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Carbon effect in the sintered high-speed steels matrix composites - HSSMC

Matula G.

Journal of Achievements in Materials and Manufacturing Engineering

2012

Vol. 55, nr 1

90--107

Goal: The goal of this monograph is development of the tool materials being the outcome of the concept of merging the surface engineering as the domain of knowledge with technology which is the powder metallurgy. The result are the fabricated materials with the gradient, high-speed steels matrix composites (HSSMC) surface layers on steel substrate, combining the mutually exclusive mechanical properties like the high surface hardness and ductility of a tool. Project/methodology/approach: Modern powder forming technologies were used for fabrication of the developed tool materials, e.g., powder injection moulding, pressureless forming, and classic compacting. Sintering was carried out in the vacuum or protective atmosphere conditions, which makes direct material hardening possible from the sintering temperature. Testing of mechanical properties encompassed hardness testing, bending strength testing, and determining the abrasion wear resistance. Detailed structural examinations were carried out to determine the effect of temperature and atmosphere during sintering on type and size of the carbide- and carbonitride precipitations. Moreover, retained austenite portion was determined after hardening and tempering. Achievements: The original achievement is development of the method of the polymer-powder slurry moulding for fabrication of coatings which, because of the binding agent degradation and sintering, form the homogeneous or gradient HSSMC surface layers on the steel substrate - completed or fabricated in the same technological process. Tool materials fabricated with this method are characteristic of high ductility of the steel core and high hardness of the surface layer. Limitations of research/applications: The assumption of the powder injection moulding technique is forming of the small elements with complex shapes and, therefore, this technology is not designed for fabrication of tools with the big overall dimensions. In case of the pressureless forming of the surface layers from HSSMC on the steel core or in case of regeneration of the tool worn out, the limitations come only from the heating device chamber size and the necessity to heat up the entire treated element. Practical applications: It is anticipated that the worked out and fabricated tool materials of the new generation will fill a gap in respect of the mechanical properties between the relatively ductile high-speed steels and the brittle sintered carbides. The newly developed method may be used in the mass- or piece production conditions making, e.g., regeneration possible of the costly tools’ surfaces. Originality/value: Employment of the modern powders forming techniques, and especially of the pressureless forming and sintering in the flowing nitrogen-hydrogen mixture atmosphere, makes it possible to fabricate tool materials with the layered or gradient structure with the multidirectional growing portion of the hard carbide- or carbonitride phases.

Kształtowanie struktury kompozytów na osnowie stali szybkotnącej infiltrowanych miedzią.

Madej M., Leżański J.

Rudy i Metale Nieżelazne

2001

R. 46, nr 8

380-384

Na strukturę i na własności kompozytów wytwarzanych metodą infiltracji zasadniczy wpływ wywiera charakterystyka kapilar w porowatych kształtkach przeznaczonych do infiltracji. Praca przedstawia wyniki badań dotyczące: kształtowania struktury kapilar w porowatych kształtkach ze stali szybkotnącej pod wpływem dodatków grafitu, miedzi i węglika WC; wpływu morfologii kapilar na przebieg infiltracji oraz na strukturę i własności infiltrowanych miedzią kompozytów na osnowie stali szybkotnącej M3/2.

The structure and properties of composites, generated by infiltration, are principally influenced by the characteristic of capillaries in the porous, shaped, steel elements destinated for infiltration. The paper presents the investigation-results, refering to formation of the structure of capillaries in porous, high-speed steel shape-elements, under the influence of graphite, copper and carbide, WC, additions, and influence of capillaries-morphology on the run of infiltration and on the structure of copper-infiltrated composites with high-speed steel M3/2 matrix.