Papers by Keyword: Cermet

Abstract: Cemented tungsten carbides have been paid much attention due its better mechanical properties with excellent combination of hardness and toughness characteristics. The hard WC particles in the coating provide hardness and wear resistance, while the ductile binder such as Co and Ni contribute to toughness and strength. WC-17wt.% Co and WC-9wt.% Ni powders have been sprayed by the HVOF method to form coatings approximately 300μm and 150μm thick onto AISI 1018 steel substrate. Both coatings have been prepared and supplied by an external vendor. The coatings were examined using optical microscope (OM), scanning electron microscope (SEM), and X-Ray diffraction (XRD). The hardness of both coatings were also measured using Vickers micro-hardness tester. The microstructure of the coatings has been analyzed and found to consist of WC, brittle W₂C phase, metallic W phase, and amorphous binder phase of Co and Ni. It is found that WC-Ni has a higher hardness value compared to WC-Co due to high porosity distribution.

Abstract: Behavior of the material adhered to the cutting edge of a cermet insert was evaluated based on the profile of the machined surface in continuous turning of an austenite stainless steel SUS304. Height of the adhesion material decreased rapidly with increase of the cutting speed from 10m/min to 20m/min. The behavior of the adhered material was more stable than we expected. The adhered layer near the cutting edge was very stable, while the growth or breakage of the adhered material happened on the surface of the stable layer.

Abstract: Metal-ceramic composite or cermet coatings have become popular due to their enhanced wear and corrosion resistance properties. Cermet consists of ceramic particulate embedded in a metallic binder. WC-Co coatings are often used in applications that require wear resistance, but there are many applications in which thermally sprayed coatings have been deposited on components that operate under both abrasive and corrosive condition. Thus, in this study, the corrosion behavior of WC-12wt%Co in different electrolyte has been evaluated. Electrochemical test has been done in three electrolytes namely 0.5 M hydrochloric acid, HCl, 0.5 M sulfuric acid, H₂SO₄ and 0.5 M sodium hydroxide, NaOH. It is found that corrosion potential of this coating in acidic environment is more positive compares to in alkaline environment. Both in acid and alkaline electrolyte, binder dissolution were preferential. It may be concluded that this coating have higher corrosion resistance in alkaline electrolyte than in acid electrolyte.

Abstract: TiC based cermet is a candidate material for alternatives of WC-Co used in tools/dies. Ordinary, Ni and Co, etc. are used as a metal binder of TiC based cermet. They are kinds of rare metals, therefore it is desired that metal binders are also replaced with the ubiquitous materials. FeAl intermetallic alloys are one of candidate materials of alternative rare metal binder made from ubiquitous materials. FeAl is well-known as an extremely resistance material to corrosion under oxidizing atmospheres, sulfidizing atmospheres, and in molten salts. Combination of intermetallic and carbide, the hardness is very high, but it would be brittle. In this work, TiC-FeAl alloys are made by wet milling and pulsed electric current sintering to improve transverse rupture strength while the hardness is kept. We achieved that TiC-40 vol. % (Fe-40 at. % Al) alloy with hardness of 17.7 GPa and T.R.S. of 1.9 GPa.

Abstract: With the aim of developing a durable tool for friction stir processing (FSP) of cast iron, the durability of a Ti (C,N)-Ni cermet tool has been investigated and compared with that of a WC-Co cemented carbide tool. Results of exposure tests in air revealed that the WC-Co cemented carbide sample oxidized rapidly above 973 K, whereas the cermet material showed little oxidization even after holding at a temperature of 1103 K. When these tools were used for the FSP of cast iron surfaces, it was found that an oxide layer of over 100 μm was generated on the lateral faces of the WC-Co cemented carbide tool after it was used to work a length of 400 mm. In contrast, a thin oxide layer of only 5 μm was generated after the cermet tool worked a length of 2400 mm. Cross sections of the iron casts (FC250) subject to FSP using these tools showed that in a bowl-shaped region approximately 1.5 mm deep the initial pearlite structures changed to martensite structures. The martensite structures in this region had a Vickers hardness of 600 to 800 HV, while that of the initial pearlite structure was about 280 HV.

Abstract: The fracture toughness and hardness of Ti (C_0.7N_0.3)-19Mo₂C-xNbC-24Ni cermets (x = 0, 5, 20) were studied. Fracture toughness of 5 NbC was the largest, and it of 20 NbC was the lowest. The microstructures of all the cermets consisted of Ti (C,N) and solid soluted Ti (C,N) hard phase, and Ni binder phase. The solid soluted Ti (C,N) surrounded Ti (C,N), namely, core-rim structures were observed in 0NbC and 5NbC. On the other hand, the isolated Ti (C,N) and solid soluted Ti (C,N) were observed in 20NbC, as a result of the phase separation between Ti (C,N) core and solid soluted Ti (C,N).

Abstract: The current study is focused on deposition of different carbide based powders as WC/10Co/4Cr, Cr3C2/25NiCr, CrC/37WC/18M using High Velocity Oxygen Fuel (HVOF) spraying technique onto the surface of low carbon steel substrates. The obtained coatings were characterized by means of X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) to study their phases and morphology. Hardness and porosity values of the coatings were also measured. The sliding wear behavior was evaluated using the pin-on-disk method and the corrosion resistance was determined by open cell potential measurements and salt spray tests. Comparative results of the investigated samples showed that the WC/10Co/4Cr coating had the best wear properties and the Cr3C2/25NiCr coating had the best corrosion resistance.

Abstract: The way is developed by the combined process of finishing machining. In this method, surface treatment is due to the combined effects of cutting tool and anodic dissolution of metal under the influence of an electric current in the electrolytic solution. Applying of this method allow the processing of aluminum and copper alloys to obtain higher quality parameters of the obtained surface, including special material.

Abstract: Compacts for the synthesis of composite zones in castings were obtained by cold pressing powders of the TiC reactants under a pressure of 250, 300, 500 and 600 MPa. The all compacts made under different pressures were placed in a mould cavity and poured with liquid unalloyed low-carbon steel. From the resulting casting, four composite zone A, B, C, D, produced in this casting by in situ method. In all composite zones, TiC and ferrite (αFe) were obtained. Additionally, in zones A, B and C the presence of graphite (C_gr) was also stated. The surface friction (S_f) of C_gr decreases in composite zones A ÷ D, while both the S_f of TiC and hardness VH30 increase in these zones with increasing compaction pressure of the reactants. Too low compaction pressure applied to the TiC reactants impedes the effective propagation of the reaction of synthesis.

Abstract: WC-5TiC-15Co cermets were prepared via novel technology – reactive sintering. In case of reactive sintering the elemental powders of tungsten, titanium, cobalt and carbon black are activated through ball-milling and then the synthesis of carbide occurs in the same cycle with the sintering of the cermet. Carbon content in initial powder mixture has crucial effect on properties of reactive sintered WC-based cermets. This paper investigates the erosion wear of the WC-5TiC-15Co cermets. Wear resistance dependent on the carbon content as well as wear mechanism of reactive sintered and conventional cermets are exhibited.