Cast Iron Disc Research Articles

Pin-on-disc study of a friction material dry sliding against HVOF coated discs at room temperature and 300 °C

The tribological behavior of a commercial semi-metallic friction material dry sliding against an uncoated cast iron disc and HVOF coated discs at room temperature and at 300 °C has been investigated. Two types of coatings were investigated, based on Cr3C2-NiCr and WC-CoCr systems. The tests were carried out using a pin-on-disc apparatus. The characteristics of the friction layer that forms on the worn surfaces of the friction material (the pin) and on the counterface disc were analyzed and correlated with the friction and wear behavior of the couplings. At room temperature, quite a long initial stage was observed, required to form a compact friction layer and to achieve a constant average friction coefficient. At 300 °C, steady-state conditions are attained almost from the beginning of the test. The wear rates of the friction materials are mild at room temperature and close to severe at 300 °C because of the thermal softening of the friction material. The wear rates of the coated discs are always negligible, since the contact temperature is not sufficiently high to induce a softening or an oxidative damage of the coatings. Although referring to rather simplified testing conditions, the results obtained in this study provide useful indications on the possibility of using HVOF coatings in braking systems to reduce not only their wear but also, most importantly, the release of particulate matter in the environment.

Dry friction behavior of NiCrBSi-%35W2C coated brake disks

Abstract For speeding up motor vehicles, new brake disk materials with higher frictional need to be developed. Brake disks work under very difficult thermomechanical conditions due to high temperature and wear. As most of commercial disks have high wear rate and low braking performance, there is a need for development and manufacturing of new disks-brake linings to reduce wear and to increase braking performance in motor vehicles. Ceramic coated disks have shown good stability in friction coefficient at a high speed and high energy braking conditions. Therefore, flame spraying technique for cermet coating materials has been chosen as a good method to produce coatings on a metallic substrate. In this study, a sample cast iron disk with ventilation channels coated with NiCrBSi-%35W2C powder by the flame spraying method were investigated. The braking performances of uncoated disk and coated disk were tested according to SAE J2430 test standard. It was found out that the coated disk had lower surface roughness and higher coefficient of friction than the uncoated disk. The NiCrBSi-%35W2C coated disk exhibited less wear, a higher coefficient of friction and longer life than the uncoated disk. As a result, the NiCrBSi-%35W2C coated disk could be a much better alternative for a new generation of brake disks in the motor vehicles than the uncoated disk.

Determination of the maximum temperature at single braking from the FE solution of heat dynamics of friction and wear system of equations

ABSTRACTA system of equations of heat dynamics of friction and wear (HDFW) for a pad–disc tribosystem during a single braking has been formulated. It takes into account the coefficient of friction dependent on the maximum temperature, which is the sum of the mean temperature of the nominal contact region (the macro contact) and the flash temperature on the real contact area (the micro contact), temperature-dependent properties of materials and wear. Numerical solution of the initial problem of motion and the nonlinear boundary-value heat conduction problem was obtained. Computations were performed using the axisymmetric FE contact model for the metal ceramic pad and the cast-iron disc.

Dry sliding of a low steel friction material against cast iron at different loads: Characterization of the friction layer and wear debris

Pin-on-disc testing was used to investigate the sliding behavior and the wear products of a low-steel friction material against a cast iron disc at different applied loads, to investigate the effect of the temperature rise induced by frictional heating. The testing rig was operated in a clean chamber with a purified incoming air flux. The outgoing flux carries the wear particles to an impactor that counted and sorted them by average diameter and weight. At increasing applied loads, corresponding to a proportional increase of the pin-disc contact temperature, the coverage of both the pin and disc surface by a friction layer was found to increase too. The relevant X-Ray diffraction patterns revealed the presence of a large amount of graphite and different compounds originating from the friction material and from the counterface disc, mainly iron oxides, as concerns this latter. After the test at the lowest investigated load, i.e., 1kg, the disc worn surface exhibited abrasive grooves and a discontinuous friction layer mainly made of compacted iron oxide particles. After the test at higher loads, i.e., 5 and 7kg, the disc surface was covered by a compact friction layer. As concerns the friction layer on the pins, most of the ingredients from the friction material were detected, in association with the iron oxides from the disc. These results can be interpreted in terms of the temperature stability range of the phenolic resin used as a binder of the friction material. The characterization of the collected airborne wear debris showed that the particles produced by the low temperature (i.e., low load) test were mostly equiaxed; whereas those produced by the high temperature (i.e., high loads) tests, predominantly displayed a plate-like morphology. The mechanisms of their formation in relation to the characteristics of the friction layers are illustrated and discussed.

Influence of nano-potassium titanate particles on the performance of NAO brake-pads

The present era is dominated by nano-materials. Researchers are keen to explore the potential of nano-particles (NPs) in composites because of their intensive interaction with the matrix and surfaces due to very large surface area.Potassium titanate (KT) is used as a filler in a good quality non-asbestos organic (NAO) friction materials (FMs). Based on a little information available in the literature, it is claimed to reduce friction-fluctuations, fade and wear. However, exact role of KT in FMs is not so clear due to contradictory findings. Interestingly, no paper is available on exploration of NPs of KT in FMs.Keeping this in view, two realistic multi-ingredient NAO FMs in the form of brake-pads with identical compositions but differing in size of a theme ingredient, KT were developed. One composite was without KT (K0), while two composites containing 3% micro and 3% nano-KT particles were designated as KM and KN. These were characterized for physical, mechanical and tribological performance. Initial tribo-evaluation of composites was done on a reduced scale prototype (RSP) under various operating conditions. Final tribo-performance was evaluated on a full scale brake dynamometer following JASO C 406 Schedule using gray cast iron disc. Various performance parameters such as performance µ, fade µ, recovery µ; fade ratio, recovery ratio, wear resistance etc. were used to evaluate the performance of FMs.Both testing data (prototype and realistic machine) showed that almost all performance parameters were significantly and beneficially affected due to NPs of KT. Nano-KT particles proved to improve performance µ and wear resistance significantly compared to its micro-partner. Worn surface analysis of pads and discs was done to understand wear mechanism by SEM and EDAX technique. It was finally concluded that Nano-KT particles have a potential to enhance performance of FMs significantly.

Sliding wear behaviour of Al-Si alloy–fly ash composites produced by powder metallurgy technique

PurposeMetal matrix composites (MMCs) are commonly used in many aerospace and industrial applications. MMCs possess significantly improved properties including high specific strength, specific modulus, damping capacity and good wear resistance compared to unreinforced alloys. The purpose of this paper is to describe the tribological studies of Al-Si alloy–fly ash composites manufactured using powder metallurgy technique.Design/methodology/approachAl-Si (12 Wt.%) alloy–fly ash composites were developed using powder metallurgy technique. Al-Si alloy powder was used as matrix material, and the fly ash was used as reinforcement. The particle size of Al-Si alloy powder was in the range of 75-300 μm, and the fly ash was in the range of 1-15 μm. The friction and wear characteristics of the composites were studied using a pin-on-disc set up. The test specimen was mated against cast iron disc, and the tests were conducted with the loads of 10, 20 and 30 N, sliding speeds of 0.5, 1 and 1.5 m/s for a sliding distance of 2,000 m.FindingsThe effects of load and sliding speed on tribological properties of the base alloy and Al-Si alloy–fly ash composites pins on sliding with cast iron disc are evaluated. The wear rate of Al-Si alloy–fly ash composites is lower than that of base alloy, and it increases with increasing load and sliding speed. The coefficient of friction of Al-Si alloy–fly ash composites is increased as compared with base alloy.Practical implicationsThe development of Al-Si alloy–fly ash composites produced by powder metallurgy technique will modernize the automobile and other industries because near net shape at low cost and good mechanical properties are obtained.Originality/valueThere are few papers available on the development and tribological studies of Al-Si alloy–fly ash composites produced by powder metallurgy technique.

H-BN lamellar lubricant in hydrocarbon and formulated oil in porous sintered bearings (iron + h-BN)

We investigate the frictional performance of the hexagonal boron (h-BN) nitride, sintered into the porous iron bearing, with the lubricating hydrocarbon and formulated oils. It was established that the h-BN particles largely improved the tribological performance of the surfaces under contact between the porous bearing and a grey cast iron disc. The h-BN particles (platelets) released during wear reduces friction in a surfactant-free (no additive) lubrication. The hexagonal h-BN solid particles are able to form efficient friction-reducing lamellar sheets on the contacting surfaces. It was found that solubilization of h-BN particles by reverse micelles were not beneficial in reducing friction in lubrication with surfactant. The role played by the surfactant and its effect on h-BN particles lubrication were discussed with respect to reverse micelle and solubilization concepts.

Thermostressed state of a pad–disk tribosystem during single braking

The temperature and stress distributions in a disk under single braking have been studied. The finite-element method (FEM) has been used to obtain a numerical solution to the heat-conduction boundary problem for a steadily decelerated rotating disk heated in a local area of the working surface by a frictional heat flow. Given the temperature field, the finite-element method has been used to solve the corresponding quasistatic thermoelasticity boundary problem. The elastostatic boundary problem has been numerically solved separately for a disk loaded with distributed normal and shear stresses in the contact area. The complete field of stresses in the disk has been determined by adding up elastic and thermoelastic components. Numerical analysis has been performed for a cerametallic (FMC-11) pad—cast-iron (ChNMKh) disk friction couple.

Effect of roughness on the wear behavior of HVOF coatings dry sliding against a friction material

WC-CoCr coatings on cast iron discs were prepared with different surface roughness and submitted to dry sliding wear tests against a commercial friction material using a pin-on-disc configuration. The effect of roughness on the friction and wear of the tribological system was evaluated. The pin wear rate increases with the coating roughness and becomes very high for an arithmetic average roughness, Ra, in excess of 1 μm. In contrast, the friction coefficient was found to increase as roughness decreased. The discs wear was anyway negligible. The experimental results were explained considering the characteristics of the friction layer that forms during sliding at the interface of the mating bodies in dependence of the initial roughness of the coatings. It is shown that the friction layer plays an important role in determining the relative contribution of the abrasive and adhesive interactions and, thereby, the resulting friction and wear behavior of the tribological system.

Effect of Rockwool and Steel fiber on the Friction Performance of Brake Lining Materials

Wear resistance and Frictional stability are key performance requirements for brake lining. Automotive brake linings are usually made of various ingredients such as binder, filler, friction modifiers and reinforcement. Rockwool is a mineral fiber and steel fiber is a metallic fiber. In this work reinforcement fibers used are both the mineral and metallic fibers with six different composition prepared and tested. The result shows that metallic fibers should be high compared to mineral fiber for best frictional performance and wear resistance. Friction-wear properties of the reinforced samples were investigated on the cast iron disc as a counterpart using a pin on disc wear tester. The investigation confirmed that the sample with increase in steel fiber (4%, 8% and 12%) improves the wear resistance. On the other hand specimen with high content of Rockwool fiber forms an improper ratio among the other ingredients. The SEM images of the sample indicated that an increase in steel fiber higher than 12% content resulted in adhesive wear.Analysis of the experimental result shows that the sample with 12% steel fiber and 8% Rockwool fiber exhibited the optimum friction-wear behavior. Finally the effect of environment on the composites was investigated in water, salt water and oil.

Effect of convective cooling on temperature and thermal stresses in disk during repeated intermittent braking

A numerical solution of the heat-friction problem for a brake pad–brake disk system during repeated intermittent braking has been obtained using the finite-element method. The obtained temperature field has been used to study the thermal stress state of the disk. A numerical analysis has been carried out for a metal-ceramic pad–cast iron disk friction pair during ten intermittent brakings. The effect of the coefficient of the coefficient of heat transfer on the temperature, the stress tensor components, and the Huber–Mises–Henky stresses on the working surface of the disk has been investigated.

Morphological analysis of pad–disc system during braking operations

A method has been developed for quantifying the percentage of friction layer coverage on a brake disc surface. The method is used to examine the relationship of layer coverage to the coefficient of friction and the morphology of the contact plateaus existing on the brake pad surface. Two kinds of brake pads, a non asbestos organic (NAO) and a semi-metallic (SM), were subjected to sliding against a gray cast iron disc in a laboratory-scaled tribometer. In order to observe the effect caused by the contact pressure on the measured parameters, tests were carried out with two normal forces (600N and 1200N). Micrographs of brake discs and pads were obtained as the tests progressed. MatLab (Mathworks®) scripts were developed to process the images of the brake disc and pad. Using these, the number and the area fraction of contact plateaus were investigated. Both the NAO and the SM materials formed a heterogeneous friction layer on the disc surface, but SM material produced a more uniform distribution of the friction layer. An increase in the normal force led to an increase in the friction layer deposited on the brake disc surface for the NAO; however, the opposite was observed for the SM material, that is, an increase in the normal force tended to remove the friction layer on the brake disc surface. Correlations among friction, friction layer coverage, temperature variation and morphology parameters are discussed.

Humidity and Water Effect on Wear Characteristics of Disc Braking System

A series of wet braking tests has been performed using two different pad materials. Brake tests were conducted in different operating conditions i.e. dry, humid air and wet environment in which both pad samples were tested against grey cast iron disc at certain sliding speed and contact pressure. Wear analysis was performed to find correlation between presence of water and changes in brake pad wear characteristics. The results revealed that regardless of the frictional behaviour, wear rate for both pad materials tested at humid air and wet braking is significantly lower than in dry results.

Mutual influence of the sliding velocity and temperature in frictional heating of the thermally nonlinear disc brake

Transient temperature fields in sliding components of a disc brake at coupling of temperature-dependent coefficient of friction, thermophysical properties of materials, time-dependent contact pressure and a velocity were analysed using the finite element method (FEM). Simulation of a single braking process for a cast-iron disc (ChNMKh) and a pad made of FMC-11 at four values of the contact pressure was carried out. Dependencies of the coefficient of friction and thermophysical properties of materials were adopted from experimental data. The temperature fields, braking times, and braking distances were calculated and confronted with the cases at the constant coefficient of friction.

Precision Machining of Wear-Resisting Friction Parts’ Plane Surfaces from New Composite Materials Based on High Alloy Steels for Technological Complexes

Background . Researches of fine processes of precision machining of wear-resisting friction parts’ plane surfaces from new composite materials based on die and instrumental steel wastes for technological complexes of printing machine building enterprises and also for machine tool systems of light and food industries of national economy of Ukraine were presented in the article. O bjective . The purpose of this paper is to determine the quality parameters of precision machining with such new composite materials as 85Х6НФТ, 11Р3АМ3Ф, Р6М5К5, Р6М5Ф3, 4ХМФТС, 4Х2В5МФ and also to determine the effect of technological processing parameters on quality indexes of treated surfaces. M ethods . Fine processes of precision machining of friction parts’ plane surfaces were carried out with C-15 machine tool. Disc material for fine machining is cast iron. As abrasive finishing micropowder s were used grains of white chrome electrocorund with the percentage composition of chromium oxide from 1.0 to 2 % (32A), titanium electrocorund with the percentage composition of titanium oxide from 1.5–2 % (37A), borazon (BN) and artificial diamond (AC). Granulosity of abrasive powders for fine machining is 1–14 μm. Composition of lubricating cooling liquid was mixture of kerosene (70 %) and industrial oil U16 (30 %). R esults . It was demonstrated the technological factors of fine precision machining development such as cutting parameters, material and granulosity of abrasive powders for fine machining and also composition of lubricating cooling liquid essentially influence the quality of surface’s parameters of researched parts. The best results were obtained when using cast iron discs for finishing precision machining development, grains of artificial diamond (AC), borazon (BN) and white chrome electrocorund with the percentage composition of chrome oxide from 1.0 to 2 % (32A) with granularity 1–14 μm and at the same time with use of kerosene (70 %) + industrial oil U16 (30 %) mixture. C onclusions . For the first time it was shown the main regularities of fine precision machining parts’ plane surfaces from new composite materials based on stamp and die steel wastes meet fundamental regulations of super fine abrasive grinding in general theory. The recommendations for choice of cutting parameters for different technological purpose that are manufactured from composite alloys based on stamp and instrumental steels wastes are developed.

Wear behavior of a low metallic friction material dry sliding against a cast iron disc: Role of the heat-treatment of the disc

In commercial automotive braking systems, consisting of a friction pad dry sliding against a pearlitic cast iron disc, the wear of the disc contributes significantly to the overall wear. In the present work, pin-on-disc sliding tests were carried out for determining the role of conventional heat-treatment conducted on cast iron discs on the friction and wear behavior of the above coupling. Wear rates of both disc and friction materials were reduced by almost one order of magnitude when the disc is preliminarily heat-treated and then ground to remove the surface decarburized layer that forms during the thermal cycle. Heat-treatment and heat-treatment plus grinding resulted also in the decrease of the friction coefficient, which was comparatively lower for the ground samples. The friction and wear behavior along with the contact temperature evolutions were rationalized according to the actual materials characteristics, as resulting from the different treatments.

Tribological Behavior of B4C/hBN Ceramic Composites Sliding Against Gray Cast Irons Without Lubrication

Based on hot-pressing sintering, boron carbide/boron nitride (B4C/hBN) ceramic composites were prepared as pin samples to slide against gray cast iron disks (GCI) in the air on a pin-on-disk tribometer. In the study, we investigated the influence of hBN mass fraction and test load on the tribological performance. The morphology features of friction surfaces were observed with scanning electron microscope. The compositions of friction surfaces and wear debris were analyzed by X-ray photoelectron spectroscopy and X-ray diffraction. Our results show that in the case of 5 N load, the friction coefficients of B4C/hBN (hBN content of 0, 10 % weight ratio, named as BN00, BN10) ceramic composites coupled with GCI were reached up to 0.5. However, as hBN contents reach to 20 and 30 % (BN20, BN30), the friction coefficient was reduced to 0.2. The tribological mechanism of GCI-BN00 couple is mainly based on adhesive wear with severe plastic deformation of GCI disk. On the contrary, a continuous surface film is promoted on the worn-surface BN30. Thus, the main tribological morphology of the coupled gray cast iron shows slight micro-cuttings. With an increase in the test load, the wear mechanism of GCI-BN00 and GCI-BN10 is still adhesive wear with similar friction coefficients compared to 5 N load. However, as test load increases, the film formed on BN30 worn surface is damaged, resulting in the rise of the friction coefficient. The friction coefficient increases to 0.6 at the load of 10 N, indicating that the addition of hBN has no improvement on lubrication in this load regime.

Effect of dimensions of pad and disk on the temperature and duration of braking

A solution to the axisymmetric nonstationary thermal problem of friction for a disk–pad tribosystem has been obtained using the finite element method taking into account the interrelation between the temperature and velocity of sliding in the course of braking. The calculations are carried out for an FMK-11 ceramics pad and a ChNMKh cast iron disk at the coefficient of friction that depends on the temperature. The effect of the dimensions of the pad and disk on the temperature and duration of braking is studied provided that the volumes of the pad and disk remain unchanged.

An Oil-Based Lubrication System Based on Nanoparticular TiO2 with Superior Friction and Wear Properties

We evaluated the performance of five different commercially available nanoparticle classes as additives for an oil-based lubrication system. While the silicon dioxide particles Aerosil® 300, RY300, and R972V tended to increase wear and friction in our 100Cr6 versus cast iron disc–disc contact, Aeroxide® P 25 and especially T 805 TiO2 nanoparticles showed superior anti-wear and anti-friction properties. The underlying tribological mechanism was investigated with optical microscopy, helium ion microscopy, and X-ray photoelectron spectroscopy. Subsequently, we formulated a stable lubrication system based on the best performing T 805 particles. Here, the base oil is a highly purified paraffin oil which was supplemented with 1 wt% T 805 TiO2 particles, 1 wt% Estisol® 242 or 1 wt% oleic acid, 0.15 wt% oleylamine, and 0.15 wt% Pluronic® RPE 2520. Superior lubrication and anti-wear properties of this formulation were demonstrated in 4-h test runs with a normal force of F N = 2.5 kN and a sliding velocity of 0.15 m/s in our disc–disc contact. Wear was significantly reduced along with a nearly 12-fold reduction in the friction coefficient, compared to the base oil $$(\mu_{\text{base}}^{\text{fto}} = 0.155\;\;{\text{vs}} .\;\;\mu_{\text{T805}}^{\text{fto}} \approx 0.01)$$ . Using 100Cr6 disc–ball contacts, we additionally analyzed the properties of our lubrication system in the border friction regime under higher loads (F N = 0.5 kN) in 2-h runs. In particular, on the discs with lower engagement ratio, chemo-tribological protective layers were built, which protected the parts very well against wear.

The Influence of Barium Carbonate on the Tribological Characteristics of some Iron-Based Friction Composites

New iron-based composite materials with addition of barium carbonate (2 to 8 wt% barium carbonate) for friction applications are investigated. The tribological behavior of the studied materials was determined by a pin-on-disk method when a cast iron disk was employed. The addition of 2 wt% barium carbonate determined a significant increase of the average friction coefficient. Instead a further increase of barium carbonate content determined a gradual decrease of this parameter. The improvement of wear resistance was marked out for a barium carbonate content of up to 6 wt%. The optimal ratio between the average friction coefficient and the wear rate for the researched Fe-Cu-graphite-Ni-BaCO3 composites was determined for the iron-based material containing 2 wt% barium carbonate. SEM, EDX and XRD analysis marked out a complex structure containing alloyed ferrite, pearlite and carbides, traces of nickel and barium carbonate and free graphite.