Third-body Layer Research Articles

The impact fretting corrosion behavior and damage mechanism of Inconel 690TT under different impact forces in high temperature pressurized water

The impact fretting corrosion of Inconel 690TT under different impact forces was investigated. The results indicated that there was a competitive relationship between formation of third body layer (TBL) and fragmentation of TBL caused by impact force. With the increase of impact forces, damage mechanism changed from adhesive wear to delamination wear, and crack initiation sites gradually shifted from TBL to internal oxidation zone in tribologically transformed structure (TTS) layer. Nanocrystalline boundaries and defects induced by impact force provided channels for internal oxidation. The formation mechanism of TTS was the combined effect of continuous dynamic recrystallization (cDRX) and twin-assisted cDRX.

Evolution of fretting wear behavior of zirconium alloy cladding tube under gross slip regime in simulated primary water of pressurized water reactor

The evolution of fretting wear behavior of zirconium alloy cladding tubes mated with dimples under the gross slip regime (GSR) was investigated. The findings revealed that the primary wear mechanisms under GSR were delamination, surface fatigue wear and abrasive wear, and the fretting damage rate mainly depends on delamination. The cross-sectional microstructure of the worn area could be divided into the third-body layer, tribologically transformed structure layer, and general deformation layer, with their formation mechanisms analyzed. Furthermore, the mechanism of wear-induced grain refinement was identified as dynamic recrystallization (DRX), including both continuous DRX and discontinuous DRX. Additionally, the processes of fretting wear and DRX were discussed.

The crack initiation mechanism of steel disc when paired with Fe-PM pad for high-speed train braking

In this study, the Fe-based powder metallurgy (Fe-PM) brake pad was paired with a cast steel brake disc to conduct braking tests on a full-scale flywheel braking dynamometer. We systematically analyzed the morphologies of the worn surfaces and the disc temperatures during braking, uncovering the friction and wear characteristics of the friction pair. As well as highlighted the changes in contact status between the friction pair throughout the braking process, which further affected the pad wear rate and thermal fatigue damage to the brake disc. The wear rate of the pad was 0.16 cm3/MJ during the braking tests at an initial brake speed (IBS) of 250 km/h. However, it rapidly increased to 0.66 cm3/MJ as the IBS rose to 380 km/h, indicating a severe decline in wear resistance as the speed increased. The curves of the instantaneous coefficient of friction (COF) displayed significant fluctuations throughout the single braking process and got more pronounced with the increase in the IBS, similar phenomena also occurred on the measured temperature during each braking test. These were caused by the constant changing of the contact status arose by dynamic equilibrium of the formation, spalling, and regeneration for the third body layer (TBL) on the contact surfaces. Additionally, the changing of the contact status also resulted in an uneven distribution of temperature on the disc surface, which in turn generated a temperature gradient and thermal stress. Concurrently, as the braking continued, high frequency alternating thermal stress (HFATS) on the disc surface was induced by the continuously changing contact status, which was confirmed by finite element method (FEM) simulation. As a result, the brake disc would undergo thermal fatigue after fewer braking cycles, and thermal cracks would appear on the disc surface.

Modelling the adhesion enhancement induced by sand particle breakage at the wheel-rail interface

The adhesion at the wheel-rail contact is critical in train operation. Low adhesion leads to a longer distance for a train to accelerate and brake, and this may cause serious accidents. Sand particles are applied onboard trains at the wheel-rail contact to enhance the adhesion level. In this study, a finite element model is developed to investigate the mechanical behaviour of sand particles in a wheel-rail contact and how they affect the adhesion level. The acceleration and braking events using rolling/slipping and sliding contacts are simulated. Morphological properties of sand particles such as size and aspect ratio are considered. The adhesion enhancement is quantified from each simulation for comparison. The results indicate that the adhesion enhancement during the first contact between the wheel and sand particles is negligible and starts to increase when the wheel is rolling on the fragments. Its magnitude is controlled by the new third-body layers generated during the particle breakage under both rolling and sliding contacts. However, under sliding contact, when a similar amount of fragments is considered, the coarser particles with a larger aspect ratio tend to produce a higher adhesion enhancement.

Investigation of rail damage considering impact at a welded joint under wet condition

PurposeThe purpose of this study is to develop a transient wheel–rail rolling contact model to primarily investigate the rail damage under wet condition when the train passes through the welded joints.Design/methodology/approachThe impact force induced by welded joints is obtained through vehicle–track coupling dynamics. The normal and tangential wheel–rail contact pressures were solved by elastohydrodynamic lubrication (EHL) theory and simplified third-body layer theory, respectively. Then, the obtained tangential pressure and normal pressure were applied to the finite element model as moving loads, simulating cyclic loading. Finally, the shakedown map and critical plane method were used to predict rolling contact fatigue (RCF) and the initiation of fatigue cracks.FindingsThe results indicate that RCF will occur and fatigue cracks are more prone to appear on the subsurface of the rail, specifically around 2.7 mm below the rail surface in the vicinity of the welded joint and its heat-affected zone.Originality/valueThe cosimulation of numerical model and finite element model was implemented. The influence of surface roughness and fluids was considered. In this model, the normal and tangential wheel–rail contact pressure, the stress and strain and the rail fatigue cracks were obtained under a rail-welded joint excitation.

Effects of thermal cycling treatment on load bearing and friction behavior of SiCp/A356 composites

During bench tests and actual service, the Al-MMC (metal matrix composite) brake discs used in urban rail transit vehicles experienced problems such as poor wear resistance, compromising the brake discs' stability and safety. While braking, the brake disc material will bear the thermal cycling loads, leading to a certain degree of degradation in the material's performance. In this study, the degradation of the material's performance by the thermal cycling treatment was investigated. The results showed that all material performance degraded to some extent after thermal cycling treatment, with a strong correlation with cycling temperature. The degradation of material performance was caused by a combination of matrix mechanical damage and interface damage. At the same time, the tribological performance of the material also decreased to some extent. The main effect of thermal cycling treatment on tribological performance was its effect on material performance. The increase of hard particles in the abrasive debris resulting from the mechanical damage of the material and the aggravation of the dynamic changes in the TBL (third body layer) were the basic reasons for the surface scratches. The results further help to explore the application of Al-MMCs in high-temperature and long-term service.

Electrochemical study on the fretting corrosion synergistic damage mechanism of Inconel 690 alloy in different dissolved oxygen solution

In-situ electrochemical measurement was used to investigate the fretting corrosion synergistic damage mechanism of Inconel 690 alloy in the solution with different dissolved oxygen (DO) concentrations. The synergistic mechanism of fretting corrosion was quantified. Results show that the minimum fretting corrosion damage of Inconel 690 was obtained at DO concentration of 2 ppm and the corrosion-accelerated wear, which can be represented by the influence of third body layer (TBL) on the fretting corrosion damage mechanism, is the key contributor. The formation and rupture of TBL have been observed under different DO concentrations. In transitional stages of TBL formation and the stage where uniform morphology formed, the TBL with excellent ductility can improve the contact behavior and reduce fretting corrosion damage. In stages during which TBL breaks into hard spinel oxides, severe abrasive wear and fretting corrosion damage will be caused.

Role of Minimum Adhesive Wear Particle Size in Third-Body Layer Properties

We employ a novel discrete element method (DEM) force formulation to simulate adhesive wear and assess the effects of material and loading parameters on the properties of the third-body layer (TBL) formed during sliding motion. The study emphasizes the role of a material’s critical length scale d^{*} in the rheology of the TBL. This critical length scale is already known for controlling the size of smallest wear particles. We observe the emergence of a several wear regimes involving wear particle creation and aggregation, with limited effect from d^{*} on TBL properties. Instead, material strength and surface energy have a profound influence. This study opens up new avenues for exploration of larger systems, three-dimensional setups, and other loading conditions.

Fretting wear behavior of Zr alloy cladding tube mated with Zr alloy dimple under mixed fretting regime in simulated primary water of PWR

The fretting wear behavior of Zr alloy cladding tube under mixed fretting regime in a high-temperature pressurized water was investigated. The main wear mechanism is adhesive wear, with characters of small-scale delamination at the center of worn area and serious delamination on the worn edge. A long crack throughout the worn area and other cracks propagated towards the substrate are observed. The cross-sectional microstructure of worn area can be divided into a thick third-body layer, thin inner oxide layer and thick tribologically transformed structure layer, and their formation mechanisms are analyzed in detail. Finally, the mixed fretting regime process and the microstructural evolution during fretting wear are discussed.

Heterogeneity in tribologically transformed structure (TTS) of Ti–6Al–4V under fretting

Fretting wear is a surface degradation process caused by oscillatory motion and contact slipping. During gross slip, high local stresses and plastic deformation in the surface and subsurface can lead to the creation of a nanosized grained structure called Tribologically Transformed Structure (TTS). The current paper studies the formation of TTS in an alpha-beta Ti–6Al–4V alloy under fretting loading while changing the contact pressure and the number of fretting cycles.Cross-sections of wear scars are observed after polishing and chemical etching. Above a threshold pressure of 300 MPa, TTS appears early in the contact (before 1000 cycles) along with two other structures: a Third Body Layer (TBL) made of compacted debris and a General Deformed Layer (GDL) which is the plastic zone under the TTS. TTS first appears as islands and merges in the middle of the contact after enough cycles. Below 200 MPa, only TBL and GDL are formed. At 200 MPa, only small, localized TTS is found. All structures have the same chemical compositions as the initial bulk material except for the nitrided TBL. TTS has a very high hardness compared to the bulk. TTS was carefully extracted using a Focused Ion Beam (FIB) and its microstructure was observed with a Transmission Electron Microscope (TEM). It shows extreme grain refinement and is composed of two alternated zones. The first zone I is composed of α grains with a size of 20–50 nm with crystallographic texture. Zone II comprises nanosized equiaxed grains whose sizes range from 5 to 20 nm without texture. The results made it possible to establish a scenario of the appearance of the TTS according to the conditions of contact pressure and number of fretting cycles.

PHYSICOCHEMICAL ASPECTS OF THE WORK OF PASSENGER CAR BRAKE LININGS. PART II THE EFFECT OF LUBRICATING ADDITIVES

The paper presents the influence of various systems of lubricating additives which determine the performance of the friction materials of brake linings. The base hybrid friction material formulation was modified with various types of lubricating additives. These additives are divided into groups containing commonly used lubricating materials: carbons and sulphides, compounded in various proportions, influencing the formation and structure of the so-called third body layer (TBL) on the surface of the brake disc because of braking. Raman Spectroscopy (RS), time of flight Secondary Ion Mass Spectroscopy (ToF-SIMS) and high-resolution scanning electron microscopy with an X-ray analyser (SEM-EDS) equipped with a focus ion beam (FIB) were used for chemical and morphological analysis of the surface layer of brake disc after breaking tests. The results of the physicochemical analysis of TBL were correlated with the results of tribological tests (according to the SAE-J2522 procedure, commonly known as AK-Master) on a brake dynamometer adapted to the measurements of acoustic signals (NVH – noise, vibration, and harshness). The obtained results confirm the important role played by the so-called third body layer, formed on the surface of the brake disc for safety (COF), durability (wear of friction elements) and the acoustic spectrum accompanying braking.

Tribological behavior and wear mechanism of C/C–SiC brake discs based on third‐body layer

AbstractC/C–SiC composites are promising candidates for heavy‐duty tracked vehicle brake discs. A third‐body layer (TBL) can be formed on the surface of C/C–SiC self‐mated brake discs, which has an important impact on tribological behavior and wear mechanism of brake discs. Herein, the formation conditions and evolution process of TBL and its effect on friction and wear properties were investigated. An appropriate braking pressure and speed (P and V) are beneficial to the cutting of asperities and refinement of wear debris on the contact surface, which are preconditions for the formation of original TBL. The original TBL can be formed under the P·V of 12, 15, and 16, which effectively improve braking stability and reduce the wear rate. During the continuous braking process, the original TBL undergoes growth, stabilization, destruction, and regeneration. Under the frictional heat and compressive stress, wear debris gradually evolves into a uniform and dense TBL. The average coefficient of friction and wear rate reach to the lowest value of .446 and 38.5 × 10−3 cm3/MJ, respectively. A continuous high temperature in the later stages of braking leads to severe oxidative wear. The newly formed TBL covers the original surface to form a multilayered structure, indicating the TBL undergoes destruction and regeneration.

Fretting corrosion-induced microstructural evolution of Alloy 690TT tube in high temperature pressurised water

The friction-induced microstructural evolution of Alloy 690TT tubes submerged in a high temperature pressurised water was investigated. Two typical local regions characterised by significantly different worn morphologies (resulting from the stress field and material couple) were investigated in detail. A thin third-body layer and a thick Fe-rich layer were observed and their oxidation behaviour was analysed. Moreover, the main oxide was spinel, whereas the amorphous band was only observed in the Fe-rich layer. The tribologically transformed structure is formed by the mechanism of discontinuous dynamic recrystallisation. Finally, the microstructural evolution of the two areas during fretting corrosion is discussed.

Fretting wear behaviour of Zr alloy cladding tube under partial slip regime with different duration in simulated primary water of PWR

The fretting wear behaviour of Zr alloy cladding tubes under partial slip regime in a high temperature pressurised water was investigated. The fretting regime remained unchanged with the increasing fretting time and hence both the wear volume and depth of the worn scars formed on Zr cladding tubes changed slightly. The wear mechanism was delamination at some local regions, resulting in a slight damage. Third-body layer, oxide layer, tribologically transformed structure layer, and general deformation layer were observed form the cross-section of the worn scar and their formation mechanisms were analysed in detail. Moreover, from the metal/oxide interface to surface, the main oxide transitioned from tetragonal-ZrO2 to monoclinic-ZrO2. Finally, the partial slip regime process and the microstructural evolution during fretting wear were discussed.

Effect of the cycle number on fretting wear behavior of alloy 690TT tube in high-temperature pressurized water

In high temperature water, the fretting wear behavior of Alloy 690TT against Type 405 stainless steel were investigated under different cycle numbers. Results indicated that the change of wear coefficient strongly depended on wear stage and oxide type of compact third body layer (TBL). Within 100000 cycles, the wear gradually entered the stable wear stage from the running-in stage, and the wear coefficient changed conformed to power law distribution. When the number of cycles exceeded 100000, a smooth and compact TBL composing of Fe2O3 and spinel oxide was formed on the surface of the wear scar, the wear coefficient changed slowly. With the increase of cycle number, the percentage of NiCr2O4 and NiFe2O4 in the surface oxide gradually decreased, while that of Fe2O3 gradually increased. The formation of cracks parallel to the surface was related to the surface stress field distribution. During the fretting process, the state of the stress component parallel to the surface changed from tension to compression, prevented cracks from moving to the matrix deep expansion, resulting in the crack propagation direction parallel to the wear surface in the TBL. Finally, the relationship between stable wear life and critical wear depth was established, and the stable wear life was related to running-in wear volume (V0) and stable wear rate (γa).

The formation and evolution of third body covered on 690 alloy tube during fretting in 285 ℃ air

The fretting wear tests of 690 alloy tube/405 stainless steel plate under various fretting cycles have been conducted in 285 ℃ air using a self-designed elevated-temperature fretting wear rig. The results demonstrated that the formation of third body layer (TBL) had considerable influence on the fretting wear performances of 690 alloy tube. The presence of TBL between the interfaces protected the partial 690 alloy tube surface from being damaged. Consequently, it resulted in the discontinuity of wear scar and reduction of coefficient of friction (COF) after approximately 500th cycles. Along the thickness of TBL, the contents of oxygen, chromium and iron took on obvious stratification induced by alternating the transfer layer and oxidation layer.

Influence of non-dry condition creep curves in switch negotiation

In the benchmark on switches and crossings, simulations have been carried out in different switch configurations and operational conditions, with a specified wheel/rail friction coefficient of considered as dry friction. This means that contamination or third-body layers are not taken into consideration, thus using a theoretical creep curve that is much steeper than the actual curves measured in real railways. In this paper, we perform a comparison between theoretical and measured creep curves and then estimate the impact on simulated creep forces when measured creep curves are used instead of theoretical ones.

Fretting wear modeling of 3D and 2D Hertzian contacts with a third-body layer using a Winkler elastic foundation model

This article aims at modeling fretting wear in a 2D cylinder-on-flat contact using Winkler elastic foundation model (WK). This model is compared with existing FEM and semi-analytic approaches as well as with experiments where the potentials and limits of the latter are carefully discussed. Following this, WK approach is extended to a 3D sphere-on-flat contact where the results showed that this approach captures nicely the 3D experimental wear profile with lower computation costs compared to semi-analytic approach. Finally, WK approach is applied for more complex cases as reciprocating sliding and fretting wear incorporating a third body layer in both 2D and 3D configurations. Interesting results were obtained confirming the potential of this approach to model complex sliding and geometrical conditions.

Effect of the third body layer formed at different temperature on fretting wear behavior of 316 stainless steel in the composite fretting motion of slip and impact

316 SS is a commonly used material for steam generator tube. The object of this investigation is to study the influence of temperature, which is 95 °C and 250 °C, on the formation of the third body layer (TBL), and the role of TBL on the fretting wear behavior of 316 SS. Thus, the fretting wear experiment between 316 SS tube and 316 SS plate was carried out in the composite fretting motion of slip and impact in pure water environment. The experiment time was set as 24 h, 48 h, 72 h and 120 h. The results show that at 95 °C, TBL is hard and attaches closely to the surface, which can lead to uniform abrasion and result severe microploughing between the base materials. While at 250 °C, the existence of thick TBL can avoid direct contact between base materials, and it can be easily deformed by shear forces due to its ductility, which acts as a lubricant and reducing volume loss and wear coefficient. Finally, we can conclude that temperature affects the formation mechanism and properties of TBL, thus changing the fretting wear behavior.

Microstructure and tribological behaviors of diffusion bonded powder sintered Cu–Sn based alloys

Owing to good self-lubricating performance, tin bronze is widely used in industrial fields. As tin bronze parts manufactured by powder metallurgy, their tribological performances are influenced by raw powder. In this work, four types of self-lubricating copper alloy composites (CuSn10 (D), CuSn10, CuSn10Pb10 (D) and CuSn10Pb10) were prepared by sintering completely alloyed powder and diffusion alloyed copper tin powder. The morphology, element distribution and microstructure of raw powder and their sintered Cu alloy composites were observed. The tribological properties of Cu alloys were investigated by block-ring friction test under different working conditions and their worn surface and wear debris were analyzed. The results show that the diffusion alloyed powder has an irregular dendritic morphology and its sintered Cu alloy is more likely to produce twin structure which enhances the hardness and the bearing capacity of the material. Compared with completely alloyed powder sintered CuSn10 sample, the wear rate of CuSn10 (D) sintered from diffusion alloyed powder was reduced by 83.96%, 74.39%, and 67.63% under three typical working conditions. Under dry friction conditions, the wear rate of CuSn10 (D) is reduced by 63.64% than CuSn10, and CuSn10Pb10 (D) is 25% lower than CuSn10Pb10. The investigation on the wear tracks and wear debris of Cu alloy composites showed that the diffusion alloyed powder sintered samples are inclined to form a more consecutive and integral third-body layer on wear tracks and which contributes to the better wear resistance.