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The effect of zirconium diboride (ZrB2) and titanium diboride (TiB2) on the microstructure as well as the physical, mechanical, and tribological properties of composites based on 316 L steel is presented. Each reinforcing phase was added to the base alloy in the amount of 5 wt% and 10 wt%. The composites were fabricated by the SPS process (Spark Plasma Sintering). The results show that the weight fraction of the reinforcing phase affects the physical, mechanical, and tribological properties of the sintered composites. The sintered materials were characterized by a very high level of density. The addition of TiB2 has proved to be effective in increasing the hardness and compressive strength of the composites. The hardness of the composites with the addition of 10% TiB2 increased by 100% compared to the hardness of sintered 316L steel. It was found that introducing ZrB2 to the steel matrix significantly improved the wear resistance of the composites. The results showed that compared to 316L steel with the wear rate of 519 × 10−6 mm3/Nm, the wear rate of the composites containing 10% ZrB2 decreased more than twice, i.e., to 243 × 10−6 mm3/Nm. [ABSTRACT FROM AUTHOR]

This paper presents the technology of powder sintering by the spark plasma sintering method, also known as the field assisted sintering technique. The mechanisms, compared to other sintering techniques, advantages of this system, applied modifications and the history of the development of this technique are presented. Spark Plasma Sintering (SPS) uses uniaxial pressing and pulses of electric current. The direct flow of current through the sintered material allows high heating rates to be reached. This has a positive effect on material compaction and prevents the grain growth of sintered compact. The SPS mechanism is based on high-energy spark discharges. A low-voltage current pulse increases the kinetics of diffusion processes. The SPS temperature is up to 500 °C lower than the sintering temperature using conventional methods. The phenomena that occur during sintering with the Field Assisted Sintering Technology (FAST)/SPS method give great results for consolidating all types of materials, including those which are nonconductive. This method is used, among others, in relation to metals, alloys and ceramics, including advanced and ultra-high-temperature ceramics. Due to the good results and universality of this method, in recent years it has been developed and often used in research institutions, but also in industry. [ABSTRACT FROM AUTHOR]

In this work, Fe-Mn-Cu-Sn-C alloys were prepared by means of powder metallurgy (PM). Powder mixtures were ball-milled for 8, 30 and 120 h and densified to < 1% porosity using spark plasma sintering (SPS) at 900 °C and 35 MPa. After consolidation, all samples of the Fe alloys were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), hardness and flexural strength tests. Resistance to abrasive wear was evaluated in both three-body abrasion and two-body abrasion tests. The SEM observations revealed an evident dependence of grain size and microstructural homogeneity on milling time. The XRD analysis showed a marked increase in austenite content in the as-sintered specimens with milling time. Although the proportion of deformation-induced martensite was small, the strengthening effect of abrasion on the subsurface layer of the investigated alloys was clearly indicated by Knoop hardness measurements. [ABSTRACT FROM AUTHOR]

Titanium diboride (TiB2) is a hard, refractory material, attractive for a number of applications, including wear-resistant machine parts and tools, but it is difficult to densify. The spark plasma sintering (SPS) method allows producing TiB2-based composites of high density with different sintering aids, among them titanium silicides. In this paper, Ti5Si3 is used as a sintering aid for the sintering of TiB2/10 wt % Ti5Si3 and TiB2/20 wt % Ti5Si3 composites at 1600 °C and 1700 °C for 10 min. The phase composition of the initial powders and produced composites was analyzed by the X-ray diffraction method using CuKα radiation. The microstructure was examined using scanning electron microscopy, accompanied by energy-dispersive spectroscopy (EDS). The hardness was determined using a diamond indenter of Vickers geometry loaded at 9.81 N. Friction–wear properties were tested in the dry sliding test in a ball-on-disc configuration, using WC as a counterpart material. The major phases present in the TiB2/Ti5Si3 composites were TiB2 and Ti5Si3. Traces of TiC were also identified. The hardness of the TiB2/Ti5Si3 composites was in the range of 1860–2056 HV1 and decreased with Ti5Si3 content, as well as the specific wear rate Wv. The coefficient of friction for the composites was in the range of 0.5–0.54, almost the same as for TiB2 sinters. The main mechanism of wear was abrasive. [ABSTRACT FROM AUTHOR]

The aim of this study was to carry out the consolidation of zirconium diboride-reinforced composites using the SPS technique. The effect of the adopted method of powder mixture preparation (mixing in Turbula or milling in a planetary mill) and of the reinforcing phase content and sintering temperature on the microstructure, physical properties, strength and tribological properties of sintered composites was investigated. Experimental data showed that the maximum relative density of 94–98% was obtained for the composites sintered at 1100 °C. Milling in a planetary mill was found to contribute to the homogeneous dispersion and reduced clustering of ZrB2 particles in the steel matrix, improving in this way the properties of sintered steel + ZrB2 composites. Morphological and microstructural changes caused by the milling process in a planetary mill increase the value of Young's modulus and improve the hardness, strength and wear resistance of steel + ZrB2 composites. Higher content of ZrB2 in the steel matrix is also responsible for the improvement in Young's modulus, hardness and abrasive wear resistance. [ABSTRACT FROM AUTHOR]

This work deals with the preparation of composites from the ZrB 2 -HfB 2 -MeX system (where: MeX = SiC, B 4 C, WC, MoSi 2 and CrSi 2). Three pressure-assisted sintering techniques were used to obtain the composites, i.e. hot-pressing (HP), spark-plasma sintering (SPS) and high pressure-high temperature (HPHT) sintering. Hot-pressing was selected as the most favourable sintering technique. The composites obtained via hot-pressing were characterized by high density and homogeneous microstructure. The work did not undermine or justify the need to reduce passivating oxide layers on boride grains. In the case of silicides, especially chromium silicide, there was a significant reduction in the sintering temperature of the ZrB 2 -HfB 2 composites by about 500–600°C. In composites with the addition of silicides, there is a tendency to create complex solid solutions, which is visible as core-shell microstructures. [ABSTRACT FROM AUTHOR]

The sintering behaviours, phase compositions, microstructures, and mechanical properties of Al 2 O 3 -based matrix composites reinforced with up to 20 vol% of cubic boron nitride (cBN, super-hard phase) were investigated. The materials were prepared via the method of spark plasma sintering (SPS). Additionally, pure cBN powder was treated under identical SPS conditions for the purpose of comparison. The temperatures at which hexagonal boron nitride (hBN, graphite-like phase) was detected in pure cBN and in cBN dispersed in the Al 2 O 3 + 10 TiN matrix were 1600 °C and 1300 °C, respectively. The presence of additives in the Al 2 O 3 matrix had a pronounced influence on the formation of hBN, with TiN > ZrO 2 > pure Al 2 O 3. All the composites exhibited quite good improvements in fracture toughness, of about 1.5 MPa·m1/2 on average over that of Al 2 O 3. Crack deflection on cBN grains was identified as the main toughening mechanism of the ceramics investigated. Unlabelled Image • Composites containing cubic boron nitride (cBN) have been sintered at low pressure. • Spark plasma sintering (SPS) method allows to obtain full dense composite at 1300 °C. • Al 2 O 3 -based composites with cBN have better fracture toughness than pure Al 2 O 3. • During SPS pure cBN is more stable then cBN dispersed in ceramic matrix. • TiN promotes of graphite-like, hexagonal boron nitride formation most extensively. [ABSTRACT FROM AUTHOR]