Abstract: Tungsten carbide is widely used as a tool material in metal manufacturing process. Since tungsten is typical rare metal, establishment of recycle process of tungsten carbide tools and restore into cemented carbide material bring great impact to metal manufacturing industry. Recently, recycle process of tungsten carbide has been developed and established gradually. However, the demands for quality of cemented carbide tool are quite severe because hardness, toughness, anti-wear ability, heat resistance, fatigue strength and so on should be guaranteed for precision machining and tool life. Currently, it is hard to restore the recycled tungsten carbide powder entirely as raw material for new processed cemented carbide tool. In this study, to suggest positive use of recycled tungsten carbide powder, we have tried to fabricate a carbon based sintered steel which shows reinforced mechanical properties with recycled tungsten carbide powder. We have made set of newly designed sintered steels. Compression test of sintered specimen in density ratio of 0.85 (which means 15% porosity inside) has been conducted. As results, at least 1.7 times higher in nominal strength in the amount of 7.0 wt.% was shown in recycled WC powder. The strength reached to over 600 MPa for the Fe-WC-Co-Cu sintered alloy. Wear test has been conducted by using ball-on-disk type friction tester using 5 mm diameter ball with normal force of 2 N in the dry conditions. Wear amount after 1,000 m running distance shows that about 1.5 times longer life was shown in designed sintered alloy. Since results of tensile test showed that same tendency in previous testing, it is concluded that designed sintered alloy can be used for several mechanical parts with special strength and anti-wear ability in relatively low cost due to recycled tungsten carbide powder.
Abstract: In this work, obtaining methods of ultrafine alumina
powdery composites and high temperature pressing technology of
matrix ceramic composites with different compositions have been
discussed. Alumina was obtained by solution combustion synthesis
and sol-gel methods. Metal carbides containing powdery composites
were obtained by homogenization of finishing powders in nanomills,
as well as by their single-step high temperature synthesis .Different
types of matrix ceramics composites (α-Al2O3-ZrO2-Y2O3, α-Al2O3-
Y2O3-MgO, α-Al2O3-SiC-Y2O3, α-Al2O3-WC-Co-Y2O3, α-Al2O3-
B4C-Y2O3, α-Al2O3- B4C-TiB2 etc.) were obtained by using OXYGON
furnace. Consolidation of powders were carried out at 1550-
1750°C (hold time - 1 h, pressure - 50 MPa). Corundum ceramics
samples have been obtained and characterized by high hardness and
fracture toughness, absence of open porosity, high corrosion
resistance. Their density reaches 99.5-99.6% TD. During the work,
the following devices have been used: High temperature vacuum
furnace OXY-GON Industries Inc (USA), Electronic Scanning
Microscopes Nikon Eclipse LV 150, Optical Microscope NMM-
800TRF, Planetary mill Pulverisette 7 premium line, Shimadzu
Dynamic Ultra Micro Hardness Tester DUH-211S, Analysette 12
Dynasizer.
Abstract: Ultrasonic machining is one of the most widely used non-traditional machining processes for machining of materials that are relatively brittle, hard, and fragile such as advanced ceramics, refractories, crystals, quartz etc. Present article has been targeted at investigating the impact of different experimental conditions (power rating, cobalt content, tool material, thickness of work piece, tool geometry, and abrasive grit size) on over cut in ultrasonic drilling of WC-Co composite material. Taguchi’s L-36 orthogonal array has been employed for conducting the experiments. Significant factors have been identified using analysis of variance (ANOVA) test. The experimental results revealed that abrasive grit size and tool material are most significant factors for over cut.
Abstract: In this paper, the effect of WC-12Co particle velocity in HVOF thermal spraying process on the coating thickness has been studied. The statistical results show that the spray distance and oxygen-to-fuel ratio are more effective factors on particle characterization and thickness of HVOF thermal spraying coatings. Spray Watch diagnostic system, scanning electron microscopy (SEM), X-ray diffraction and thickness measuring system were used for this purpose.
Abstract: High velocity oxygen fuel (HVOF) spray technique is one of the leading technologies that have been proposed as an alternative to the replacement of electrolytic hard chromium plating in a number of engineering applications. In this study, WC-Co powder was coated on AISI1045 steel using high velocity oxy fuel (HVOF) method. The sin2ψ method was used to evaluate the through thickness residual stress by means of XRD after mechanical layer removal process (only grinding). The average of through thickness residual stress using X-Ray diffraction was -400 MPa.
Abstract: In this project three type of tools, straight cylindrical, taper cylindrical and triangular tool all made of High speed steel (Wc-Co) used for the friction stir welding (FSW) aluminum alloy H20–H20 and the mechanical properties of the welded joint tested by tensile test and vicker hardness test. Besides, mentioned mechanical properties compared with each other to make conclusion. The result helped design of welding parameter optimization for different types of friction stir process like rotational speed, depth of welding, travel speed, type of material, type of joint, work piece dimension, joint dimension, tool material and tool geometry. Previous investigations in different types of materials work pieces; joint type, machining parameter and preheating temperature take placed. In this investigation 3 mentioned tool types that are popular in FSW tested and the results completed other aspects of the process. Hope this paper can open a new horizon in experimental investigation of mechanical properties for friction stir welded joint with other different type of tools like oval shape probe, paddle shape probe, three flat sided probe, and three sided re-entrant probe and other materials and alloys like titanium or steel in near future.
Abstract: An explicit axisymmetrical FE methodology is
developed here to study the particle temperature arising in WC-Co
particle on an AISI 1045 steel substrate. Parameters of constitutive
Johnson-cook model were used for simulation. The results show that
particle velocity and kinetic energy have important role in
temperature arising of particles.
Abstract: In this paper, the application of thermal spray
coatings in high speed shafts by a revolution up to 23000 RPM
has been studied. Gas compressor shafts are worn in contact
zone with journal therefore will be undersized. Wear
mechanisms of compressor shaft were identified. The
predominant wear mechanism is abrasion wear. The worn
surface was coated by hard WC-Co cermets using high
velocity oxy fuel (HVOF) after preparation. The shafts were in
satisfactory service in 8000h period. The metallurgical and
Tribological studies has been made on the worn and coated
shaft using optical microscopy, scanning electron microscopy
(SEM) and X-ray diffraction.
Abstract: In this paper, the techniques for estimating the
residual stress in high velocity oxy fuel thermal spray coatings have
been discussed and compared. The development trend and the last
investigation have been studied. It is seemed that the there is not
effective study on the effect of the peening action in HVOF
analytically and numerically.
Abstract: The mechanical and tribological properties in WC-Co
coatings are strongly affected by hardness and elasticity
specifications. The results revealed the effect of spraying distance on
microhardness and elasticity modulus of coatings. The metallurgical
studies have been made on coated samples using optical microscopy,
scanning electron microscopy (SEM).
Abstract: The mechanical and tribological properties in WC-Co
coatings are strongly affected by hardness and elasticity
specifications. The results revealed the effect of spraying distance on
microhardness and elasticity modulus of coatings. The metallurgical
studies have been made on coated samples using optical microscopy,
scanning electron microscopy (SEM).