through, and lubricant starvation. Fundamental models for the sliding friction coefficient usually focus either on determining a steady–state value or on predicting periodic behavior like stick-slip. They often neglect the details of long- and short-period frictional transients, some of which are quite repeatable. In addition to generating heat, frictional work is known to be dissipated in several ways, including roughness changes, wear particle generation, tribomaterial evolution, and microstructural alteration. Pairs of materials can display identical average friction coefficients but significantly different wear processes because frictional work is dissipated differently from one pair of materials to the next. The attributes of friction-versus-time behavior for combinations of metals, ceramics, and polymers can be comprised of stages whose understanding may require the development of piecewise friction models that include wear. This paper discusses past work on the subject, exemplifies embedding a simple wear model into a friction-versus-time model, and indicates how friction process diagrams can play a role.     

Wear Characteristics of Large Grinding Balls in an SAG Mill

The wear characteristics of larger than 120 mm-diameter grinding balls used in large semiautogenous (SAG) mills is studied in the present paper. SEM observation on the worn ball surface reveals a severe microcutting process. Abrasion grooves can be found on the overall surface. Moreover, persistent microcracks are found on the surface. The observation on the cross section indicates extended white layers and white bands exist in the subsurface of worn balls. The white layer is not homogenous on the surface. The largest white layer is about 20 μm thick and 1.3 mm long. The wear resistance of the white layer is tested with a simulated high stress impact wear tester. It is found that the white layer is associated with delamination wear, which significantly increases the wear rate. The delamination wear mechanism is explained from the intensely deformed microstructure and microcracks inside the white layer. Based on the experimental results, a wear formula consisting of both microcutting wear and delamination wear is submitted. This formula means that high wear resistance is only achieved when the hardness and fracture toughness of grinding balls are increased simultaneously.     

非调质钢35MnVN强化状态滑动磨损特性的铁谱分析

本文应用铁谱技术对非调质钢３５ＭｎＶＮ及调质钢４０Ｃｒ，４５号钢强化状态的磨损过程进行了分析比较，结果表明：在滑动磨损条件下，３５ＭｎＶＮ强化状态的耐磨性优于４０Ｃｒ，４５号钢质后强化态的耐磨性，说明在滑动磨损工况下非调质钢３５ＭｎＶＮ完全可以取代调质钢４０Ｃｒ，４５号钢使用。     

Measurement of Friction Surface and Wear Rate between a Carbon Graphite Brush and a Copper Ring

A pin-on-disc surface friction tester designed by the authors was used to measure the surface friction temperature of a carbon graphite brush sliding against a copper ring under the condition of no flow by electric current. Microelectromechanical systems (MEMS) fabrication techniques including sputtering, lithography, and etching processes were utilized to fabricate metal film temperature sensors on the surface of the carbon graphite brush. The true temperature measurement system of the friction surface of the carbon graphite brush was then established. A USB-DAQ system and LabVIEW software were adopted for the data acquisition/management of analog signals. In this research, the relationship between friction temperature and wear rate was investigated using experiment data. Optical and scanning electron microscope (SEM) images of the friction surface of the carbon graphite brush were taken and analyzed to study the effect of temperature on the friction surface. From this experiment, it was found that the debris of a mixture of brush and copper particles softens under high temperature, adheres to the brush surface, and forms flattened areas. These smooth, flattened areas in turn lower the friction coefficient.     

Wear Behavior of Ceramic Powder and Solid Lubricant Cladding on Carbon Steel Surface

Thick composite coatings of carbides on a metal matrix are ideal for use in components that are subjected to severe abrasive wear. It is a metal matrix composite (MMC) that is reinforced by an appropriate ceramic phase, a solid lubricant coating to reduce friction and to protect the opposing surface. This study tested the wear behavior of a carbon steel surface after cladding by a gas tungsten arc welding (GTAW) method to enhance wear resistance. The microstructures, chemical compositions, and wear characteristics of the cladded surfaces were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The coating was uniform, continuous, and almost defect-free, and particles were evenly distributed throughout the cladding layer. The results of wear tests indicate that the friction coefficient of the TiC coating is lower than that of AISI 1020 carbon steel. Thus, the wear depth of the TiC coating is only one tenth of that exhibited by the AISI 1020 carbon steel. The experiments confirm that the cladding surfaces of TiC particles reduce the wear rate and friction.     

Structure and Micromorphology of Wear Debris of MC Nylon 6 under Dry Sliding: Correlation with Wear Mechanisms

The structure and micromorphology of wear debris of MC nylon 6 under dry sliding were investigated by FTIR, XRD, DSC, and FESEM, and the 3D surface topographies of friction materials before and after the friction test were observed, which will be helpful in understanding the friction and wear processes. The primary crystalline phase of both the unworn MC nylon 6 and the wear debris were α crystal, but the crystallinity of the latter was higher than that of the former. The proportion of α ₂ (002 + 202) planes increased and the reflection from the α ₁ (200) planes was suppressed in the wear debris, indicating a preferential arrangement of α ₂ (002 + 202) on the surface of the wear debris. The transition in structure of the wear debris originated from the activation of the chain segments due to the thermodynamic effects. The thermodynamic effects and high chain segment mobility resulted in the hydrogen bonding whose interchain distance is a larger rupture or even chain scission. MC nylon 6 was severely worn due to the contribution of the tearing force that resulted from the combined action of the tribo-interface adhesion and the shearing effect during friction, whereas no damage happened on the worn surface of the counterpart steel pin even if under severe sliding conditions.