Własności i mikrostruktura infiltrowanych kompozytów stal szybkotnąca-miedź, Część 2

• Autorzy: Madej M.

Warianty tytułu

EN

The properties and structure of infiltrated high speed steel-copper composites, Part 2

• Języki publikacji: PL

Abstrakty

PL

W części II przedstawiono wyniki badań w zakresie wytwarzania i badania mikrostruktury infiltrowanych kompozytów stal szybkotnąca-żelazo-miedź. Materiał badawczy stanowiły kształtki ze stali szybkotnącej gatunku M3/2 i stali szybkotnącej z dodatkiem 7,5 % elementarnego proszku miedzi oraz stali szybkotnącej z dodatkiem 0,3 % grafitu. Porowate kształtki przeznaczone do infiltracji prasowano pod ciśnieniem 800 MPa, część z nich poddano spiekaniu w piecu próżniowym w temperaturze 1150 stopni Celsjusza przez 60 minut. Następnie porowate kształtki niespiekane i spiekane infiltrowano miedzią, metodą nakładkową w piecu próżniowym w temperaturze 1150 stopni Celsjusza przez 15 minut.

EN

High hardness, mechanical strength, heat resistance and wear resistance of M3/2 grade high speed steel (HSS) make it an attractive material for manufacture of valve train components. In this application, the material must exhibit resistance to oxidation, high hot strength and hardness, and superior wear resistance. Metal matrix composites are usually produced by the infiltration technique. Infiltration is a process that has been practiced for many years. It is defined as a process of filling the pores of a sintered or unsintered compact with a metal or alloy of a lower melting point. In the particular case of copper infiltrated iron and steel compacts, the base iron matrix, or skeleton, is heated in contact with the copper alloy to a temperature exceeding the melting point of the copper, normally to between 1095 and 1150 degrees of Celsius. Since technological and economical considerations are equally important, infiltration of high-speed steel based skeleton with liquid cooper has proved to be a suitable technique whereby fully dense material is produced at low cost. The aim of the present study was to produce high speed steel-iron-copper composites, which should have acceptable density, wear resistance and good sliding prosperities. Various amounts of copper and graphite powders were added to the HSS powder prior to compaction. The following compositions were investigated: 100 % M3/2, M3/2 + 7.5 % Cu and M3/2 + 0.3 %C. The mixtures were prepared by mixing for 30 minutes in the 3-D pendulum motion Turbula/R T2C mixer. Then the powders were cold pressed in a rigid cylindrical die at 800 MPa. Both green compacts and pre-sintered compacts (pre-sintering condition: 1150 degrees of Celsius in vacuum for 60 minutes) were infiltrated with copper. The infiltration process was carried out in vacuum better than 10-3 Pa. Preweighed preforms of copper were carefully placed on top of the rigid skeletons in which porosity were predetermined, heated up to 1150 degrees of Celsius, subsequently held at temperature for 15 minutes, and cooled down with the furnace to the room temperature. The dilatometer was used to detect some reaction in the sintering. The changes in as pressed and as sintered density, hardness, bending strength and tribological properties are discussed in this work. The near fully-dense material made of M3/2 grade powder can be achieved by sintering at temperature 1250 degrees of Celsius [3, 5]. Because the main goal of this attempts was to produce the porous skeleton, the lower sintering temperature was applied. From the microstructural observations (Fig. 3 and 4) it may be concluded that the morphologies of capillaries are mainly affected by the manufacturing route and powder characteristics. It can be seen that the microstructure of the M3/2 grade HSS based composites consists of a steel matrix with finely dispersed carbides and islands of copper. Figures 6 and 11 shows tungsten carbides located within the grains and on the grain boundaries as well. The qualitative EDX analysis revealed the presence of both MC type vanadium-rich carbides and M6C type tungsten and iron rich carbides. From the microstructural observations and obtained results it may be concluded that the infiltration with copper almost completely eliminates porosity.

Słowa kluczowe

PL

stal szybkotnąca; miedź; grafit; prasowanie; spiekanie; infiltracja; kompozyty; mikrostruktura

EN

high-speed steel; copper; graphite; pressing; sintering; infiltration; composites; properties; microstructure

• Wydawca: Wydawnictwo SIGMA-NOT
• Czasopismo: Rudy i Metale Nieżelazne
• Rocznik: 2010
• Tom: R. 55, nr 11
• Strony: 805--810
• Opis fizyczny: Bibliogr. 8 poz., rys., wykr.

Twórcy

autor

Madej M.

• Akademia Górniczo-Hutnicza, Wydział Inżynierii Metali i Informatyki Przemysłowej, Kraków

Bibliografia

• 1. Leżański J.: Kinetyka infiltracji cieczy w porowatych materiałach z proszków. Archiwum Hutnictwa 1989, nr 1, s. 93-108.
• 2. Greetham G.: Mechanically locked sintered valve seat inserts. Metal Powder Report, t. 44, nr 2, s. 34.
• 3. Greetham G.: Development and performance of infiltrated and non-infiltrated valve seat insert materials and their performance. Powder Metallurgy, 1990, t. 33, nr 3, s. 112-124.
• 4. Palma R. H.: Tempering response of copper alloy infiltrated T15 high speed steel. The International Journal of Powder Metallurgy, 2001, t. 37, nr 5, s. 29-35.
• 5. Igharo M., Wood J. V.: Effect on consolidation parameters on properties of sintered high speed steels. Powder Metallurgy, 1990, t. 33, nr 1, s 70-76.
• 6. Greetham G.: High density high speed steels, PM into the 1990’s, International Conference on Powder Metallurgy. London, 2-6 July 1990, t. 2, s. 206-216.
• 7. Bolton J. D., Gant A. J.: Phase reactions and chemical stability of ceramic carbide and solid lubricant particulate additions within sintered high speed steel matrix. Powder Metallurgy, 1993, t. 36, nr 4. s. 267-274.
• 8. Leżański J., Rutkowski W.: Kinetics in Porous Iron Infiltration Using Cu-Fe Alloy. Planseeberichte fur Pulvermetallurgie, 1975, t. 23, nr 3, s. 195-208.