Volkan Gunay

Effect of sintering parameters on mechanical properties of injection moulded Ti–6Al–4V alloys

Abstract This paper describes the microstructural and mechanical properties of injection moulded Ti–6Al–4V parts. Ti–6Al–4V powder was injection moulded with wax based binder. The critical powder loading for injection moulding was 67·5 vol.-% for feedstock. Binder debinding was performed with solvent and thermal method. After debinding the samples were sintered at different temperatures and times in vacuum atmosphere (10−4 torr). Metallographic studies were conducted to determine to extend densification and the corresponding microstructural changes. The results show that Ti–6Al–4V powder could be sintered to a maximum 99% of theoretical density. Maximum ultimate tensile strength and hardness were obtained 704 MPa and 38·6 HRC at 1275°C for 10 h.

Effect of Fiber Orientation on Scratch Resistance in Unidirectional Carbon-Fiber-Reinforced Polymer Matrix Composites

Polymer composites have been widely used in industrial applications because of their high-specific strength and modulus. During their maintenance and service life small scratches can be formed on the surface of the composite material. These small scratches can result in crack initiation causing material failure and also some esthetic defects. When we consider that polymer composites may have various fiber orientations, it is possible to develop a remarkable increase in their scratch resistance. For this reason it is necessary to investigate the effect of fiber orientation on scratch resistance for polymer composites. In this study, scratch resistance of continuous carbon-fiber-reinforced polyetherimide composites were investigated as a function of fiber orientations by means of CSM microscratch tester machine. During the experiments the relation between the scratch resistance and operational parameters are determined as a function of scratch hardness, penetration depth, and coefficient of friction.

Self Cleaning Photoactive TiO2 Coatings on SLS Glasses by Sol-Gel Dip Coating

Self-cleaning and anti-fogging coatings can be realized utilizing TiO2 thin films on various substrates. Photoactive TiO2 films exhibit strong oxidation power to breakdown organic compounds when illuminated by UV. TiO2 thin films possess photo-induced hydrophilicity, which is required for self-cleaning properties. They give optical quality with high reflectivity when coated on glass. In the present study, commercial float glass samples were coated by using sol-gel dip-coating process. Coated glasses were heat treated at 400 o C for obtaining the desired properties. In order to monitor the photoactivity of the films, the decrease in the absorption of the aqueous solution of rhodamine B was measured after light irradiation of film surfaces as a function of time. The photoactivity of the films was measured also through the decomposition of stearic acid applied onto TiO2 films. In this study, the effects of film thickness and mean crystallite size on the photoactivity were given and discussed.

Mechanical Properties of Powder Injection Molded Ni-Based Superalloys

This paper describes the microstructural and mechanical properties of powder injection moulded (PIM) Ni based superalloys. Ni-based superalloys were mixed with a polymeric binder (paraffin wax, carnauba wax, stearic acid and PP) and injection moulded as standard tensile bars. The critical powder loading for injection moulding were 62.5 vol. % for standard samples. Binder removal, debinding, was performed using a two-step solvent/thermal method. After debinding the samples were sintered at 1100°C and at 1285°C under high level vacuum. Metallographic studies were conducted to reveal the extent of densification and the corresponding microstructural changes. Ni 718, Ni 625 and Nimonic90 samples achieved high sintered densities via supersolidus liquid phase sintering. The mechanical properties of Ni 718, Ni 625 and Nimonic90 are determined and compared with the properties of previously reported studies on similar PIM materials.

Influence of TiC, TiN and TiC(N) additions on sintering and mechanical properties of injection moulded titanium based metal matrix composites

Abstract Titanium (Ti) matrix composites based on Ti and reinforced with TiN, TiC and TiCN particles, were processed following a powder injection molding route: mixing, preparation of feedstock, moulding, debinding and sintering for full densification. The Ti and ceramic powders were dry mixed and molded using a wax based binder. The critical powder loading for injection molding was 55 vol.-% for all samples. Binder debinding was performed using solvent and thermal methods. Following the debinding stage, the samples were sintered for full densification at 1300°C for 2 h in vacuum. Metallographic studies were conducted to investigate densification and the corresponding microstructural changes. The sintered samples were characterized by measuring tensile strength, elongation and hardness. All powders and fracture surfaces of sintered samples were also examined using scanning electron microscope techniques. The sintered densities of injection molded Ti and composites samples were changed with increasing amount of ceramic additions. The addition of TiN, TiC and TiCN improves the densities, tensile strength and hardness.

Hydrophobic (Water Repellant) Silica Films Having High Heat Resistance by Sol-Gel Dip Coating

Water repellant glasses fabricated by coating a water repellant film maintaining the original optical property of the glass have wide variaty of applications. Sol-gel method is widely used to produce films on glasses. High heat resistance and high temperature stabilities of these water repellant films were desirable in many applications. Water repellant silica films containing various amount of F-silane (0-4 wt%) were formed on commercial float glass samples by sol-gel dip coating at room temperature. Initial water repellency was measured by measuring the wetting (contact) angle of water droplets on coated glasses. The effects of F-silane contents and heat-treatments up to 400 0 C were studied. Wetting angle of the initial coatings were around 100-105 0 and these angles were nearly stable up tu 350 0 C but above this temperature the wetting angles dropped to 70-75 0 . It was observed that the wetting angles of the coatings , was not affected by F-silane content. There was not much differences in wetting angles when the F-silane content was 0.5 or 4 wt%. High temperature stability of the water repellant glasses related directly to the removal of Fcontaining organic part of the coating at high heat treatment temperatures namely after 350 0 C.

The Effect of Fused Magnesia Addition on the Properties of Chamotte Refractories

This investigation reports the effect of magnesia addition on the properties of chamotte (fireclay) refractories. Five compositions were prepared containing 0, 3, 5, 7 and 9 w/o fused magnesia addition. Before mixing, powders were prepared by grinding and milling of fireclay and magnesia refractory bricks to pass through 300 micron. Five samples were prepared for each composition and all samples were shaped using uniaxial pressing as rectangular bar. Sintering was carried out at 1400 °C for one hour in air. Characterisation tests were performed including firing shrinkage, bulk density, apparent porosity and flexural strength test at room temperature. Microstructural examination by optical microscopy, and phase analysis by XRD were also carried out. All fused magnesia added samples except for 9 w/o were generally improved physical properties of chamotte refractory. Comparatively, better properties such as higher bulk density, lower porosity, and higher flexural strength were obtained with 3 w/o fused magnesia addition among all samples studied.

Numeric Simulation of the Penetration of 7.62 mm Armour Piercing Projectile into Ceramic/Composite Armour

A numerical study has been carried out to design armour system which consists of 99.5 % alumina ceramic tiles backed by plain weave S2-glass/epoxy laminated composite plates when subjected to high velocity impact of a 7.62 mm armour piercing (AP) projectile. The explicit three-dimensional finite element code LS-DYNA was used in the analysis of the problem. A plastic-kinematic hardening model; MAT-03, the Johnson-Holmquist-Ceramic model; MAT-110 and newly developed composite damage model namely MAT-162 implemented in LS-DYNA were used in order to simulate behaviours of projectile, ceramic and composite layers respectively in the numerical model. Three configurations with different composite backing plate thicknesses were considered in the numerical analyses in order to defeat a 7.62 mm AP projectile. Numerical results showed that among the investigated armour panels the best multi-hit ballistic performance was attained with configuration 3 which maintained ballistic protection with a minimal damage to the composite backing and much smaller back face signature.

Hybrid Nano-Composite Sol-Gel Coatings on Glass

Nano-composite sol-gel coatings on commercial glasses were applied by dip coating. Coating solution contained TEOS and GLYMO together with solvent, water and acid as a catalyst. Withdrawing rates of 2, 6 and 12 inch/min were applied and heat-treatment conditions were 200 o C for 1 hour in static air. Abrasion resistance, chemical resistance test with HCl, adhesion tests such as cross hutch cutter and HF were carried out and optical properties were measured in order to study the effects of these hard nano-composite coatings on glass. Results showed that the abrasion resistances were very high on Taber abrasion tests comparable to that of glass. Also optical properties of coated glasses were very similar to those of uncoated glasses. Only there was a small increase on transmission and this is a desirable optical property in glass applications. Introduction Nanocomposites with metals, semiconductors or ceramics are of interest since special properties related to solid state materials (e.g., refractive index of ceramics, quantum confinement of metals and semiconductor colloids) can be used for optical purposes. The sol-gel process is a suitable means to synthesize inorganic-organic composite material since the inorganic backbone can be built up by a low temperature process, and organics can survive processing. The use of organosilanes is one interesting means to combine inorganic with organic structures [1]. For optical applications, transparent and homogeneous coatings can be made by using sol-gel derived hybrid nanocomposite coating solution. It is necessary to control structure formation, especially with respect to the distribution or aggregation of inorganic network forming units and organics [2]. In this study, soda-lime-silica (SLS) glasses were coated with an inorganic-organic silica based solution and optical, chemical and mechanical properties were investigated. Test method and its requirements, which are used for observing abrasion resistance, are defined in ASTM D 1044-99 [3]. Adhesion test was made according to BS EN ISO 2409 [4] and ASTM D3359-B [5] standards. Experimental SLS glass samples which have 3 mm thickness and 10 × 10 cm dimensions were used. The coatings were made by using inorganic-organic silica based solution. Coating solution was prepared by stirring TEOS (tetraethyl orthosilicate), hydrochloric acid, ethanol and de-ionised water for 2 h at room temperature. After stirring, 0.002 mol GLYMO (3-glycidoxypropyltrimethoxysilane) was added and stirred again for 24 h at the same conditions. Glass samples were coated with 3 different withdrawal rates by using a Chemat Dip Master 201 instrument. Coated samples were heated at 200 0 C for 1 hour. Coating thicknesses were measured with Tencor Alpha Step 500 instrument. The optical data were collected with PERKIN ELMER UV/VIS/NIR LAMBDA 900 spectrophotometer. For evaluating abrasion resistance, Taber 5151 Abraser and BYK Gardner Haze-Gard Dual were Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 395-398 doi:10.4028/www.scientific.net/KEM.264-268.395

Preparation and Characterization of Sol-Gel Derived 4%La2 O3-Al2O3 Ceramic Membrane on Clay-Based Supports

In this work, γ-Al 2O3 membrane layer (4 wt % La 2O3 + 96 % Al 2O3 ) was coated on the clay based porous support by using the sol-gel coating. The coating solution was prepared by using boehmite (AlOOH), La-nitrate (La 2(NO 3)3.6H 2O), PVA, distilled water and HNO 3. The thickness of the γ-Al 2O3 membrane layer was between 5-7 μm. Two unprocessed clay samples which were supplied from Kutahya and Balokesir regions, were used to produce supports for the membranes. Porosities of the supports were varied from 25 to 40% depending on sintering temperatures. Mean pore diameter of the supports were between 0.01-1μm. The mean pore diameter of 4wt%La 2O3 - Al 2O3 membrane layer was around 11 nm and total pore area was 113 m 2 / g at 1000 0 C for 1 hour.