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Four types of silicon carbide/carbon nanotubes composites were prepared with the main aim to develop ceramics with enhanced electrical conductivity. The SiC/CNT composites were prepared by in-situ growth of CNT on the SiC powder grains. Three types of SiC/CNT composites, where the precursor SiC/CNT powder mixture was prepared by Catalytic Chemical Vapour Deposition (CCVD) method and different amounts of Fe catalytic nanoparticles (2.5, 5, 10 wt% Fe), were designed. In addition, one reference material containing 2.5 wt% Fe catalytic nanoparticles but without CCVD application, i.e. without CNT, was prepared in order to correctly assess the role of CNT. The experimental materials were compacted by hot pressing (1850 °C/Ar/60 min/40 MPa). Mechanical properties such as hardness and elastic modulus of experimental materials were determined. Electrical conductivity as a function of CNT content was measured. The effect of the CNT addition on tribological properties (coefficient of friction, wear) of SiC/CNT composites was also observed. Hardness of the reference sample was relatively high (HV1 = 24 GPa) and it decreased down to HV1 = 17–19.8 GPa with presence of CNT. Similarly, the fracture toughness decreased with presence of CNT from 4.99 MPa.m1/2 for the reference sample down to 3.4–4 MPa.m1/2 for the SiC/CNT composites. Nanoindentation showed that hardness HIT of reference sample without CNT was around 26 GPa and with increasing amounts of CNT it decreased down to 21 GPa. The composites had similar modulus of elasticity (EIT = 337–348 GPa), while for the reference sample it was EIT = 434 GPa. Electrical conductivity increased with amount of CNT (1.76 S/m for the reference sample, 484.3 S/m for the composite with 2.5 wt% Fe, and up to 2873.6 S/m for the composite with 10 wt% Fe). Specific wear rate increased with presence of CNT from 7.7 × 10−7 mm3/Nm for the reference sample to 2.4–2.9 × 10−6 mm3/Nm for the composites. Complex wear behavior common for all types of experimental materials was observed: mainly abrasion, mechanical wear (micro-fractures) and tribochemical reactions with created SiO2 layer. In the reference sample the dominant wear mechanism was abrasion, in SiC/CNT composites formation of transferred films in wear tracks consisting of oxides and carbon phases formed by crushing the CNT were observed.

Three different types of SiC based cermets with various content (30, 40, 50 wt.%) of electrically conductive TiNbC phase have been fabricated by hot-pressing without sintering additives. The effect of TiNbC content on the basic mechanical, electrical and tribological properties of SiC-TiNbC cermets was investigated. Tribological properties have been characterized by the ball-on-disc method at the ambient temperature and dry wear conditions with air humidity 35–40% at the load of 5–30 N, sliding distance of 500 m, with the static partner made from SiC. Corresponding wear rate was calculated and wear mechanisms were identified. Resulting materials were relatively hard, with increasing amount of TiNbC the hardness increased from 19.8 ± 1 GPa for 30 wt.% of TiNbC up to 25.4 ± 0.9 GPa at 50 wt.% of TiNbC. The fracture toughness values were independent on TiNbC phase and varied between 2.7 and 2.9 MPa.m 1/2 . Similarly, Young's modulus increased from 354 GPa to 435 GPa. It was found that electrical conductivity of SiC cermets was rapidly improved with increased fraction of metallic phases and was three orders of magnitude higher at 30 wt.% TiNbC addition and around four order of magnitude higher at 50 wt.% of TiNbC metallic phase comparing to conventional semiconductive SiC ceramics with electrical conductivity ~ 10 Sm − 1 . Coefficient of friction (between 0.3 and 0.5) and wear resistance (10 − 6 –10 − 7 mm 3 /Nm) were comparable with the wear resistant SiC materials.

In this work, the WC-Co carbide/1020 steel brazed joints which were prepared by Tungsten Inert Gas (TIG) process using different brazing currents have been studied. The peak temperature reached by increasing the brazing current caused remarkable inter-diffusion of Ni, Mn, Cu and Co elements between the braze and the base materials. The higher the brazing current was, the larger the diffusion extent of these elements became and the greater the WC rearrangement occured. As the diffusion rate of Ni towards the WC-Co was enhanced through increasing brazing current, a short range diffusion of Co element towards the braze was recorded. A Special Shear Test (SST) conducted at room temperature revealed the best bonding strength for the current of 80A. Besides, hardness (HIT) and elastic modulus (EIT) values of the interfaces were situated between those of the braze and the base materials.