W części I przedstawiono wyniki badań w zakresie wytwarzania i badania własności infiltrowanych kompozytów stal szybkotnąca-żelazo-miedź. Materiał badawczy stanowiły kształtki ze stali szybkotnącej gatunku M3/2 i stali szybkotnącej z dodatkiem 20 i 50 % proszku żelaza gatunku NC 100.24. 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 min. Następnie porowate kształtki niespiekane i spiekane infiltrowano miedzią, metodą nakładkową w piecu próżniowym w temperaturze 1150 stopni Celsjusza przez 15 min.
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 iron powder were added to the HSS powder prior to compaction. The following compositions were investigated: 100 % M3/2, M3/2 + 20 % Fe and M3/2 + 50 % Fe. 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. Pre-weighed preforms of copper were carefully placed on top of the rigid skeleton 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. Figure 4 shows that the M3/2 grade HSS cannot be fully densified at 1150 degrees of Celsius, and that the as-sintered density is approximately equal to the green density. From Fig 7 it is evident that the as-infiltrated properties of the investigated composites are a complex function of the manufacturing route and tungsten carbide content. The molten copper is drawn into the interconnected pores of the skeleton, through a capillary action, and fills virtually the entire pore volume to yield final densities exceeding 97 % of the theoretical value. The Brinell hardness of the as-infiltrated composites decreases with the increased content of iron powder, whereas the bending strength seems to be not affected by the addition of the iron powder. Considerable differences in hardness between the materials obtained from the two infiltration routes have been observed, with higher hardness numbers achieved with direct infiltration of green compacts.