Papers by Keyword: Warm Compaction

Abstract: Pantograph slide materials demand excellent mechanical and electrical properties for rail applications. Carbon-copper (C-Cu) composites combine the high electrical conductivity of copper with lightweight and wear-resistant traits of carbon. Using palm kernel shells (PKS), a palm oil industry by-product, promotes sustainability but presents challenges in achieving uniform distribution and performance retention. This study examined PKS and graphite as carbon sources in C-Cu composites enhanced with carbon nanotubes (CNT), focusing on optimising mechanical and electrical properties for pantograph slides. However, CNT is known for its difficulty in achieving optimum dispersion in composites, as strong van der Waals forces cause aggregation, uneven distribution, and porosity, thereby reducing the electrical and mechanical properties. Balancing carbon content, CNT reinforcement, copper, and resin matrix is crucial to prevent conductivity loss and structural weaknesses. Varied CNT content (1wt% to 5wt%) was analysed for its impact on hardness, transverse rupture strength (TRS), and electrical resistivity of the C-Cu composite. Fabrication involved material mixing, cold pressing, warm compaction (150°C, 490 kN, 5 minutes), and post-baking process (250°C, 4 hours). The 2 wt% CNT sample achieved superior results, including 102.5 HRR hardness, 37.63 MPa TRS, and 32 µΩ.m resistivity before post-baking, due to excellent CNT dispersion. Post-baking enhanced bonding and mechanical properties but raised resistivity by altering conductive pathways. Poor dispersion of CNT at contents more than 3 wt% led to agglomeration and inferior properties. The findings highlight the critical role of CNT dispersion and the post-baking process in achieving optimal composite performance to maximise CNT potential. These results are comparable to commercial pantograph slides, contributing to the development of high-performance materials for rail applications.

Abstract: 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.

Abstract: The carbon-copper (C-Cu) composites combine the positive characteristics of thermal and electrical conductivity from Cu, low thermal expansion coefficient and lubricating properties from conventional graphite. For that particular application, C-Cu composites are widely used as electrical contact devices such as carbon brushes and current-collector for railway power collection system. Due to economic and environment concern, activated-carbon produced from MPOB’s oil palm kernel shell (OPKS) is studies as replacement for conventional graphite. The OPKS is crushed and mixed with copper and resin powder before it is compacted into shape. Then the green body undergoes warm-compaction (1140MPa;100-150°C) followed by post-baking (150-250°C) process to enhance its properties. The physical and mechanical properties of the C-Cu composite were analysed. The resulting microstructures, electrical and wear properties also are presented and discussed. The prototype of current-collector for PUTRA LRT and carbon brushes for electrical applications was produced from this research work.

Abstract: This paper presents the alloyability of FeCrCu powder compacts formed through warm powder compaction route. A lab-scale uni-axial die compaction rig was designed and fabricated which enabled the powder forming at elevated temperature. Iron powder ASC 100.29 was mechanically mixed with other alloying elements, i.e., copper (Cu) and chromium (Cr) as well as carbon (C) as additive for 60 minutes. Green samples were formed at 30°C (room temperature), 100°C, and 180°C through simultaneous upward and downward axial loadings. The defect-free green compacts were subsequently sintered in argon gas fired furnace at 900°C and 1000°C for 60 minutes at a rate of 5°C/minute. The alloyability of the sintered products was analyzed through XRD testing. The compressive strength of the sintered samples was also measured. The results revealed that FeCrCu alloy was formed at different intensity depended upon the forming and sintering temperature. The compressive strength was found to be highest for sample formed at 180°C and sintered at 1000°C.

Abstract: Increasing density is the best way to increase the performance of powder metallurgy materials. Conventional powder metallurgy processing can produce copper green compacts with density less than 8.3g/cm³ (a relative density of 93%). Warm compaction, which is a simple and economical forming process to prepare high density powder metallurgy parts or materials. CuSn matrix composites with %2 weight fractions of reinforcement particles were prepared using warm compaction and sintering. Micro-structural aspects were observed by optical microscope. Density, hardness and wear tests were also performed. Abrasion resistance measurements were used to study the abrasive behaviors of CuSn matrix and its composites. The effects of reinforcement and preparation methods on the microstructure and mechanical properties of composites have been investigated.

Abstract: By applying new warm compaction forming technology of wood power developed through material forming theories in some interdisciplines such as applied science of wood and powder metallurgy, cotton stalk powder (CSP) was used as base material to prepare CSP/Al composite material of which the modulus of rupture and internal bond strength could be up to 83.95MPa and 6.82MPa respectively, wear resistance was 0.05g/100r and water absorption 0.65%. The sliding bearings made of the composite materials had a crushing strength and an apparent hardness up to 91.22MPa and HB51.1 separately. They are expected to replace sintered bronze of powder metallurgy in producing sliding bearings for light textile machinery so as to reduce the usage of nonferrous metal. The application of CSP/Al composite material explores a new way to use wood residuum in agriculture and forestry and ensure its high quality and cleanness.

Abstract: Effects of Sintering atmosphere and temperature on properties of warm compacted 410L stainless steel powder were studied. Sintered density, hardness, tensile strength and elongation were measured. Results showed that in order to achieve high comprehensive properties, the optimal sintering temperature was 1230°C for 410L stainless steel powder. At the same sintering temperature, density and hardness sintered in vacuum were much higher than that sintered in cracked ammonia while tensile strength sintered in cracked ammonia were much higher than that in vacuum. When sintered in vacuum at 1230°C, sintered density was 7.45 g•cm-3, hardness was 65 HRB, tensile strength was 410 MPa and elongation was 29.5%. When sintered in cracked ammonia atmosphere at 1230°C, sintered density was 7.26 g•cm-3, hardness was 97 HRB, tensile strength was 515 MPa and elongation was 3.8%.

Abstract: Warm compacting behavior and sintering performance of 316L stainless steel powders were studied. Results showed that green density and strength of samples made in warm compaction were much higher than that in cold compaction. Under pressure of 700MPa, green density and strength in warm compaction were 7.01 g•cm^-3 and 30.7MPa, which were higher than cold compaction by 0.19 g•cm^-3 and 10.7MPa. When sintered in hydrogen-nitrogen atmosphere for 60 minutes, sintered density, tensile strength and elongation all increased with the rise of sintering temperature. At 1300°C, Sintered density, tensile strength and elongation were 7.42 g•cm^-3, 545MPa, 28.0%, respectively.

Abstract: Utilization of MSC.Marc FEM software, the typical warm compaction process of molybdeum powder was simulated. Influence of processing parameters of warm compaction on green density of molybdenum powder were studied. Furthermore, the commonly defect existing in green body were analyzed. The results show that compaction pressure is an important factor on green density. At the beginning of warm compaction, average relative density rises linearly along with the increasing pressure. The green density increases with the suppression speed increasing, when velocity value reaches 7mm/s the density will not increase anymore. After the value of friction coefficient is greater than 0.1,green density decreases with the friction coefficient increasing. Influence of temperature on compaction is improvement of the lubrication condition, and reduces the friction coefficient. The appearance of axial tensile stress is the important factor which causes delamination and cracks. Internal friction and lubrication condition of powder mixed system is the important reason results in defect.

Abstract: Fe-1.5Cu-1.5Ni-0.5Mo-0.3C alloy was prepared by powder metallurgy (P/M) warm compaction. Under the conditions of compaction pressures of 600 or 800 MPa and compaction temperature of 100 or 120°C , sintered in cracked ammonia atmosphere at 1120°C for half an hour, the researched alloy samples with higher properties could be prepared. The results show: when formed at a compaction pressure of 800 MPa and compaction temperature of 120°C , the alloy presented a sintered density 7.41g/cm³, hardness 88HRB, ultimate tensile strength 593MPa， yield strength 585MPa, and elongation 3.8%. Their mechanical properties, crack morphology and surface composition weres analyzed.