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2 Journal of Achievements in Materials and Manufacturing Engineering

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Effect of WC concentration on structure and properties of the gradient tool materials

Dobrzański L. A., Kloc-Ptaszna A., Dybowska A., Matula G., Gordo E., Torralba J. M.

Journal of Achievements in Materials and Manufacturing Engineering

2007

Vol. 20, nr 1-2

91-94

Purpose: The goal of this work is to obtain the contemporary gradient materials based on the tungsten carbide reinforced high-speed steel using the conventional powder metallurgy method and increasing the high-steel hardness (80 HRA = 800 HV) by introducing the tungsten carbide as the reinforcing phase, with hardness exceeding 2200 HV. Design/methodology/approach: The materials were fabricated with the conventional powder metallurgy method consisting in compacting the powder in the closed die and finally sintering it. Forming methods were developed for powders of the HS6-5-2 high speed steel and WC, making it possible to obtain material with seven layers in the structure. Findings: It was found out basing on the microhardness tests that hardness of test pieces grows along with the sintering temperature and with WC content in the interface layers and in the high-speed steel ones. It was also observed that porosity decreases along with the WC concentration increase in these layers. It was found out, basing on the comparison of structures and properties of the compacted and sintered test pieces, that in structures of all examined test pieces in the sintered state fine carbides occurred distributed homogeneously in the high-speed steel layer. Research limitations/implications: It was noticed, that increase of the sintering temperature results in the uncontrolled growth and coagulation of the primary carbides and melting up to forming of eutectics in layers consisting of the high-speed steel. Practical implications: Material presented in this paper has layers consisting on one side from the mix of the high-speed steel and WC, and on the other side the high-speed steel, characteristic of the high ductility. Such material is tested for milling cutters. Originality/value: The layers were poured in such way that the surface layer consists of the mix of the high-speed steel and WC, and the middle one from the high-speed steel. The layers inside the material are mixes of the high-speed steel and WC in the relevant proportions.

Influence of the chemical composition and particle size of the metal matrix, on TiCN-reinforced Fe-based composites

Gómez B., Gordo E., Ruiz-Navas E. M., Torralba J. M.

Journal of Achievements in Materials and Manufacturing Engineering

2006

Vol. 17, nr 1-2

57-60

Purpose: The objective of this work is to study the influence of different parameters as the chemical composition and particle size of the metal matrix, on TiCN-reinforced Fe-based composites. Design/methodology/approach: In order to obtain the composite powder two different types of blending were used, conventional blending and high energy milling (HEM). The HEM was carried out in a planetary ball mill during 12 hours, with a rotating speed of 400 rpm, and a ratio ball:powder of 10:1 (in mass). The atmosphere was Argon to prevent the oxidation. After the preparation of powders, compacts were produced by uniaxial pressing at 700 MPa and sintering under vacuum. The sintering temperatures varied between 1350oC and 1450oC, for 60 min. Sintered samples were characterised by determination of density, dimensional change, Vickers hardness (HV30), bending strength, and C, N contents (by LECO). The microstructural study was carried out by scanning electron microscopy (SEM). Findings: As a result of the study it is clear that the presence of carbides in the metal matrix allows the increasing of mechanical properties of sintered composites, and these properties are related with the microstructure and C/N ratio. Practical implications: In this research 50 % vol of hard phase is introduced, following a simpler and lowercost route, as pressing and sintering. It is true that high-energy milling raises the cost of the processing. This is why conventional blending of small size powder particle has also been done in this work. The latter route has shown to give quite promising results, reaching hardness values about 2000 HV30. Originality/value: In this work, composite materials with high hardness have been obtained following a simple and low-cost route.