R. Dziurka

The Analysis of the First Stage Tempering of the Medium Carbon Cr-Mn-Mo Alloy Steel

The work includes the studies of the first stage tempering of the medium carbon Cr-Mn-Mo alloy steel, and occurredprecipitations of carbides. Dilatometric analysis allowed to trace precisely the changes that occur during the first stage of tempering and associate them with the various phase transformations. With the use of the high resolution scanning electron microscope it was able to photograph very small precipitation occurred in the investigated steel after low tempering. Analysis of these images allowed to determined the crystallographic plane in which the precipitation increases, and angles between these planes. With these obtained information it was able to identifiedthe precipitations, as a cementite carbides.

The Role of Microstructure in High Temperature Tribology of Iron Alloys

The present paper describe the issue of tool materials wear in a high temperature conditions. The investigations were performed at the cast steel tool material at the tribological contact to the structural steel. The investigations aim was to determine the role of microstructure in a tribological properties between the structural steel and tool material. The results of such investigation could be referenced to the industry conditions and could answer about the problems of tool materials wear. The observations of the wear mechanisms were referred to the microstructure of the mill rolls. The laboratory tests ware aimed at evaluating the thermal treatment modification effect on the cast steels properties. A significant role of the morphology of ledeburitic cementite and secondary cementite on the tribological properties was exhibited. The investigations assumed the presence of an austenitic matrix with primary and secondary cementite. Influence of varying morphology carbides was described. in the cast steel microstructure. The investigation results make possible to point to a direction of carbide morphology change with the purpose of obtaining the assumed properties of hot operation tools.

Analysis of Phase Transformations of Supercooled Austenite in Low-Alloy Steel with Boron Additives

Adiagram of transformations in low-alloy boron-containing steel B27 with high resistance to abrasive wear is plotted under continuous cooling. Chemical, metallographic and dilatometric analyses are performed, and the hardness of the steel is measured. Continuous cooling curves are obtained from the temperature of austenitization at a rate of 0.17 – 25 K/sec in the temperature range of 800 – 500°C.

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.