Marcin Madej

Microstructure and Tribological Properties of a Material with Cementite Eutectic Applied for Metallurgical Rolls

Three prototype metallurgical rolls were produced on the basis of G200CrNiMo4-3-3 material. The method applied for the microstructure forming was different for each roll: the roll marked WOT – as cast state (without a modification and heat treatment); the metallurgical roll marked WMT – during its casting the FeCaSi deoxidizing was applied and then modification by a complex inoculant and argoning; the metallurgical roll marked WNT – subjected to a heat treatment (incomplete normalizing).The mentioned above differences in the technology of making rolls caused changes in their microstructure.The cementite eutectic and pearlitic matrix occurred in each roll. The main differences in the microstructure of cast steel rolls concerned a morphology of precipitates of hypereutectoid cementite. In the WOT roll cementite was mainly in the Widmannstӓtten system. Precipitates of hypereutectoid cementite in the WMT roll occurred along grain boundaries of primary austenite. A large fraction of spheroidal hypereutectoid cementite, precipitated in the whole volume of the primary austenite grain, appeared in the WNT roll. The microstructure influenced the rolls hardness and was equal 260 ÷ 350 HBW.Tribological investigations indicated decreasing the abrasive wear resistance with increasing the hypereutectoid cementite fraction within the primary austenite grains.

The Influence of Microstructure of Medium Carbon Heat-Treatable Steel on its Tribological Properties

The hereby work presents the influence of microstructure on the tribological properties of medium carbon heat-treatable steel. These steel is used for various elements of which in addition to high wear resistance a high plasticity is required. For tested steel there different heat treatments were performed in order to obtain the different microstructure and properties. Each sample was hardened from the same temperature, which has been selected on the basis of standards for these steel and it was equal 890 °C. Two samples were quenched after austenitising in water. After quenching one of the samples was cooled in liquid nitrogen for 30 minutes (sub-zero treatment). After that these two samples were tempered in the preheated furnace at 200 °C for 2 hours. The third sample immediately after austenitising was quenched in mixture of molten salts heated to 200 °C (fused salt quenching). After these three carried out heat treatments the various microstructures were obtained with preserved high hardness. After heat treatment samples for the tribological test were prepared. The test was performed using the T-05 type roll-block test machine. This type of test machine is used to obtain the resistance to friction wear of metals and others. Thanks to these tribological tests and mass loss measurements the best heat treatment, which significantly increase of the wear resistance for tested steels was indicated.

Infiltration as a Method of Fabrication of HSS Based Composites

Attempts have been made to describe the influence of copper infiltration on properties of HSS based composites with different iron additions. Iron powder were used to reduce price of composites. The powder compositions used to produce skeletons for further infiltration were M3/2, M3/2 + 7,5%Cu, M3/2+20%Fe and M3/2+50%Fe. The powders were cold pressed at 800 MPa. These as-pressed specimens were used for direct copper infiltration.

The Properties and Structure of Infiltrated High Speed Steel-Tungsten Carbide - Copper Composites

The aim of the present study was to produce high speed steel – tungsten carbide – copper composites, which should have acceptable density, wear resistance and good sliding prosperities. Various amounts of WC powder were added to the HSS powder prior to compaction. The following compositions were investigated: 100% M3/2, M3/2 + 10% WC and M3/2 + 30%WC. The mixtures were prepared by mixing for 30 minutes in the 3-D pendulum motion Turbula® 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°C in vacuum for 60 minutes) were infiltrated with copper. The whole 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 skeletons in which porosity were predetermined, heated up to 1150°C, 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 Influence of Production Process Parameters on the Properties W-Ag, Mo-Ag Composites

Attempts have been made to describe the influence of production process parameters on the microstructure and properties of W - Ag and Mo - Ag composites. The compositions of powder mixtures are W + 30% Ag and Mo + 30%Ag. Silver additions assists densification during sintering by a liquid phase sintering process. The main goal of this work is to compare properties and microstructure of as-sintered and as-infiltrated composites.