Effect of cubic phase composition on gradient zone formation in cemented carbides

Frykholm, Robert; Ekroth, Malin; Jansson, Bo; Andrén, Hans-Olof; Ågren, John

doi:10.1016/s0263-4368(01)00043-9

Cited by 53 publications

(21 citation statements)

References 12 publications

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“…From the X‐ray diffraction (XRD) analysis, only the binder and a solid solution of (Ti,W)C or (Ti,W)(C,N) were found near the surface region. The enrichment in binder phase near the surface region commonly occurs in cemented carbide systems when samples are sintered in a denitriding atmosphere 9,10,17 …”

Section: Resultsmentioning

confidence: 99%

“…Extensive studies 11–18 have been carried out, in an attempt to explain these alternations in surface microstructure. However, discrepancies were found in the interpretations of these phenomena because phase reactions that occur during the sintering process are complex and the formation of solid solutions of carbonitrides in such systems has usually been ignored in these systems.…”

Section: Introductionmentioning

confidence: 99%

“…It is known, however, that the loss of nitrogen from Ti(C,N) during processing causes changes in composition, porosity, 5,6 and sometimes gives rise to an inhomogeneous surface layer in the microstructure. [7][8][9][10] Extensive studies [11][12][13][14][15][16][17][18] have been carried out, in an attempt to explain these alternations in surface microstructure. However, discrepancies were found in the interpretations of these phenomena because phase reactions that occur during the sintering process are complex and the formation of solid solutions of carbonitrides in such systems has usually been ignored in these systems.…”

Section: Introductionmentioning

confidence: 99%

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Change in the Surface Microstructure of Ti(C_0.5N_0.5)–20WC–10Ni–10Co Cermets During Sintering in a Nitrogen Atmosphere

Kim

Kang

2007

Journal of the American Ceramic Society

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Experiments were carried out to determine the effects of introducing nitrogen during sintering on the formation of the surface gradient zone for Ti(C,N)‐based cermets. WC was used as a secondary carbide in a Ti(C,N)–Ni/Co system, and processing was carried out in vacuum, and under various nitrogen conditions (at 1torr). Nitrogen was introduced during various stages of the sintering (above 1300°C). The introduction of nitrogen during the heating stage facilitated the formation of a (Ti,W)(C,N)‐enriched layer to a greater extent than the vacuum conditions. A thermodynamic calculation revealed that denitrification occurs during sintering, even when nitrogen pressure is applied. A nitrogen atmosphere during the heating stage is effective in retarding the dissolution of WC in the cermet matrix. The introduction of nitrogen during the holding or cooling stages also led to an enrichment in the binder phase near the surface. The thickness of the stratified binder layer was strongly related to the cooling rate.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Change in the Surface Microstructure of Ti(C_0.5N_0.5)–20WC–10Ni–10Co Cermets During Sintering in a Nitrogen Atmosphere

Kim

Kang

2007

Journal of the American Ceramic Society

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“…tered at 1450°C for 2 h. It can be clearly observed that there exists a graded layer in the surface zone of the substrate, where its microstructure is apparently different from that in the core zone. In the surface zone, there exists only two types of phases including WC particles and Co-based binder, whereas there are cubic solid solution phases (Ti,W)(C,N) present except for WC and the binder in the core zone, and sometimes black circular or elliptical shape Ti(C,N)(fcc) core may be formed in this zone, which may originate from undissolved cubic phases [14].…”

Section: Methodsmentioning

confidence: 99%

Growth kinetics of cubic carbide free layers in graded cemented carbides

Shi

Liu

Huang

et al. 2012

Int J Miner Metall Mater

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In order to reveal the formation mechanism of cubic carbide free layers (CCFL), graded cemented carbides with CCFL in the surface zone were fabricated by a one-step sintering procedure in vacuum, and the analysis on microstructure and element distribution were performed by scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA), respectively. A new physical model and kinetic equation were established based on experimental results. Being different from previous models, this model suggests that nitrogen diffusion outward is only considered as an induction factor, and the diffusion of titanium through liquid phase plays a dominative role. The driving force of diffusion is expressed as the differential value between nitrogen partial pressure and nitrogen equilibrium pressure essentially. Simulation results by the kinetic equation are in good agreement with experimental values, and the effect of process parameters on the growth kinetics of CCFL can also be explained reasonably by the current model.

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“…In this way, a surface layer forms, depleted of both titanium and nitrogen and enriched in cobalt. In the gradient zone formation process, convective flow and capillary forces' influences are weak enough to be neglected [5].…”

Section: Introductionmentioning

confidence: 99%

Effect of nitrogen introduction methods on the microstructure and properties of gradient cemented carbides

Yang

Xiong

Sun

et al. 2011

Int J Miner Metall Mater

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Gradient cemented carbides with the surface depleted in cubic phases were prepared following normal powder metallurgical procedures. Gradient zone formation and the influence of nitrogen introduction methods on the microstructure and performance of the alloys were investigated. The results show that the simple one-step vacuum sintering technique is doable for producing gradient cemented carbides. Gradient structure formation is attributed to the gradient in nitrogen activity during sintering, but is independent from nitrogen introduced methods. A uniform carbon distribution is found throughout the materials. Moreover, the transverse rupture strength of the cemented carbides can be increased by a gradient layer. Different nitrogen carriers give the alloys distinguishing microstructure and mechanical properties, and a gradient alloy with ultrafine-TiC 0.5 N 0.5 is found optimal.

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Effect of cubic phase composition on gradient zone formation in cemented carbides

Cited by 53 publications

References 12 publications

Change in the Surface Microstructure of Ti(C_0.5N_0.5)–20WC–10Ni–10Co Cermets During Sintering in a Nitrogen Atmosphere

Change in the Surface Microstructure of Ti(C_0.5N_0.5)–20WC–10Ni–10Co Cermets During Sintering in a Nitrogen Atmosphere

Growth kinetics of cubic carbide free layers in graded cemented carbides

Effect of nitrogen introduction methods on the microstructure and properties of gradient cemented carbides

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Effect of cubic phase composition on gradient zone formation in cemented carbides

Cited by 53 publications

References 12 publications

Change in the Surface Microstructure of Ti(C0.5N0.5)–20WC–10Ni–10Co Cermets During Sintering in a Nitrogen Atmosphere

Change in the Surface Microstructure of Ti(C0.5N0.5)–20WC–10Ni–10Co Cermets During Sintering in a Nitrogen Atmosphere

Growth kinetics of cubic carbide free layers in graded cemented carbides

Effect of nitrogen introduction methods on the microstructure and properties of gradient cemented carbides

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Product

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Change in the Surface Microstructure of Ti(C_0.5N_0.5)–20WC–10Ni–10Co Cermets During Sintering in a Nitrogen Atmosphere

Change in the Surface Microstructure of Ti(C_0.5N_0.5)–20WC–10Ni–10Co Cermets During Sintering in a Nitrogen Atmosphere