Talib Ria Jaafar

Selection of Best Formulation for Semi-Metallic Brake Friction Materials Development

Brake friction materials play an important role in braking system. They convert the kinetic energy of a moving car to thermal energy by friction during braking process. The ideal brake friction material should have constant coefficient of friction under various operating conditions such as applied loads, temperature, speeds, mode of braking and in dry or wet conditions so as to maintain the braking characteristics of a vehicle. Besides, it should also posses various desirable properties such as resistance to heat, water and oil, has low wear rate and high thermal stability, exhibits low noise, and does not damage the brake disc. However, it is practically impossible to have all these desired properties. Therefore, some requirements have to be compromised in order to achieve some other requirements. In general, each formulation of friction material has its own unique frictional behaviours and wear-resistance characteristics.

Physical and Mechanical Properties of WC-Co Submicron Powders Using P/M Technique

The properties of WC-Co are greatly improved with the use of submicron powders. However, grain growth tends to occur during the sintering process which causes the properties to deteriorate to some extent. Free carbon and vanadium carbide are added in this study to serve as grain growth inhibitor. The effect of these two materials is evaluated based on WC-Co properties. In this work, the powders are mixed together via wet mixing process, compacted and undergo cold-isostatic pressing (CIP) before the samples are sintered in the temperature range of 1350-1450°C under nitrogen-based atmosphere. The physical and mechanical properties of the WC-Co sintered powders were analysed. Based on the work done, the WC-Co-C has a better properties compared to WC-Co-VC.

Influence of steel fibres on friction behaviours with respect to speed, pressure and temperature

Purpose This study aims to investigate the effect of different volume percentage (Vol.%) of steel fibre on the pressure, surface temperature and speed sensitivity behaviour during braking process as known brake effectiveness and to propose the best steel fibre Vol.% in the formulation. Design/methodology/approach Three brake pads composed of three different steel fibre volume percentages were fabricated through powder metallurgy route. Selecting one sample as based formulations, steel fibre (Vol.%) was decreased and increased by 50 per cent in the other two samples, respectively. The other ingredients are proportionally increased and decreased accordingly to the base formulation. The samples were tested for determining their hardness, porosity and coefficient of friction (COF) using Rockwell hardness tester, hot bath and brake inertia dynamometer, respectively. Findings Test results indicated that Sample T1 which composed of 9 Vol.% of steel fibre had the lowest COF and was sensitive to applied pressure, surface temperature and speed. The samples which composed of 18 and 27 Vol.% of steel fibre were having the same trend of COF and were sensitive to surface temperature and speed. Sample T which composed of 18 Vol.% of steel fibre had lower brake pad and disc lost as compared to Sample T2 which composed of 27 Vol.%. Mechanical properties did not show any significant correlation with COF sensitivity with temperature, speed and pressure. Originality/value The sample with 18 Vol.% of steel fibre was found to be the best formulation which produced acceptable COF; less sensitive to temperature, pressure and speed during braking process; and better wear resistance of brake pad as well as the rotor.

Physical and mechanical properties of injection moulded 316L stainless steel using waste rubber binder

Metal Injection Moulding (MIM) is a cost-effective method in producing a variety of small and high performance parts. This paper investigates the influence of waste rubber binder combined with polyethylene binder on the properties of injection moulded 316L stainless steel. Feedstock formulation was prepared using 32 µm 316L SS powder and mixed with binder system containing 55 wt.% paraffin wax, 35 wt.% PE/WR and 10 wt.% stearic acid. The feedstock was then successfully injection moulded at powder loading of 0.65. The specimens were immersed in n-heptane for five hours at 60 °C in order to remove the paraffin wax and stearic acid. Debinding process produced the defect-free green parts. The parts were then sintered in vacuum atmosphere at temperature ranges of 1320 °C to 1360 °C. The results showed that the highest density achieved was 7.612 g/cm3 at temperature of 1360 °C with tensile strength of 497 MPa while the highest hardness was achieved at 274.8 HV.

Optimization of Warm Compaction Process Parameters in Synthesizing Carbon-Copper Composite Using Taguchi Method

Carbon–copper composites are attractive materials used for electrical applications, such as brushes for engines and generators, slip rings, switches, relays, lugs, contactor and current collector. Various methods can be used to prepare Carbon-copper composite, such as infiltration, sintering, cold pressing, hot pressing or isostatic pressing. However, powder metallurgy route is seen to be most favorable due to its possibility of producing uniform microstructure and excellent net shape product. In this work, carbon-copper composite is prepared using powder metallurgy route with warm compaction process. The compaction pressure (A), compaction temperature (B), post baking temperature (C) and compaction time (D) were optimized by Taguchi method. Hardness and transverse rupture strength (TRS) were used to assess the effect of warm compaction process. The experimental design is according to the L9 (34) orthogonal array. Signal to noise and analysis of variance (ANOVA) are employed to analyze the effect of warm compaction parameters. It is found that the best parameters and their levels are A3B2C3D2 for the main effect of hardness and the best parameters and their levels for TRS is A3B2C3D1. It is also notified that optimized parameters of A3, B2 and C3 are identical for hardness and TRS. However, for parameter D, the best level for hardness is D2 and for TRS is D1. The ANOVA analysis proved that compaction temperature parameter is significant to hardness and TRS value whereas the others parameters are not significant.

Microstructure and mechanical properties of high speed steel with addition of ferrophosphorus on sintering temperature

High speed steel (HSS) is one of the important engineering materials especially for cutting material due to its superior properties. In this work, M2 HSS with addition of ferrophosphorus (Fe3P) are processed using conventional powder metallurgy route; mixing, compaction and sintering. The main objective of this work is to investigate the microstructure and mechanical properties ie, hardness and transverse rupture strength (TRS) in addition of Fe3P on sintering temperature. The mixtures are compacted at 15 tonnes and sintered at sintering temperature of 1100°C, 1140°C, 1180°C and 1220°C. The microstructural analysis using scanning electron microscope (SEM) shows the level of porosity decreases as sintering temperature increases which has indicated that denser sintered samples are obtained at high sintering temperature. The hardness result is in the similar trend where the hardness increases as sintering temperature increases. The maximum hardness of 458 HV is obtained at sintering temperature of 1220°C. Al...

Evaluation of Outlier Specific Correction Procedure for Areal Surface Texture

Surface texture data measured by optical type profilometer such as confocal microscope often contains outliers which may disturb the characterization of the surface texture. This paper evaluates an outlier specific correction procedure (OSCP) for areal surface texture data which can removes the outliers without affecting normal data points. The outliers are identified based on the median of its relative height to neighbouring data points within the detection window. The application of OSCP to areal topography data measured by confocal laser scanning microscope is compared to Gaussian filter and median filter. The result shows that, OSPC is better in outlier correction without affecting normal data points but there is a room of improvement.

Friction and Wear Characteristics of Cu-Based P/M Brake Friction Materials with Addition of Fe and C

Cu-based powder metallurgy friction materials were prepared by varying of Fe and C (% weight) in the friction components. The samples were compacted under the load of 24 metric tonnes and sintered at a temperature of 950 °C for 45 minutes. The friction and wear characteristics the materials developed were studied using Chase machine. The results show that Fe and C have different friction and wear characteristics. The friction coefficient of Cu-30%Fe-15%C sample maintained to be high and slightly increased after the drum temperature of 350°C and subsequently stable throughout tests. The friction of Cu-20%Fe-10%C stable until the drum temperature of 450°C and then its start to decay slightly until the end of the test. On the hand, the friction of Cu-10%Fe-5%C start to decay after sliding a few minutes at the drum temperature of 230°C. Thus, it could be postulated that the friction coefficient increased with increasing weight percentage of Fe and C in the friction components. However, the volume loss shows that there is no direct correlation with the Fe and C content. The volume loss of Cu-10%Fe-5%C was higher than the two samples which had the lowest hardness. On the hand, the volume loss of the Cu-30%Fe-15%C was slightly higher than Cu20%Fe-10%C as result of higher porosity and lower hardness. Wear mechanisms of abrasion, adhesion and thermal were observed to be operated during sliding process.

Effect of Heat Treatment Process of Sintered M3/2 High Speed Steel Parts

Dry machining is one of the ways to achieve a reduction of cooling lubricants, as well as reduced environmental pollution and lower health risk to workers. This leads to higher mechanical and thermal loading on cutting edges. The adaptation of cutting tools to the requirements of dry machining includes the optimisation of manufacturing technologies, the development of cutting materials of sufficient toughness and high hot hardness, the design of tool geometries as well as the coating of tools [.