Oxidation behavior of WC–Co hard metal with designed multilayer coatings by CVD
01 Mar 2012-International Journal of Refractory Metals & Hard Materials (Elsevier)-Vol. 31, pp 171-178
TL;DR: In this article, a multilayer coating composed of TiN, TiCN, α-Al 2 O 3 and κ-Al O 3 was designed and then deposited on WC-Co alloy by chemical vapor deposition (CVD) technique, the results showed that the oxidation resistance of WCCo alloy was improved markedly after deposition of multi-layer coatings.
Abstract: Multilayer coatings composed of TiN, TiCN, α-Al 2 O 3 and κ-Al 2 O 3 were designed and then deposited on WC–Co alloy by chemical vapor deposition (CVD) technique, the samples of WC–Co alloy with multilayer coatings were oxidized in the temperature range of 600 °C–950 °C for various times in a Muffle furnace, and weight gain was measured by electronic balance. Phase component and microstructure evolution of coating samples after oxidation were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the oxidation resistance of WC–Co alloy was improved markedly after deposition of multilayer coatings. The oxidation kinetics of multilayer coating samples obeyed linear law and diffusion-controlled parabolic law at different oxidation conditions. The oxidation product of coatings was rutile TiO 2 . The sample exhibited excellent oxidation resistance when the outermost layer was α-Al 2 O 3 , which was consistent to the results of apparent activation energy of oxidation reaction. The oxidation resistance of multilayer coatings was improved with the increase of thickness of κ-Al 2 O 3 layer. The κ-Al 2 O 3 transformed into α-Al 2 O 3 over 900 °C. The interface between TiN and TiCN disappeared in the coating sample without α-Al 2 O 3 and κ-Al 2 O 3 layer.
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TL;DR: In this article, the oxidation behavior of WC-12Co and electroless Ni/WC-Co coatings is investigated by Thermogravimetric analysis (TGA), X-Ray Diffraction (XRD), and scanning electron microscope (SEM).
57 citations
TL;DR: In this article, an Al-rich Ti005Al095N coating with a unique self-organized microstructure of alternating soft hexagonal (w) AlN and hard cubic (fcc) TiN nanolamellae synthesized by a low-pressure chemical vapor deposition (CVD) process is analyzed in terms of oxidation resistance, micro-structure and phase stability, hardness as well as residual stresses.
Abstract: The influence of microstructure on thermal and oxidation properties of Ti1-xAlxN hard coatings is not fully understood In this work, an Al-rich Ti005Al095N coating with a unique self-organized microstructure of alternating soft hexagonal (w) AlN and hard cubic (fcc) TiN nanolamellae synthesized by a low-pressure chemical vapor deposition (CVD) process is analyzed in terms of oxidation resistance, microstructure and phase stability, hardness as well as residual stresses Multiple coating samples on hard metal substrates were oxidized in ambient air for 1 h at temperatures in the range of 700–1200 °C Exceptionally good oxidation resistance up to 1050 °C was found, whereas above 1100 °C a localized surface degradation caused by the substrate–air interaction with very characteristic oxide blisters was observed A coating hardness of about 29 GPa remained in all unaffected surface areas for temperatures up to 1050 °C This is interpreted by the specific lamellae microstructure that retained a nanocomposite character even after lamellae partly decomposed during annealing Depth-resolved stress and phase characterization performed by cross-sectional X-ray nanodiffraction in the as-deposited Ti005Al095N revealed a strong compressive residual stress gradient of up to − 2 GPa at the coating surface which homogenized but remained still compressive after annealing at 1050 °C Finally, it is demonstrated that the unique dense nanocomposite microstructure is responsible for the superior oxidation behavior as well as high compressive stresses in the Ti005Al095N coating
48 citations
TL;DR: In this article, a new sintered composite cutting tool has been developed based on tungsten carbide matrix ligated with cobalt (WC-Co) additivated with tantalum carbide (TaC), TiC, TiC and niobium carbide(NbC) as grain growth inhibitors.
44 citations
TL;DR: In this article, the parabolic kinetics of high-temperature oxidation of titanium-tantalum carbonitride-based cermets with different Ti/Ta ratios were studied.
41 citations
Cites background from "Oxidation behavior of WC–Co hard me..."
...3 Although the oxidation kinetics of cemented carbides have been studied by some researchers [3, 14-20], published reports focusing on the oxidation kinetics of cermets are scarce [21, 22]....
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TL;DR: In this article, the high temperature oxidation behavior of HVOF-sprayed WC-12Co and WC-10Co-4Cr coatings was investigated using TGA for isothermal treatments in the range of 500-800°C for 3h.
Abstract: In this study, the high temperature oxidation behavior of HVOF-sprayed WC–12Co and WC–10Co–4Cr coatings were investigated. To explore the oxidation mechanism, thermo-gravimetric analysis (TGA) was applied for isothermal treatments in the range of 500–800 °C for 3 h. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to evaluate the structural changes and microstructural evolutions during oxidation tests. The TGA experiments showed negligible oxidation mass gains at 500 °C for both coatings. At higher temperatures, i.e. 700 and 800 °C, the oxidation mass gains of WC–12Co were found to be much higher than those for WC–10Co–4Cr coating, respectively. The higher oxidation resistance of WC–10Co–4Cr coating probably results from the formation of compact chromium oxide layers and higher MWO 4 type tungstate (M: Co and/or Cr) to tungsten trioxide (WO 3 ) ratios which provide lower porosity and consequently more efficient passivation effect against oxidation. The time dependent mass gain of WC–12Co coating obeys the linear law within temperature range of 600–800 °C with apparent oxidation activation energy of ~ 104 kJ/mol. As for the oxidation of WC–10Co–4Cr coating, a negligible deviation from linear law was observed possibly due to the presence of chromium oxide and higher tungstate to tungsten trioxide ratio which hinders the diffusion process through the scales compared with WC–12Co coating. The apparent activation energy for oxidation of the WC–10Co–4Cr coating was found to be ~ 121 kJ/mol.
39 citations
References
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TL;DR: In this paper, the thermodynamics of tungsten carbide oxidation reactions were calculated and the reaction kinetics of the alloys followed a complex behaviour. But, the results showed that the WC-16%Co alloy is oxidized to a lesser degree than the WC16%Ni alloy in the temperature range 650-800 °C.
Abstract: Oxidation of WC-16%Co, WC-8%Co-8%Ni and WC-16%Ni hard metals in the temperature range between 500 and 800 °C was investigated by TGA, XRD and SEM methods. The thermodynamics of tungsten carbide oxidation reactions was calculated. Oxidation kinetics of the alloys follows a complex behaviour. The WC-16%Co alloy is oxidized to a lesser degree than the WC-16%Ni alloy in the temperature range 650–800 °C. Oxidation resistance of hard metals is governed by phase composition, formation mechanism of the scales and protective properties of the oxidation products (CoO, NiO, WO3 and complex oxides, based on the formula (Ni, Co)WO4).
151 citations
01 May 1996-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the authors investigated the high temperature oxidation behavior of WC-Co samples and found that increasing the Co content of the sample led to an improvement in the oxidation behavior, and that at higher flow rates, the oxidation rates decreased with increasing flow rate.
Abstract: The high temperature oxidation behavior of WC-Co samples has been investigated. The oxidation rate of WC-Co was found to increase rapidly with temperature above 600 °C and with the oxygen content of the atmosphere. Increasing the Co content led to an improvement in the oxidation behavior. In all cases, only WO3 and CoWO4 phases were present in the oxide. Although the morphology of the two oxide phases depended on the oxidation conditions, their volume fractions were determined solely by the Co content of the sample. The WO3 formed during the initial stages of oxidation, changed from a strong {{001}} texture at 600 °C to a weak {{200}} texture at 800 °C. As the flow rate of the oxidizing gas was increased, the oxidation rate of WC-Co increased at lower flow rates due to an increase in the oxygen supply to the oxide/sample interface. However, at higher flow rates, the oxidation rates decreased with increasing flow rate.
140 citations
TL;DR: In this paper, the relationship between coating composition, microstructure and mechanical properties was investigated by using X-ray diffraction, Scanning Electron Microscopy (SEM), and Nanoindentation.
109 citations
TL;DR: In this paper, the wear mechanism of TiN-coated carbide and uncoated cermets tools was investigated at various combinations of cutting speed, feed rate, and depth of cut for end milling of hardened AISI H13 tool steel.
101 citations
TL;DR: In this paper, a comprehensive investigation of the wear progress and chip formation was performed on an ultra-fine-grained cemented carbide ball nose end mill coated with a novel nano-multilayered TiAlCrN/NbN coating, by dry machining-hardened steel AISI H13 (HRC 55-57) at a cutting speed of 300m/min.
Abstract: A comprehensive investigation of the wear progress and chip formation was performed on an ultra-fine-grained cemented carbide ball nose end mill coated with a novel nano-multilayered TiAlCrN/NbN coating, by dry machining-hardened steel AISI H13 (HRC 55–57) at a cutting speed of 300 m/min. Flank wear and cutting forces were measured as the wear progressed; chip temperatures were estimated. The surface morphology of the tools were studied by using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis techniques. Results showed that protective oxide films (Al–O, Cr–O and Nb–O) were formed during cutting. With the combination of the protective oxide films and the fine-grain tough substrate, the tool wear rate was greatly reduced compared to the other coatings tested. Continuous and saw-tooth chips were identified, corresponding to a new sharp tool and a worn tool, respectively. The mechanisms of saw-tooth chip formation were found to be a combination of “crack theory” and “adiabatic shear theory”. The characteristics of the chips were studied in detail with the results showing that during formation the chips underwent a combined effect of strain hardening and thermal softening, followed by a quenching phenomenon.
93 citations