Ali Samer Muhsan

Role of Debinding to Control Mechanical Properties of Powder Injection Molded 316L Stainless Steel

316L stainless steel is widely used in various industries due to low cost, ease of availability and exceptional combination of mechanical properties along with corrosion resistance as compared to the other available metal alloys. In powder injection molding, debinding is very critical step and improper debinding can change the final properties dramatically. In the present study, affects of debinding on mechanical properties of powder injection molded 316L stainless steel were studied. The prepared feedstocks were molded according to MPIF 50 standard using vertical injection molding machine (KSA100). The plastic binder was removed at 450°C from the molded test samples using two different furnaces i.e. commercial and laboratory furnace followed by the sintering in vacuum, hydrogen, mixture of H2 and N2 (9:1) and nitrogen at 1325°C for 2hr with post sintering cooling rate 3°C/min . Test samples debound in commercially available furnace showed 97% densification and higher mechanical properties. The corrosion resistance was reduced due to presence of residual carbon during thermal debinding. The presence of carbon and formation of carbides and nitrides were confirmed by XRD and microstructural analysis. The results showed that the test samples debound in commercial furnace showed brittle behavior due to the presence of carbides and nitrides. Test samples sintered in N2 showed 96.3% density and tensile strength 751MPa. This value of strength is twice as compared to the sample debound in laboratory furnace followed by the sintering in vacuum. The achieved mechanical properties in vacuum sintered samples were comparable to the wrought 316L stainless steel (according to ASTM standard).

Rheological Behavior of Carbon Nanotubes / Copper Feedstocks for Metal Injection Molding

Metal injection molding (MIM) technology is known for its ability of producing near net shape components. This study presents the results of flow behavior of multi-walled carbon nanotubes (MWCNTs) reinforced copper composites mixes. The solid loadings in the copper mixes were investigated in the ranges of 55-61 V% using a binder. Copper mixes and copper/MWCNTs were compounded using a Z-blade mixer for homogenous dispersion of solids in the binder. Results identified a mix containing 59 V% copper suitable for substitution of MWCNTs. The flow properties were measured using a capillary rheometer in the shear rate range expected to occur during metal injection molding. An increasing trend in viscosity of the copper mixes with powder loading was noted. Copper/MWCNTs composite mixes showed viscosity more than 1000 Pa.s perhaps due to addition of MWCNTs and increasing trend in viscosity of copper/MWECNTs was recorded. The results of flow data showed that all copper composite mix containing up to 10 Vol.% MWCNTs were successfully injection molding and test samples were produced.

Flow Behavior of Cu/CNTs Feedstocks for Powder Injection Molding

Abstract— In this study, the flow behavior of multi-walled carbon nanotubes (CNTs) reinforced copper matrix feedstocks isp resented. The solid loadings in the copper feedstock were investigated in the ranges of 55-61 Vol. % using binder. Pure copper (Cu) and Cu/CNTs feedstocks were compounded using internal mixer machine for homogenous dispersion of solids in the binder. The flow behavior was measured using a capillary rheometer in the shear rate range expected to occur during powder II.injection molding. An acceptable increasing trend in viscosity of the copper feedstock with powder loading was recroded. Cu/CNTs composite feedstocks showed viscosity more than 1000 Pa.s which is most probably due to the addition of CNTs and increasing trend in viscosity of Cu/CNTs was noted as well. The results also identified that the feedstock containing 59 vol. % copper was most suitable for substitution of CNTs in Cu feedstock.

Effects of Residual Carbon on Microstructure and Surface Roughness of PIM 316L Stainless Steel

Powder injection molding (PIM) offers an attractive method for producing smart and intricate shapes components. PIM process is cost effective and equally applicable for metals and ceramics. Debinding process is the most critical step among all PIM steps and any residual during debinding can change the composition of sintered product resulting change in final properties. In this research work, the injection molded samples were thermally debound and sintered in various atmospheres. The results showed that the sintered samples with improper thermal debinding resulted the carbide formation at the surface and across the grain boundaries that caused to increase the roughness value.

Effect of CNTs dispersion on the thermal and mechanical properties of Cu/CNTs nanocomposites

Modified technique of metal injection molding (MIM) was used to fabricate multiwalled carbon nanotube (CNT) reinforced Cu nanocomposites. The effect of adding different amount of CNTs (0-10 vol.%) on the thermal and mechanical behaviour of the fabricated nanocomposites is presented. Scanning electron microscope analysis revealed homogenous dispersion of CNTs in Cu matrices at different CNTs contents. The experimentally measured thermal conductivities of Cu/CNTs nanocomposites showed extraordinary increase (76% higher than pure sintered Cu) with addition of 10 vol.% CNTs. As compared to the pure sintered Cu, increase in modulus of elasticity (Youngs modulus) of Cu/CNTs nanocomposites sintered at 1050°C for 2.5 h was measured to be 48%. However, in case of 7.5 vol.% CNTs, Youngs modulus was increased significantly about 51% compared to that of pure sintered Cu.

Uniform Dispersion of Multiwalled Carbon Nanotubes in Copper Matrix Nanocomposites Using Metal Injection Molding Technique

This work presents a novel fabrication approach of multiwalled carbon nanotubes (MWNTs) reinforced copper (Cu) matrix nanocomposites. A combination of nanoscale dispersion of functionalized MWNTs in low viscose media of dissolved paraffin wax under sonication treatment followed by metal injection molding (MIM) technique was adopted. MWNTs contents were varied from 0 to 10 vol.%. Information about the degree of purification and functionalization processes, evidences on the existence of the functional groups, effect of sonication time on the treated MWNTs, and microstructural analysis of the fabricated Cu/MWNTs nanocomposites were determined using TEM, EDX, FESEM, and Raman spectroscopy analysis. The results showed that the impurities of the pristine MWNTs such as Fe, Ni catalyst, and the amorphous carbon have been significantly removed after purification process. Meanwhile, FESEM and TEM observations showed high stability of MWNTs at elevated temperatures and uniform dispersion of MWNTs in Cu matrix at different volume fractions and sintering temperatures (950, 1000 & 1050°C). The experimentally measured thermal conductivities of Cu/MWNTs nanocomposites showed remarkable increase (11.25% higher than sintered pure Cu) with addition of 1 vol.% MWNTs, and slight decrease below the value of sintered Cu at 5 and 10 vol.% MWNTs.

Fabrication and Microstructural Analysis of CNTs Reinforced Copper Matrix Nanocomposites via MIM Technique

Carbon nanotubes (CNTs) reinforced copper (Cu) matrix nanocomposites prepared via advanced fabrication method is presented. Functionalization and ultrasonication processes have been applied to enhance the dispersion of purified CNTs and creates sidewalls groups that have the potential to bond CNTs to the metal matrix. The main part of this approach was metal injection molding (MIM) technique, which is a combination of powder metallurgy and plastic injection molding technique. Preparation of MIM feedstock required a melting and mixing process of binder system (polymers) with the solid loading, which has been carried out using a twin screw rotor machine. This machine provides a viscous media of the molten binder with high shear forces that allow the additives (carbon nanotubes/copper powder) to be mixed properly and exfoliate the CNTs clusters with uniformdispersion inside the Cu matrix. Subsequently, to prove our expected results, observation tests of TEM, SEM, FESEM and CNTS were employed and discussed literally.

Graphene modified FTO/TiO2 interface photoelectrode for improved performance of dye sensitized solar cells

The microstructure of photoelectrode plays a crucial role in the performance of Dye Sensitized Solar Cells (DSSCs). The uneven morphology of FTO (Fluorine doped tin oxide) glass and high porosity of TiO2 layer will produce defects such as tiny gaps, pores and cavities in FTO/TiO2 interface which allows for direct penetration of the electrolyte to the surface of FTO, leading to the recombination of electrons. To address this issue some work has been conducted to functionalize FTO glass with graphene because of its exceptional mobility and transparency. However, this approach is not feasible as graphene nanosheets is economically quite expensive. Therefore, in the current study, graphene nanosheets is replaced with graphene nanoplatelets (GNPs) in order to modify the FTO/TiO2 interface by providing conducting bridges to photo-injected electrons and impede the excessive penetration of the electrolyte. The conversion efficiency for GNP modified interface was found to be 2.32 % (active area of 1 cm2), which is...

Defect Analysis of 316LSS during the Powder Injection Moulding Process

Austenitic Stainless Steel Has a FCC Structure at Room Temperature and the Temperature Range of the Austenite Phase Depends upon its Composition. 316L SS Is Widely Used in Medical, Marine, Industrial, Sporting and Aerospace Applications due to its Excellent Combination of Mechanical Properties and Corrosion Resistance. this Study Presents the Defects Observed during Optimization of the Processing Parameters for the Fabrication of Powder Injection Molding (PIM) of 316L SS Parts. in this Study, Five Formulations of Feedstock Containing 60-71vol% of Metal Powder Were Prepared Using a Wax-Based Binder. Green Samples Were Injection-Moulded, Followed by Binder Removal by Solvent and Thermal Means. Paraffin Wax (major Binder) Was Extracted at Various Temperatures in Order to Determine the Solvent Extraction Temperature. the Thermal De-Binding Was Performed Successfully at a Temperature of 450°C by Varying the Heating Rate from 1°C/min -10°C/min. SEM Results Showed Complete Removal of the Plastic Binder. Test Samples Were Sintered at Various Temperatures and Atmospheres. the Defects Observed during Solvent Extraction Were Swelling, Cracks and, at the Thermal De-Binding Step, Collection of Binder, Swelling and Holes. Sintered Samples Showed a Loss of Dimensional Control. these Types of Defect Were Considered to Be due to Inappropriate Heating Rates, Temperature and Dwell Time at each Process Step.

Nano Additives in Water Based Drilling Fluid for Enhanced-Performance Fluid-Loss-Control

Drilling fluid which is also known as drilling mud is a crucial element in oil and gas exploration process as it used to aid the drilling of boreholes into the earth. Among other functions, drilling fluid needs to carry drill cuttings to the surface of the well, support the walls of the well bore, provide hydrostatic pressure to prevent formation fluids from entering into the well bore, cool and lubricate the drill bit, prevent drill-pipe corrosion, facilitate the attainment of information about the formation being drilled, and create a thin low-permeability cake that protects permeable production formations. Water-based mud (WBM) is the most common drilling fluid used in oil industry. WBM is an expensive complex chemical system that is usually mixed with filtration-loss-prevention additives such as clay, lignite, or organic polymers, with bentonite clays being very common to control the fluid-loss during drilling process. These traditional additives are able to give an average fluid loss of 7.2 mL over 30 min and leaving a filter cake ∼280 μm thick. Graphene, as a single layer of graphite which is also considered nano-additive, has become the subject of much research interest for its unique materials properties. A pristine graphene monolayer has a theoretical surface area of 2965 m2/g and has been shown to form a membrane impermeable even to helium gas. This work presents the recent progress of using nano-materials such as graphene as an additive in WBM. Most recent report showed that graphene has the potential to decrease the fluid loss by ∼15–20% (due to its large surface area with very thin 2D layer, only 1 atom thick) compared to that of WBM with conventional additives, and to reduce the filter cake thickness up to ∼20–50 μm, which in turn can help to increase the oil production rate. In addition, adding graphene to WBM solutions is expected to lead to greater shear thinning and higher temperature stability compared to clay-based fluid loss additives.