Search results

The purpose of this paper is to optimize the laser-assisted jet electrochemical machining parameters, namely, supply voltage, inter-electrode gap, duty cycle and electrolyte concentration during machining of WC-Co composite using grey relational analysis and fuzzy logic.

In this work, experiments were carried out as per the Taguchi methodology and an L16 orthogonal array was used to study the influence of various combinations of process parameters on material removal rate, hole taper angle and surface roughness height. As a dynamic approach, the multiple response optimization was carried out using grey relational analysis and fuzzy logic.

The process parameters were optimized using grey relational analysis and fuzzy logic for different machining conditions such as balanced manufacturing, high-speed manufacturing and high-quality manufacturing. The research documented in this paper can be scaled up for case studies regarding industrial applications to compare optimization methods for manufacturing processes that are already being carried out.

An attempt to optimize material removal rate, hole taper angle and surface roughness height together by a combined approach of grey relational analysis and fuzzy logic has not been previously done.

WC-Co is a well-known material for conventional tooling but is not yet commercially available for additive manufacturing. Processing it by selective laser sintering (SLS) will pave the way for its commercialization and adoption.

It is intended to optimize process parameters (laser power, hatch spacing, scan speed) by fabricating a bigger part (minimum size of 10 mm diameter and 5 mm height). Microstructural analysis, EDX and hardness testing is used to study effects of process parameters. Optimized parameter is ascertained after fabricating 49 samples in preliminary experiment, 27 samples in pre-final experiment and 9 samples in final experiment.

Higher laser power gives rise to cracks and depletion of cobalt while higher scan speed increases porosity. Higher hatch spacing is responsible for delamination and displacement of parts. Optimized parameters are 270 W laser power, 500 mm/s scan speed, 0.04 mm layer thickness, 0.04 mm hatch spacing (resulting in energy density of 216 J/mm3) and 200°C powder bed temperature. A part comprising of small hole of 2 mm diameter, thin cylindrical pin of 0.5 mm diameter and thin wall of 2 mm width bent up to 30° angle to the base plate is fabricated. In order to calculate laser energy density, a new equation is introduced which takes into account both beam diameter and hatch spacing unlike old equation does. In order to calculate laser energy density, a new equation is formulated which takes into account both beam diameter and hatch spacing unlike old equation does. WC was not completely melted as intended giving rise to partial melting-type binding mechanism. This justified the name SLS for process in place of SLM (Selective Laser Melting).

Using all possible combination of parameters plus heating the part bed to maximum shows limitation of state-of-the-art commercial powder bed fusion machine for shaping hardmetal consisting of high amount of WC (83 wt. per cent).

The research shows that microfeatures could be fabricated using WC-Co which will herald renewed interest in investigating hardmetals using SLS for manufacturing complex hard tools, molds and wear-resistance parts.

This is the first time micro features are successfully fabricated using WC-Co without post-processing (infiltration, machining) and without the help of additional binding material (such as Cu, Ni, Fe).

The purpose of this paper is to propose and evaluate the selection of materials for the selective laser sintering (SLS) process, which is used for low-volume production in the engineering (e.g. light weight machines, architectural modelling, high performance application, manufacturing of fuel cell, etc.), medical and many others (e.g. art and hobbies, etc.) with a keen focus on meeting customer requirements.

The work starts with understanding the optimal process parameters, an appropriate consolidation mechanism to control microstructure, and selection of appropriate materials satisfying the property requirement for specific application area that leads to optimization of materials.

Fabricating the parts using optimal process parameters, appropriate consolidation mechanism and selecting the appropriate material considering the property requirement of applications can improve part characteristics, increase acceptability, sustainability, life cycle and reliability of the SLS-fabricated parts.

The newly proposed material selection system based on properties requirement of applications has been proven, especially in cases where non-experts or student need to select SLS process materials according to the property requirement of applications. The selection of materials based on property requirement of application may be used by practitioners from not only the engineering field, medical field and many others like art and hobbies but also academics who wish to select materials of SLS process for different applications.

This study/paper aims to investigate the erosion wear performance of Ni-based coatings [Ni-Cr-O and NiCrBSiFe-WC(Co)] under sand-water slurry conditions.

A high-velocity oxy-fuel (HVOF) process was used to deposit the Ni-based coatings [Ni-Cr-O and NiCrBSiFe-WC(Co)] on the surface of stainless steel (SS 316L) substrate. A Ducom TR-41 erosion tester was used to conduct the tribological experiments on bare/HVOF coated SS 316L. The erosion wear experiments were carried out for different time durations (1.30-3.00 h) at different impact angles (0-60°) by running the pot tester at different rotational speeds (600-1,500 rev/min). The solid concentration of sand slurry was taken in the range of 30-60 Wt.%. The surface roughness of Ni-based coated surfaces was also measured along the transverse length of the specimens.

Results show the arithmetic mean roughness (Ra) values of Ni-Cr-O and NiCrBSiFe-WC coated SS-316L were 7.04 and 6.67 µm, respectively. The erosion wear SS-316L was almost 3.5 ± 1.5 times greater than that of the NiCrBSiFe-WC coatings. NiBCrSi-WC(Co) sprayed SS-316L showed lower erosion wear than Ni-Cr-O sprayed SS-316L. Microscopically, the eroded Ni-Cr-O coating underwent plowing, microcutting and craters. Ni-Cr-O coating have shown the ductile nature of erosion wear mechanism. NiBCrSi-WC(Co) surface underwent craters, plowing, carbide/boride pullout, fractures and intact. Erosion wear mechanisms on the eroded surface of NiBCrSi-WC(Co) were neither purely ductile nor brittle.

It is a useful technique to estimate the erosion wear of hydraulic machinery coated with Ni-based coatings imposed under mining conditions.

The erosion wear performance of HVOF-sprayed Ni-Cr-O and NiCrBSiFe-WC(Co) powders was investigated through extensive experimentation, and the results are well supported by scanning electron micrographs and 3D topology.

The purpose of this study is to verify how the carbon doping of the WC-Co cemented carbide (CC) affected their structure before their processing by hot isostatic pressing (HIP) technology.

The samples for this experiment were fabricated by selective laser melting technology (SLM) using a YAG fiber laser with a power of P = 40 W and a scanning speed of 83 mm/s. The subsequent carbon doping process was performed in a chamber furnace at 900 0 C for 1, 4 and 12 h. The HIP was performed at 1,390°C and pressures of 40 MPa, 80 MPa and 120 MPa. The changes induced in the structures were evaluated using X-ray diffraction and various microscopic methods.

X-ray diffraction analysis showed that the structure of the samples after SLM consisted of WC, W₂C, Co₄W₂C and Co phases. As a result of the increase in the carbon content in the structure of the samples, the transition carbide W₂C and structural phase Co₄W₂C decayed. Their decay was manifested by the coarsening of the minor alpha phase (WC), which occurred both during the carburizing process and during the subsequent processing using HIP. In the samples in which the structure was carburized prior to HIP, only the structural phases WC and Co were observed in most cases.

The results confirm that it is possible to increase the homogeneity of the CC structure and thus its applicability in practice by additional carburization of the sample structure with subsequent processing by HIP technology.

This paper aims to investigate the effect of coating microstructure, mechanical and oxidation property on the tribological behaviour of low-pressure plasma spraying (LPPS) tungsten carbide/cobalt (WC-Co) coatings.

WC-12Co and WC-17Co coatings were deposited via the LPPS spraying method. Tribological tests on the coatings were performed using a high-temperature ball-on-disc tribometer at temperatures from room temperature (RT, approximately 25 °C) up to 800 °C in ambient air.

WC-12Co coating contained brittle phases, pores and microcracks, which led to the low hardness, and finally promoted the splat delamination and the carbide debonding during wear. WC-17Co coating had higher cobalt content which benefited the coating to contain more WC particles, less brittle phases, pores and nearly no microcracks, and resulted in the high hardness and better wear resistance. Higher cobalt content also decelerated the oxidation rate of the coating and promoted the formation of cobalt oxides and CoWO4, which were able to maintain the load-bearing capacity and improve the tribological behaviour of the coating below 650°C. Above 650°C, the increase of oxidation degree and the decrease of mechanical property deteriorated the wear resistance of coatings.

The LPPS WC-Co coating with higher cobalt content had better tribological properties at different temperatures. The LPPS WC-Co coatings should not be used as wear-resistant coatings above 650 °C.

This paper provides an overview of the different binding mechanisms in selective laser sintering (SLS) and selective laser melting (SLM), thus improving the understanding of these processes.

A classification of SLS/SLM processes was developed, based on the binding mechanism occurring in the process, in contrast with traditional classifications based on the processed material or the application. A broad range of commercial and experimental SLS/SLM processes – found from recent articles as well as from own experiments – was used to explain the different binding mechanism categories.

SLS/SLM processes can be classified into four main binding mechanism categories, namely “solid state sintering”, “chemically induced binding”, “liquid phase sintering – partial melting” and “full melting”. Most commercial processes can be classified into the latter two categories, which are therefore subdivided. The binding mechanism largely influences the process speed and the resulting part properties.

The classification presented is not claimed to be definitive. Moreover some SLM/SLM processes could be classified into more than one category, based on personal interpretation.

This paper can be a useful aid in understanding existing SLS/SLM processes. It can also serve as an aid in developing new SLS/SLM processes.

The purpose of this study is to develop a homogenization approach that ensures both high accuracy and time-efficient solution for elastic-plastic functionally graded composites.

The paper presents a novel two-stage hybrid homogenization approach that combines advantages of the mean field homogenization and homogenization based on the finite element method (FEM). The groundbreaking nature of the developed approach is associated with division of the hybrid homogenization procedure into two stages, which allows to very efficiently determine the solution for arbitrary volume fraction of the reinforcement. This paper concerns also on modelling of composites with randomly distributed prolate and oblate particles. For this purpose, the hybrid homogenization was implemented in the framework of the discrete orientation averaging procedure involving pseudo-grain discretization method.

Agreement between the results obtained using the proposed approach and the standard FEM-based homogenization is very good (up to the volume fraction of 0.3).

The proposed two-stage homogenization approach allows to obtain the solution for materials with arbitrary volume fraction of the reinforcement very efficiently; therefore, it is highly beneficial for the two-scale modeling of nonlinear functionally graded materials and structures.

This paper aims to investigate the flexural properties i.e. the flexural strength and the flexural modulus under the influence of selected input variables, namely; fiber type, fiber loading and fiber size in fabricated natural fiber polymeric composites through using Taguchi’s design of experiment methodology.

The Taguchi’s design of experiment approach has been used to scheme a suitable combination to fabricate the polymeric composites. Pure polypropylene (PP) has been chosen as a matrix material, whereas two types of fibers, namely; wood powder (WP) i.e. sawdust and rice husk powder (RHP), have been used as a reinforcement in the matrix. Microstructure analysis of fabricated and tested samples has also been evaluated and analyzed using a scanning electron microscope. This analysis has divulged that at moderate fiber size and higher fiber loading, no gap or cavities presented between the fillers and matrix particles, which illustrates the good interfacial bonding between the materials.

The flexural strength of the wood powder pure polypropylene (WPPP) composite decreases if the fiber content gets increased beyond 20 Wt.%. In addition, the flexural strength of hybrid composite (WPRHPPP) has been revealed to get improved more in comparison to composites with single fiber as reinforcement. Furthermore, the flexural modulus of WPPP composite has also increased with the increase in fiber loading. It has been concluded that reinforcement size plays an imperative role in influencing the flexural modulus. The optimum parametric setting for the flexural strength and the flexural modulus has been devised as; fiber type – WPRHP, fiber loading – 10 Wt.% and fiber size – 600 µm; and fiber type – WP, fiber loading – 30 Wt.% and fiber size – 1,180 µm, respectively. The microstructure images clearly revealed that during conducted flexural tests, some particles get disturbed from their bonded position that mainly represents the plastic deformation.

The fabricated polymer materials proposed in the research work are green and environmentally friendly.

The natural fiber-based composites are possessing wide-spread requirements in today’s competitive structure of manufacturing and industrial applications. The fabrication of the natural fiber-based composites has also been planned through the designed experiments (namely; Taguchi Methodology- L₉ orthogonal array matrix), which, further, makes the analysis more fruitful and qualitative too. The fabricated polymer materials proposed in the research work are green and environmentally friendly. Shisham WP has been rarely used in the past researches; therefore, this factor has been included for the present work. The injection molding process is used to fabricate the three different polymer composite by varying the fiber weight percentage and fiber size.

The main objective of this experimental work is to analyze and measure the form tolerances namely flatness and squareness while machining a meso deep hole in EDM on Inconel-718 material plate.

The experiments were performed on 15 amps rated SPARKONIX-EDM as per DOE (design of experiments). Kerosene was used as a dielectric along with constant pressure of 0.2 kg/cm² for all trial runs. The currents T_on and T_off were selected as process constraints to conduct experimental trials. The MRR, EWR, machining time and form tolerances were considered as output responses. The experimental outcomes were optimized by hybrid optimization using Taguchi and GRA (grey relational analysis) method.

The EDM process parameters for Ni-based super alloy namely Inconel-718 had optimized by using GRA method coupled with Taguchi method. The optimum solution has been calculated for MRR, EWR, machining time and form tolerances namely squareness and flatness. The optimized parameters for the output responses in EDM process are Peak current (Ip) 12 Amps, 400 µs T_on (pulse on time) and 10 µs T_off (pulse off time). An attempt had also been made to attain Max. and Min. Evaluation of MRR and form tolerances, respectively. The attained optimum outcomes had also been examined through a real experiment and established to be satisfactory.

This article will facilitate the defense, aerospace and EDM industries to improve their productivity with closer tolerances.

The optimized parameters by multi-parametric optimization showed the considerable improvement in the process and will facilitate the defense, aerospace and EDM industries to improve their productivity with closer tolerances.