**Author details**

Iwona Sulima\*

**4. Conclusions**

148 Sintering Techniques of Materials

Composite materials based on austenitic stainless steel with varying concentration of TiB2 ceramics were fabricated. Four variants of the composites were obtained applying the technique of powder metallurgy and the two modern sintering processes, i.e. High Pressure-High Temperature (HP-HT) process and Spark Plasma Sintering (SPS). Based on the results obtained, it has been proved that the introduction of TiB2 ceramics to the austenitic steel matrix is an efficient way to improve the composite properties. With increasing volume fraction of the reinforcing phase, an improvement in the physical, mechanical and tribological properties was observed. The best composite properties were obtained for the TiB2 content of 8 vol%.

The study also showed a significant effect of the applied method of sintering on the properties of the tested materials. In all the composites sintered by HP-HT (at 1000°C and 1300°C, 5 GPa) and by SPS (only at 1100°C, 5 min), a very high degree of consolidation was obtained. It was the result of the combined effect of heat and high pressure in the case of the HP-HT method and of the use of electric discharges, high-rate heating and properly selected temperature in the case of the SPS process. Comparing the effect of the sintering methods used it can be concluded that the HP-HT process is a promising method for sintering the TiB2-reinforced composites. Generally, the materials sintered at temperature of 1300°C and pressure of 5GPa were characterised by optimal microhardness and very good mechanical, plastic and tribo‐ logical properties. In contrast, the use of SPS reduced the sintering temperature of composites, because already at a temperature of 1100°C and the duration of 5 min sinters with satisfactory density were produced. The best combination of physico-mechanical and tribological prop‐ erties was obtained in the composites sintered at 1100°C. Careful analysis of the results has showed that the temperature of 1000°C was too low to produce a composite material with high

The sintering process carried out by either HP-HT or SPS has yielded the composite materials of a uniform and consistent structure produced within the whole volume of the sintered product. A homogeneous distribution of the reinforcing TiB2 phase was obtained in the matrix of all the sintered products. The reinforcing phase showed a tendency to settle along the matrix grain boundaries. It has been demonstrated that the applied method of sintering and sintering conditions have a significant impact on changes in the microstructure of the tested composites. Application of the SPS process promotes the formation of new phases at the matrix boundary.

The author would like to thank Prof. Lucyna Jaworska and Paweł Figiel, Ph.D. and Piotr Putyra, Ph.D. from Institute of Advanced Manufacturing Technology in Cracow for help in

degree of consolidation and satisfactory properties.

**Acknowledgements**

SPS process of composites.

Address all correspondence to: isulima@up.krakow.pl

Institute of Technology, Pedagogical University of Cracow, Krakow, Poland
