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1 Journal of Achievements in Materials and Manufacturing Engineering

1 2009

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Structure and properties of the gradient tool materials based on a high-speed steel HS6-5-2 reinforced with WC or VC carbides

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Dobrzański L. A. , Kloc-Ptaszna A.

2009

tom Vol. 37, nr 2

213-237

Purpose: This paper concerns manufacturing and researching a new group of the gradient tool materials, manufactured by a conventional powder metallurgy method, consisting in compacting a powder in a closed die and sintering it. Design/methodology/approach: The materials were obtained by mixing the powders of the HS6-5-2 high-speed steel, tungsten carbide (WC), and vanadium carbide (VC). The mixes were poured one by one into the die, yielding layers with the gradually changing volume ratio of carbides within the high-speed steel matrix. Structural research by using the scanning and transmission electron microscopes, x-ray microanalysis and density, hardness and porosity tests, were performed. Structure and hardness of selected materials after heat treatment were also investigated. Findings: On the basis of the results of the research, it was found that it was possible to obtain gradient materials by the powder metallurgy methods, in order to ensure the required properties and structure of the designed material. It was shown that the new sintered graded materials were characterized by a multiphase structure, consisting of ferrite, primary carbides of the high speed steel, of the MC and M6C type, and dependently of the reinforcement phase, of the tungsten carbide WC or the vanadium carbide VC, which were introduced into the material, in the form of powder. Additionally in the structure of the WC-reinforced materials the W2C phase occurs. The gradient tool materials reinforced with the WC carbide were characterized by a higher hardness, and a lower porosity in relation to the materials reinforced with the VC carbide. It was found that the desired structure and properties (density, porosity and hardness) had the material containing 25% of the WC carbide in the surface layer, after sintering at the temperature 1210oC, for 30 minutes. The heat treatment application causes a significant increase of the surface layer hardness of the material. The highest surface layer hardness, equal to 71.6 HRC, shows the material austenitized at the temperature 1120şC, hardened and tempered twice at the temperature 530oC. Practical implications Developed material is tested for turning tools. Originality/value: The material presented in this paper has layers consisting of the carbide-steel with growing hardness on one hand, and the high-speed steel, characterized by a high ductility on the other.