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Changes with temperature in the microstructure and oxide formation of AlSiTiN, CrAlTiN, and CrAlSiTiN coatings were systematically studied using various characterisation techniques. By correlating these results with their tribological behaviour seen in the reciprocating sliding tests, it was concluded that SiO2 was more lubricous than Cr2O3, and provided better wear protection. Although an increase in the amount of SiO2 produced in the tribo-layer resulted in a greater lubricating effect, Cr2O3 produced a much lesser of such benefit. The effect of SiO2 as lubricant was also seen in machining. In the machining of stainless steel at 100 m/min, where flank and notch wear was due to abrasion and mechanical cracking, the CrAlSiTiN coated tools with the highest hardness, H/E, and H3 /E2 exhibited the highest wear resistance. However, AlSiTiN coated tools demonstrated reduced flank wear and the lowest wear in machining at 200 m/min. The formation of SiO2 could account for this low level of wear.

Changes with temperature in the microstructure and oxide formation of AlSiTiN, CrAlTiN, and CrAlSiTiN coatings were systematically studied using various characterisation techniques. By correlating these results with their tribological behaviour seen in the reciprocating sliding tests, it was concluded that SiO2 was more lubricous than Cr2O3, and provided better wear protection. Although an increase in the amount of SiO2 produced in the tribo-layer resulted in a greater lubricating effect, Cr2O3 produced a much lesser of such benefit. The effect of SiO2 as lubricant was also seen in machining. In the machining of stainless steel at 100 m/min, where flank and notch wear was due to abrasion and mechanical cracking, the CrAlSiTiN coated tools with the highest hardness, H/E, and H3 /E2 exhibited the highest wear resistance. However, AlSiTiN coated tools demonstrated reduced flank wear and the lowest wear in machining at 200 m/min. The formation of SiO2 could account for this low level of wear.

This work illustrated the preparation of highly dispersive carbonized sawdust by surface functionalization through a facile mild hydrothermal treatment with an aqueous mixture of reactants, potassium persulfate and potassium hydroxide (KPS:KOH), at 160 °C. The dispersion, morphological and purity analyses play an important role in the determination of the optimal hydrothermal process parameters. Dispersion test unveiled well dispersed modified carbonized sawdust's in polar solvent (ethanol) and no significant morphological changes according to the field emission scanning electron microscopy (FESEM) images. The intensity ratio (ID/IG) from the Raman measurement displayed an increased in the modified carbonized sawdust's ID/IG which indicated successful surface functionalization. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra revealed the introduction of various functional groups onto the carbonized sawdust surface, while the increment in the oxygen and potassium elements percentage (at. %) based on the energy dispersive X-ray system (EDX) supported both FTIR and XPS findings. Carbonized sawdust treated in 1:3 M ratio of KPS:KOH mixture (0.07 M:0.21 M) for 60 min showed the best dispersion in ethanol for at least a month with high degree of functionalization and various oxygen based functional groups were attached on its surface.

This paper reviews the phase structures and oxidation kinetics of complex Ti-Al alloys at oxidation temperatures in the range of 600–1000 °C. The mass gain and parabolic rate constants of the alloys under isothermal exposure at 100 h (or equivalent to cyclic exposure for 300 cycles) is compared. Of the alloying elements investigated, Si appeared to be the most effective in improving the oxidation resistance of Ti-Al alloys at high temperatures. The effect of alloying elements on the mechanical properties of Ti-Al alloys is also discussed. Significant improvement of the mechanical properties of Ti-Al alloys by element additions has been observed through the formation of new phases, grain refinement, and solid solution strengthening.

High temperature thermal-mechanical stability of tribological thin coatings is extremely important to a large number of applications in modern industries. DC magnetron sputtering of single metallic element (Cr, Si) and alloy (Ni:Cr) targets formed transition metal nitrides film coatings, CrSiN and CrNiN onto M2 steel. High temperature in-situ synchrotron X-ray diffraction, in the range 25 ℃-700 ℃, obtained experimental data for a range of structural and mechanical properties. Furthermore, experimental room temperature Nanoindentation measurements, made before and after the in-situ heating cycle, provided corresponding hardness and shear modulus results. The structural results identified microstructure and phase transformation changes, while the mechanical results identified microstrain, hardness, elastic modulus and deformation resistance properties of the coatings. Density functional theory (DFT) and quasi-harmonic approximation (QHA) modelled the high temperature thermal and mechanical properties such as: Young's modulus, shear modulus and thermal expansion coefficients (populated up to 1200 ℃). Estimates of hardness are made by correlating the bulk phase hardness and shear modulus, of the CrN and Ni phases, as a function of temperature. Results indicate that Si doping enhances the hardness of the CrN framework, increasing from 29 to 36 GPa and improves the coatings elastic modulus, and resistance to deformation. However, the addition of Ni reduced these properties. Furthermore, formation of (Cr,Si)N and Ni(Cr) solid solutions is inferred from DFT, Rietveld and lattice constant analysis.

The present study investigated the preparation of solid carbon through the electrolysis of a newly formulated molten salt electrolyte containing CaCO3-Li2CO3-LiCl with a continuous cell voltage of 4 - 6V, and temperatures of 550 and 650°C. The process was carried out in a two-electrode cell using AISI 304 stainless steel electrodes in CO2 gas environment. CO2 gas was captured and electro-converted to solid carbon, and deposited on the cathode surface. SEM images revealed five dominant microstructures: grape-like, tubes, thread-like, spheres, and flakes. These materials consist of 69 - 80% carbon content based on EA analysis. Single wall nanotube structures of 13 - 90nm outer diameter was also detected under TEM analysis. The result revealed that electrolysis voltage and temperature changes affected the microstructures, quantity of the deposited carbon, and the efficiency of electro-conversion process. The size of the carbon microstructures declined, and carbon deposition rate increased as both voltage and temperature were increased. However, it reduced the efficiency of the process, thus using more energy per g of carbon produced.

Concrete strength monitoring, providing information related to the readiness of the structure for service, is important for the safety and resource planning in the construction industry. In this paper, a semi-analytical model of surface bonded piezoelectric (lead zirconate titanate) based wave propagation (WP) technique was developed for strength evaluation of mortar with different mix, throughout the curing process. Mechanical parameters of the mortar specimen were mathematically evaluated from the surface wave (R-wave) and pressure wave (P-wave) using elastic wave equations. These parameters were then empirically correlated to the strength. The model was found to be very robust as it could be generalized to account for different water to cement (W/C) ratio. The performance of the WP technique was then compared to the electromechanical impedance technique and other conventional techniques, such as the ultrasonic pulse velocity (UPV) test and the rebound hammer test. Results showed that the WP technique performed equally well as the conventional counterparts. The proposed technique is also advantageous over embedded WP technique and the UPV test, in terms of its capability to capture two types of waves for the evaluation of dynamic modulus of elasticity and Poisson’s ratio. A separate study was finally conducted to verify the applicability of this technique on heterogeneous concrete specimen. With the inherent capability of the WP technique in enabling autonomous, real-time, online and remote monitoring, it could potentially replace its conventional counterparts, in providing a more effective technique for the monitoring of concrete strength.

The effect of water and alkali treatment on the thermal decomposition of oil palm shell (OPS) together with the mechanical performance of polyester composites reinforced with treated OPS has been presented in this work. Treatment of OPS with cold/hot distilled water and cold alkali treatment were found to improve the tensile and flexural strength of the resulting composites although the highest mechanical performance was noted with the use of sonication in hot distilled water. On the other hand, hot alkali treatment was found to produce a composite mechanical performance similar to that of the hot distilled water treatment with sonication. FTIR tests indicated that adsorbed water molecules together with some parts of the hemicellulose and lignin were removed by the treatments. Thermogravimetric analysis and scanning electron microscopy of the treated OPS with hot alkali (1–9% concentration) showed that the mechanical performance reach a peak at 7% alkali concentration with a further increase in concentration resulting in a significant lignin mass loss and decrease in mass residue of the OPS. This trend was attributed to the higher alkali concentration removing hemicellulose as a binder for the cellulose and lignin which resulted in debonding between the filler and matrix components of the OPS and hence a deterioration in fiber structure and resulting poor composite mechanical performance. Therefore, it was concluded that the optimum concentration of alkali treatment required for maximum mechanical performance of natural filler reinforced polymer composites can be obtained simply from thermogravimetric analysis. POLYM. COMPOS., 2016. © 2016 Society of Plastics Engineers

The surface of the mild steel carburized using Na2CO3-NaCl was dominated by retained austenite. Towards the core, the amount of austenite reduced while the amount of martensite increased. Increasing the duration of the carburization resulted in higher peak hardness and case depth. It also increased the amount of cementite in the grain boundaries and the austenite grains size, rendering the steel more susceptible to cracking. The superior wear resistance of the martensite, as compared to the austenite, could be attributed to its high cracking and adhesive wear resistance owing to its high hardness and tendency to form oxides. The friction was governed by the wear mechanism and the type of microstructure at the worn scar sliding on the carbide ball.

Surface wave propagation (SWP) technique employing Lead Zirconate Titanate (PZT) transducer has recently been found to be a useful tool in concrete hydration monitoring. In this paper, the performance of PZT based SWP technique was compared with the conventional techniques such as ultrasonic pulse velocity (UPV) test, rebound hammer (RH) test and concrete compression test. Results showed that the SWP technique, in addition to its inherent advantages, performed equally well as the conventional counterparts in concrete strength prediction

Previous work shows that when a cantilever piezoelectric energy harvester with a given width is split into several pieces and then electrically connected in parallel, the output power increases substantially compared with when it acts in a single piece with a similar total width. It was hypothesized that this increase is due to the reduction in the damping of the width-reduced beam. As a result, the beam with the smaller width vibrates with higher amplitudes and therefore has higher energy harvesting capability. In this paper, this hypothesis is examined by measuring the damping of the cantilever beam as its width is reduced. It is shown that as the width decreases, the damping is reduced, which contributes to the increase in the harvested power. It is then shown that the harvested energy from an array of cantilever piezobeams with a certain total width is higher than that from a single-piece harvester of similar width. © 2015 IOP Publishing Ltd.

This paper examines the effectiveness of palm oil methyl ester (POME) as lubricant additive using the four-ball and milling tests. In milling 55 HRC-stavax® (modified AISI 420 stainless steel) under flood lubrication, three stages of tool wear occurred: 1) initial wear by delamination, attrition and abrasion; 2) cracking at the substrate, 3) followed by formation of individual surface fracture at the cracks which would then enlarge and coalesce to form a large fracture surface. Mineral oil sprayed in mist form was more effective in reducing the coating delamination and delaying the occurrence of cracking and fracture. The effectiveness of mineral oil in suppressing these wear modes could be enhanced by the presence of POME. The mechanism by which the POME suppressed these wear modes could be explained by the results obtained in the four-ball tests which showed that the presence of POME as additive in the mineral oil reduced the friction coefficient, severity of welding and increased the critical load for welding to occur.

One of the famous heritages in Sabah is the traditional musical instrument called sompoton. This instrument has several parts with the vibrator being the most important of all. In this paper, the vibrator is modeled as a cantilever beam with uniformly distributed mass. Using this model, the fundamental frequency is analyzed using Rayleigh’s energy theory. The vibrator made from aluminum is fabricated at different dimensions and is excited using constant air jet to obtain its fundamental resonance frequency. The measured fundamental frequency is then compared with the theoretical values calculated based on cantilever beam model and Rayleigh’s energy theories. It was found that the experimental and theoretical results exhibit the same trend but differ in magnitude. To overcome this, a correction factor is added to the theoretical formulation to account for fabrication error.

Spare parts inventory management is very important to ensure smooth operation of maintenance department. The main objectives of inventory management of spare parts are to ensure the availability of spares and materials for the maintenance tasks and increase the productivity of the maintenance department. This research centred on the development of the Computerised Inventory Management System (CIMS) for the maintenance team at Weida Integrated Industries Sdn. Bhd. The inventory management technique used to control the spare parts inventory in this research was the basic Economic Order Quantity models (EOQ). However, the CIMS developed is unique as it has the ability in handling inventories in multiple-storage locations. The CIMS was written using the Visual Basic 2010 software. This CIMS has the abilities to keep records and process the spare parts information effectively and faster besides helping the user to perform spare parts ordering tasks compared to the current manual recording. In addition, the ordering quantity and frequency for the CIMS is determined through the EOQ technique. However, observation indicates that the overall average inventory level currently at the factory is lower than the expected overall average inventory level produced by the CIMS. This is due to the fact that the CIMS was unable to consider the opening stock in ordering the inventories. Therefore, further improvements are needed to optimize the performance of the system such as using the EOQ with the reorder point technique, the periodic or continuous review system.

In order to prevent possible damages to the spindle systems, reliable monitoring techniques are required to provide valuable information on the condition of the spindle condition. A technique is proposed for monitoring spindle bearings conditions via the use of acoustic emission (AE) signals, which implements Hilbert–Huang transform (HHT) analysis to extract the crucial characteristic from the measured data to correlate spindle running condition. The HHT becomes a promising technique in extracting the properties of nonlinear and non-stationary signal. However, the original HHT has several deficiencies, which eventually lead to misinterpretation to the final results. The improved version of HHT is proposed and used to overcome the weakness of the original HHT. The simulation and experimental results are used to verify the effectiveness of the WPD–HHT and therefore Hilbert marginal spectral, compared to traditional Fourier transform. Experimental results are presented to examine and explore the effectiveness of AE for monitoring spindle bearings conditions. It is concluded that good correlation existed between the results obtained by AE data and the increase in the preload, and change in the dimensions and geometry of the spindle bearings and their housings as the temperature increases. In support of this finding, vibration and acceleration data are also used to assess the amount changes in the antistrophic stiffness and radial error motion.

In order to prevent possible damages to the spindle systems, reliable monitoring techniques are required to provide valuable information on the condition of the spindle condition. A technique is proposed for monitoring spindle bearings conditions via the use of acoustic emission (AE) signals, which implements HilbertHuang transform (HHT) analysis to extract the crucial characteristic from the measured data to correlate spindle running condition. The HHT becomes a promising technique in extracting the properties of nonlinear and non-stationary signal. However, the original HHT has several deficiencies, which eventually lead to misinterpretation to the final results. The improved version of HHT is proposed and used to overcome the weakness of the original HHT. The simulation and experimental results are used to verify the effectiveness of the WPDHHT and therefore Hilbert marginal spectral, compared to traditional Fourier transform. Experimental results are presented to examine and explore the effectiveness of AE for monitoring spindle bearings conditions. It is concluded that good correlation existed between the results obtained by AE data and the increase in the preload, and change in the dimensions and geometry of the spindle bearings and their housings as the temperature increases. In support of this finding, vibration and acceleration data are also used to assess the amount changes in the antistrophic stiffness and radial error motion.

Palm oil industry contributes significantly to Malaysian economy. However, there seem to be very few studies conducted on improving the palm oil production process. Specifically, there is seemed to be lacked of studies on the application of simulation modelling in improvement activities conducted on palm oil mills. This study addressed this gap by demonstrating the application of simulation modelling in improving or evaluating potential improvements before the improvements are being carried out in the palm oil mill. In order to conduct this research, a palm kernel plant production process in a local palm oil mill had been studied. Two models representing the existing and improved process had been developed and compared. The comparison indicated that the new improved model of the kernel plant does increase the system throughput by 26.7%.

This work examines the frictional and wear behaviour of AlCrN, TiN, TiAlN single­layer coatings, and TiAlN/AlCrN, AlN/TiN nano-multilayer coatings in dry sliding. Comparative studies on the coatings sliding in air and vacuum environment at different speeds provided important insight on the effect of oxidation and temperature on the frictional and wear behaviour of the coatings. Among all the single-layer coatings tested in vacuum, TiN gave the lowest coefficient of friction (COF), followed by TiAlN and AlCrN This indicated that TiN was the most lubricous coating. At 10 m/min in ambient air in which oxidation took place, AlCrN gave the lowest COF, followed by TiN and TiAlN Among the two types of nano-multilayer coatings tested in vacuum and air, the AlCrN/TiAlN produced lower COF. The characteristics of the COF produced by AlCrN/TiAlN and AlN/TiN in vacuum and air was similar to those produced Qy TiAlN and TiN, respectively. This showed that the COF of these nano-multilayer coatings was governed by TiAlN and TiN AlCrN exhibited the highest wear resistance. TiAlN had the lowest wear resistance. TiN, TiAlN/AlCrN and AlN/TiN which exhibited similar wear resistance, had lower wear resistance than AlCrN but higher wear resistance than TiAlN In air, increasing the speed from 10 m/min to 100 m/min resulted in a 'reduction in COF for all coatings, except AlCrN

This paper examines the friction behaviour of AlCrN and TiN PVD coatings in atmospheric air and vacuum using a ball-on-disc and a reciprocating tribotesters. Comparative study on the coating sliding in air and in high vacuum environment provides important insight on the effect of oxidation on the friction behaviour of the coatings. Other important factors such as load, sliding velocity, temperature effects on the frictional behaviour of these coatings were also investigated. In the ball-on-disc tests carried out in vacuum, (i) TiN gave lower coefficient of friction (COF) than AlCrN, indicating that TiN was more lubricous, (ii) higher speed resulted in lower COF, and (iii) the COF of both coatings were lower than that produced in air. In ambient air, (i) AlCrN gave lower COF than TiN with high wear debris retention on the sliding interface due to the effect of oxidation, and (ii) higher speed resulted in lower COF, similar to that observed in vacuum. In the reciprocating tests, at low load, increasing the temperature from room temperature to 150 °C resulted in a reduction in the COF. However, at high load, the temperature virtually did not affect the COF. Higher nominal load resulted in lower COF while higher speed resulted in higher COF.

This paper examines the effectiveness of POME (palm-oil methyl ester) as lubricant additive based on the results obtained in the four-ball and milling tests. The results produced in the four-ball tests showed that small amount of POME as an additive in the mineral oil resulted in shorter running-in period, lower steady-state friction coefficient and degree of adhesion, and higher weld load. The presence of POME enhanced the effectiveness of the mineral oil in suppressing coating delamination and delaying the occurrence of cracking and fracture on the flank face of the tool during milling of stavax ® (modified 420 stainless steel). The results obtained in the four-ball tests suggested that this was due to a reduction in the cutting forces and lesser degree of welding of asperities brought about by the presence of POME.

Nowadays the energy source for portable electronic devices heavily depends on battery which has limited lifetime and contributes to environmental pollution after discarding it. This has created an environment impact to the soil and water. A green solution to reduce excessive pollution from battery usage is suggested in this paper with the use of piezoelectric materials to convert ambient vibration into the required electrical energy. The piezoelectric material is adhered to a cantilever beam to form a piezoelectric bender and its analytical model with base excitation is first established to study the effect of the structural and connecting configurations of the constructed benders on the harvested electric charge. The model predicts that the single-active layer piezoelectric bender harvests about 1.6 times of electric charge and two-active layer piezoelectric bender in parallel connection harvests two times, than that harvested by two-active layer piezoelectric benders in series connection. The experimental results comply with the theoretical predications. Among all the combinations, the two-active layer piezoelectric bender in parallel connection is concluded the optimum configuration for electrical charges harvesting. It is also shown in this paper the application of piezoelectric charge harvester to light up LED. This shows the potential application of piezoelectric charge harvester to replace battery usage that may reduce heavy mental pollution to the environment.

This paper reports on the fracture behavior of a hard wood known as Selanga Batu (Shorea spp) with different structure under tensile stress at various strain rates (10-100mm/min). It was found that the structure had significant effect on the modulus of elasticity and yield strength of the wood. Wood with high percentage of ray parenchyma exhibited lower modulus of elasticity and yield strength. Ray parenchyma in wood acted as the weakest plane for crack to propagate in a step-wise manner. However, large variation found in test results make it not possible to evaluate whether the strain rate affects the ultimate strength and the fracture strain. Since the values of the modulus of elasticity obtained at a given strain rate had very small variation, the effect of strain rate on the modulus of elasticity and yield strength could be examined. It was found that the strain rate did not affect the modulus of elasticity and the yield strength of the wood.

This paper evaluates the performance of TiAlN/AlCrN nano-multilayer coated, TiAlN single-layer coated and uncoated carbide tools in low-speed milling of STAVAX (modified 420 stainless steel) under flood and mist lubrication. Scanning electron microscope, energy dispersive X-ray analysis system and Raman spectroscopy were used to examine the tool wear and determine the type of oxide formed on the tool surface during machining. In machining STAVAX with a hardness of 40 HRC, the coated tools were subjected to delamination, attrition and abrasive wear throughout the duration of testing. During machining STAVAX with a hardness of 55 HRC, three distinct stages of tool wear occurred, (i) initial wear by delamination, attrition and abrasion, followed by (ii) cracking at the substrate and (iii) the formation of individual surface fracture at the cracks which would then enlarge and coalesce to form a large fracture surface. The TiAlN/AlCrN coated tool exhibited higher resistance against delamination and abrasive wear than the TiAlN coated tool. The cracking resistance and hardness of the coating, and oxidation of the coating during machining appeared to have significant influences on the resistance of the tool against these wear mechanisms. A longer cutting distance was required to cause TiAlN/AlCrN coated tool to crack and fracture. This was due to the substrate receiving greater protection against cracking and fracture as a result of the coating being removed at a slower pace by abrasion and delamination. The likeliness of the uncoated tool to chip, crack and fracture, and the severity of abrasion increased with an increase in the hardness of the workpiece. Small quantity of mineral oil sprayed in mist form was effective in reducing the severity of delamination and abrasive wear, and delaying the occurrence of cracking, fracture and chipping. The influence of the ductility of the workpiece, tool wear and the lubricants on the surface finish are also discussed. © 2010 Elsev

The performance of coated carbide tools and the effectiveness of mist and flood lubricants in low-speed milling of STAVAX were studied. The flank wear increased with an increase in the hardness of the workpiece. The mist lubricant (a solution containing 93 vol% liquid paraffin oil and 7 vol% cyclomethicone sprayed in mist form) was more effective than the flood lubricant (an emulsified water-based coolant with 9% concentration of Shell Dormous BL oil) in reducing flank wear. Under flood lubrication condition, the cutting distance required to cause TiAlN coated tool to fracture was longer than that required for the TiAlN/AlCrN coated tool. The mist lubricant was effective in delaying the occurrence of cracking on the TiAlN coated tool. Under mist lubrication condition, no cracking and fracture occurred on the TiAlN/AlCrN coated tool throughout the duration of testing. This is an abstract of a paper presented at the World Tribology Congress (Kyoto, Japan 9/6-11/209).

Ultra-precision machines are widely used to turn aspherical or spherical profiles on mold inserts for the injection molding of optical lenses. During turning of a profile on a stainless steel mold insert, the cutting speed reduces significantly to 0 as the cutting tool is fed towards the center of the machined profile. This article reports on experiments carried out to study the wear of uncoated, physical vapor deposition (PVD) coated and chemical vapor deposition (CVD) coated carbide tools in the ultra-precision machining of STAVAX (modified AISI 420 stainless steel) at low speeds with and without a lubricant. A sprayed mixture of compressed air, liquid paraffin oil, and cyclomethicone was used as a lubricant. During machining at 44 m/min under dry condition, the rake face of the tool edge was predominantly subjected to abrasive wear. Reducing the speed to 10 m/min increased the flank wear and the severity of abrasive wear and caused the tool edge to fracture, leading to a deterioration of the surface finish. The lubricant was effective in preventing surface fracture, reducing flank wear, and improving the surface finish. Among the PVD-coated and the CVD-coated tools, the former tool type is more suitable to be used in ultra-precision machining. The CVD-coated tool vibrated rapidly, causing extensive fracture to take place on the flank face and the surface finish to be undulating. The experimental results obtained in the turning tests gave useful insight on the appropriate parameters and conditions to be used in the machining of a profile on a mold insert. The profile machined on the stainless steel mold insert with the PVD-coated carbide tool in the presence of natural oil had a superior form of accuracy and surface finish.

Purpose: This paper discusses the experimental work carried out to investigate the performance of coated carbidetool in ultra-precision machining of stainless steel and evaluates whether this tool can be used to fabricate a cavitywith high form accuracy and surface finish on a stainless steel mould insert. Design/methodology/approach: The results obtained in the turning process and the machining of cavity ona mould insert under various conditions and parameters are examined. Findings: The experimental results obtained in the turning tests gave an important insight of the appropriateparameters and the condition to be used in the machining of cavity on a mould insert. The cavity machined on thestainless steel mould insert with the coated carbide tool in the presence of natural oil has superior form accuracyand surface finish. Research limitations/implications: Further research is needed to investigate the performance of the coatedcarbide tools in machining profiles of other shape and diameter. Practical implications: Profile with a superior form accuracy and surface finish can be machined on a stainlesssteel mould insert using a coated carbide tool instead of using a PCBN tool, a much more expensive tool. Originality/value: The paper presents original information on the ultra-precision machining of tool steels at lowspeeds. The paper is of interest to manufacturing engineers.

A study was undertaken to investigate the wear of PVD-coated carbide and uncoated carbide tools during milling of STAVAX (modified AISI 420 stainless steel) at low speeds. No significant change in the tool wear was observed when the cutting speed was increased from 25 to 50 m/min. It was found that increasing the hardness of the workpiece from 35 to 55 HRC caused a marked increase in the flank wear and a change in the dominant wear mechanism. In machining STAVAX with a hardness of 35 and 40 HRC, the coated tool was predominantly subjected to abrasive wear throughout the duration of testing. During machining STAVAX with a hardness of 55 HRC with the coated tool, three distinct stages of tool wear occurred, (i) initial wear by abrasion, followed by (ii) cracking and chipping, and (iii) the formation of individual surface fracture at the cracks which would then enlarge and coalesce to form a large fracture surface. The coated tool showed much higher fracture resistance than the uncoated tool. The high fracture resistance exhibited by the coated tool could be attributed to the effectiveness of the coating in preventing the formation of cracks which would act as preferential sites for fracture to take place. The experimental results also show that coating prevents edge chipping and enhances the abrasive wear resistance of the tool. Both the ductility of the workpiece and the tool wear appeared to have influences on the surface finish of the workpiece. It was found that the cutting fluid was effective in preventing catastrophic failure of the tool. © 2007 Elsevier B.V. All rights reserved.

Experiments were carried out to investigate the effect of humidity on the wear behaviour of same metal combination, i.e. steel-steel and aluminium-aluminium. The sliding wear of steel was found to increase by nearly 1.5 orders of magnitude when the relative humidity (RH) of the surrounding air decreased from 80 to 28% RH. At low humidity, both delamination and adhesion wear occurred. At high humidity levels, both delamination and adhesion wear took place at a relative small scale and the frictional force was considerably lower than that obtained at lower humidity levels. It is proposed that the low wear occurring at high humidity levels is due to the inhibition of these wear mechanisms by the formation of interfacial layers, possibly iron hydroxide and ferri-oxide-hydrates, and the adsorption of water on the worn surface in addition to the normal atmospheric oxidation. Increasing the humidity from 28 to 80% RH. increased the wear rate of aluminium by nearly half an order of magnitude. It is proposed that at higher humidity levels, water vapour adsorbs on both the freshly created surface and wear debris generated and therefore the wear debris egresses easily from the contact area without adhering to the parent surfaces. Lack of adhering wear debris exposed the worn surfaces to metal-metal interaction.

This paper reports on experiments carried out to study the performance of various type of polycrystalline cubic boron nitride (PCBN) and polycrystalline diamond (PCD) cutting tools during machining of aluminium alloy reinforced by silicon carbide metal matrix composite (Al-SiC MMC). While different wear modes were observed on the surfaces of the cutting tools, the surface finish was found to be governed by the notch wear formed on the flank face and the transfer of work material onto the workpiece. During machining, the PCBN tools were subjected to intergranular fracture, and the amount of work material adhering onto the tool and the workpiece increased significantly with cutting speed. While it was found that the use of coolant could result in a marked reduction in the amount of work material on the machined workpieces, it could also cause an increase in the severity of abrasion between the flank face and the machined surface. This in turn led to an increase in notch wear and thus a deterioration of the surface finish. These detrimental effects were more pronounced at low cutting speed using a fine-grained and binderless PCBN tool. PCD tools exhibited better performance than PCBN tools because they possessed higher abrasion and fracture resistance, and lower adhesion property with the work material.

Ultra-precision machines are widely used to turn aspherical profiles on mould inserts for the injection moulding of optical lenses. During turning of a profile on a stainless steel mould insert, the cutting speed reduces significantly to 0 as the cutting tool is fed towards the center of the machined profile. This paper reports on experiments carried out to study the wear of uncoated, PVD-coated and CVD-coated carbide tools in the ultra-precision machining of STAVAX (modified AISI 420 stainless steel) at low speeds.

Ultra-precision machines are widely used to turn aspherical or spherical profiles on mould inserts for the injection moulding of optical lenses. During the turning of a pro. le on a stainless steel mould insert, the cutting speed reduces significantly to 0 as the cutting tool is fed towards the centre of the machined pro. le. This paper reports experiments carried out to study the wear of uncoated and PVD-coated carbide tools ( carbide tool coated with 2000 alternate layers of AlN and TiN, each layer 1.5 nm and carbide tool coated with 0.5 mum TiN, 5.5 mum TiCN and 0.5 mum TiN) in the ultra-precision machining of STAVAX ( modified AISI 420 stainless steel) at low speeds with and without lubricant. A sprayed mixture of compressed air, liquid paraffin oil and cyclomethicone was used as lubricant. Examination of the wear at the rake face of the tool suggests that during machining of the alloy with a hardness of 55 HRC without lubricant, the cutting edge is subjected to high compressive stress, resulting in fracture. Reducing the hardness of the alloy would therefore result in a lower stress acting on the cutting edge, thus rendering the tool less susceptible to fracture. Both the rake and the flank faces of the coated tools exhibited lower wear than the uncoated tools. This was due to the former tools possessing higher fracture resistance owing to the presence of the coating. The lubricant was effective in improving surface finish, preventing surface fracture and reducing flank wear.