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Improved manufacturing of hard metals and sintered steels via tailored carbon source

In both sintered steels and hard metal industries carbon plays a unique role as reducing and carburizing agent. This project is aimed to cover the common lack of knowledge: the effect of the type of carbon source on the combined interaction between material, carbon and processing atmosphere.

Carbon is the basic alloying element in structural steels and hard metal parts produced by Powder Metallurgy (PM) manufacturing processes. However, the full potential of exploiting the variety of carbon sources nowadays available in the market, and the impact that this can have on the final products has not yet been industrially realized. The project proposed here originates from a common interest between Hard Metals and Sintered Steels producers, in Switzerland and Sweden, for the development of more efficient PM-manufacturing processes to take advantage of the selection and usage of different carbon sources. The aim of the project is to develop knowledge about the interaction of solid carbon sources, atmosphere and solid metal/oxides to improve the efficiency of PM-manufacturing processes. This will then be applied by the SMEs involved in the project for the production of both sintered steels and hardmetals. The possibility to apply this knowledge in two different PM industries enhancing the opportunities of commercialization. The innovation of this project lies in harnessing the carbon structure to improve the production of either cemented carbides or sintered steels. These two cases have been selected because, among all of the industries based on powder processing, particularly cemented carbides and sintered steels require the most accurate carbon control during sintering and therefore, the process must be precisely designed to obtain the desired carbon level in the final product. The reactivity of the carbon source with the material plays a major role in the process, but also the reactivity of the carbon source with the atmosphere, and the effect of this interaction on the materials being processed needs to be considered. For instance, the strong interaction between solid carbon and processing atmosphere will affect the composition of the atmosphere and also the amount of carbon available to react with the processed material. In sintered steels, atmosphere quality and carbon control are crucial for improving strength and toughness, but most importantly, for maintaining consistent sintering output quality. In cemented carbides, carbon control is the key to attain the desired hardness, strength, wear resistance and fracture toughness. If the carbon stoichiometry is not preserved during sintering exaggerating grain growth occurs, and embrittling phases can be formed. A systematic study will be carried out combining different atmosphere compositions and different carbon sources in order to understand their effects on the properties and on the effective interaction with the processed material. The investigation will be based on: - Thermodynamic and kinetic studies of reactions between carbon-gaseous atmosphere-solid metal/oxide. - Analyses of sintering/synthesis processes using advanced thermal analysis techniques. - Microstructural characterization and surface analyses to determine the extent and relevance of surface interactions. On a first stage, similar studies on different materials will provide basic knowledge about the reactivity of different carbon sources (natural and primary synthetic graphites with different crystallinities, carbon black, etc.) in different atmospheres. This common knowledge will afterwards be applied by the SMEs involved to optimize the specific processes used in sintered steels or hard metals production. Novel nano-sized WC powders for improved properties of the final hard metal components and combination of lean sintering atmosphere with tailored carbon sourcess will bring significant cost and performance benefits for the SMEs involved in this project.
Acronym: 
CarbonHM&PM
Project ID: 
9 156
Start date: 
01-09-2014
Project Duration: 
18months
Project costs: 
140 000.00€
Technological Area: 
Moulding, injection moulding, extrusion, sintering
Market Area: 
Chemicals and Materials

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