The paper presents the results of the mechanical, electrical, CCSEM and XRD measurements of hard coal, conducted in simulated conditions of sintering in atmospheres of O2/CO2,. The changes of the coal ash resistivity are correlated with the content of the oxides and with the sintering temperature determined by the mechanical test and Leitz method. The SEM-EDS analysis was conducted for deposits on the probe. The changes of the measured ash samples, observed during sintering process in O2/CO2 atmosphere, were discussed in the ash microstructure point of view.

Using the available analytical methods, including the determination of chemical composition using wavelength-dispersive X-ray

fluorescent spectroscopy technique and phase composition determined using X-ray diffraction, microstructural observations in a highresolution

scanning microscope equipped with an X-ray microanalysis system as well as determination of characteristic softening and

sintering temperatures using high-temperature microscope, the properties of particular chromite sands were defined. For the study has been

typed reference sand with chemical properties, physical and thermal, treated as standard, and the sands of the regeneration process and the

grinding process. Using these kinds of sand in foundries resulted in the occurrence of the phenomenon of the molding mass sintering.

Impurities were identified and causes of sintering of a moulding sand based on chromite sand were characterized. Next, research methods

enabling a quick evaluation of chromite sand suitability for use in the preparation of moulding sands were selected.

The results of structure and mechanical properties investigations of tungsten heavy alloy (THA) after cyclic sintering are presented. The

material for study was prepared using liquid phase sintering of mixed and compacted powders in hydrogen atmosphere. The specimens in

shape of rods were subjected to different number of sintering cycles according to the heating schemes given in the main part of the paper

From the specimens the samples for mechanical testing and structure investigations were prepared. It follows from the results of the

mechanical studies, that increasing of sintering cycles lead to decrease of tensile strength and elongation of THA with either small or no

influence on yield strength. In opposite to that, the microstructure observations showed that the size of tungsten grain increases with

number of sintering cycles. Moreover, scanning electron microscope (SEM) observations revealed distinctly more trans-granular cleavage

mode of fracture in specimens subjected to large number of sintering cycles compared with that after one or two cycles only.

Currently is the biggest problem of metallurgical companies the increase of fossil fuel prices and strict environmental regulations. As a result of this, companies must look for alternatives that would reduce the amount of fossil fuels and reduce emissions. Wood sawdust has huge energy potential, which can be used in the process of agglomerate production. This type of energy is locally available, has some similar properties as fossil fuels and is economically advantageous. For these reasons, experimental study using laboratory agglomeration pan was realized to study the possibility of agglomerate production with a mixed fuel. Experimental results show the viability of mixed fuel use in the agglomeration process, but also show significant possibility for improvement. The maximum acceptable substitution ratio, which corresponds to qualitatively suitable agglomerate is 20% of pine sawdust. Based on the realized experiments and the obtained results we have acceded to the intensification of the agglomeration process with an objective to increase the amount of added substitution fuel while maintaining the required quality of agglomerate.

In this paper the development and method of production of modern, Ni-free sintered structural steels containing Cr, Mn and Mo, enabling the production of structural sintered steels in industrial conditions, using safe, with low H2-content, sintering atmospheres is presented. For this purpose, the analysis of microstructure and mechanical properties of these sintered structural steels produced in different processing conditions and also the connections between the microstructure of sintered material and its mechanical properties, was presented. Following the investigations, the appropriate chemical composition of sintered Ni-free steels with properties which are comparable or even better than those of sintered structural steels containing rich and carcinogenic nickel was choosen. Additionally, in the paper the properties of electrolitically coated carbon steels were presented, as the beginning of investigation for improving the mechanical properties of alloyed, structural sintered steels.

This work presents the development of a safer processing route for hard metals. Traditional processing of fine particles under organic solvents presents significant explosion risks. The milling under dichloromethane (DCM) reduces the risks associated with fire hazards. After milling and drying, the samples have been sintered in an industrial sintering furnace under a vacuum at 1380°C. The materials’ characterisation has been done by X-ray diffraction, scanning electron microscopy, particle size analysis, optical microscopy, and by magnetic measurements. The present work results reveal the powders’ appropriate properties after milling and drying and the desired biphasic (Co-WC) phases obtained after sintering, thus proving the feasibility of such a route, therefore the diminishing of specific fire hazards.

The effect of the compaction rate on the structure, microstructure and properties of Fe-Al sinters obtained during the SHS reaction is presented in this paper. It was found that increasing the uniaxial pressing pressure led to the increase of the contact area between iron and aluminium particles, which improved the conduction and lowered heat losses during the self-propagating high-temperature synthesis (SHS) reaction and thus result with a sintered material with an improved phase homogeneity. On the other hand, an increase in the pressing pressure causes air be trapped in the pores and later on reacts with iron and aluminium to form oxides. In this work, the shrinkage course was analysed at six different pressing pressures: 50, 100, 150, 200, 300 and 400 MPa. The green compacts were then subjected to the PAIS process (pressure-assisted induction sintering) at a temperature of 1000°C under a load of 100 kN for 5 min. Such prepared samples were subjected to density, porosity, and microhardness (HV0.1) measurements. X-ray diffraction phase analysis and SEM observations were performed together with EDS chemical composition measurements. For studied chemical composition of the samples and sample geometry, 200 MPa compacting pressure was found to be optimal in order to obtain the best sample homogeneity.

The paper presents the results of research on the production and application of sintered copper matrix composite reinforced with titaniumcopper intermetallic phases. Cu- Ti composites were fabricated by powder metallurgy. The starting materials for obtaining the sintered composites were commercial powders of copper and titanium. Experiments were carried out on specimens containing 2.5, 5, 7.5 and 10 % of titanium by weight. Finished powders mixtures containing appropriate quantities of titanium were subjected to single pressing with a hydraulic press at a compaction pressure of 620 MPa. Obtained samples were subjected to sintering process at 880 °C in an atmosphere of dissociated ammonia. The sintering time was 6 hours. The introduction of titanium into copper resulted in the formation of many particles containing intermetallic phases. The obtained sinters were subjected to hardness, density and electrical conductivity measurements. Observations of the microstructure on metallographic specimens made from the sintered compacts were also performed using a optical microscope. An analysis of the chemical composition (EDS) of the obtained composites was also performed using a scanning electron microscope. Microstructural investigations by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) showed that after 6 hours of sintering at 880°C intermetallic compounds: TiCu, TiCu2, TiCu4, Ti2Cu3, Ti3Cu4 were formed. The hardness increased in comparison with a sample made of pure copper whereas density and electrical conductivity decreased. The aim of this work was to fabricate copper matrix composites reinforced with titanium particles containing copper- titanium intermetallic phases using powder metallurgy technology and determine the influence of the titanium particles on the properties of the sintered compacts and, finally, analyse the potentials application for friction materials or electric motors brushes.

The methods of making diamond tools have undergone a remarkable development since the invention of synthetic diamond in the mid-1950s. The current review summarises key historical, recent and ongoing trends and developments in sintered diamond tools. The report concentrates on tools used within the stone and construction industries which, being the main consumers of metal-bonded diamond tools fabricated by powder metallurgy (P/M) technology, have always fuelled advances in tool design and production technologies.

Electrochemical Cr coatings doped with diamond nanoparticles were deposited on sintered steels with different carbon contents (0.2-0.8 wt.-%). The mechanical properties of surfaces as hardness and wear resistance increase as compared to the steel substrate. Microcutting and microgridding mechanisms were observed after tribological tests, but also adhesive wear in some areas was observed. X-ray examination indicated that the layer was textured, with the exception of the sample with the highest concentration of diamond nanoparticles in the electrolyte (42 g/l). The intensity ratio ICr110/ICr200 was calculated and compared with the indices for a standard sample. The greatest differences in the intensity ratio occurred for the samples with low carbon content (0.2%C). On the other hand, more the material is textured the greater the difference.

Kaolin-based geopolymers are alternatives for producing high-strength ceramics for construction materials. Creating high-performing kaolin ceramics utilizing the regular technique requires a high handling temperature (higher than 1200°C). Thus, the structure and properties such as pore size and distribution are affected at higher sintering temperatures. Along these lines, information with respect to the sintering system and related pore structure is essential for advancing the properties of the previously mentioned materials. This study investigated the microstructure and the density of a kaolin-based geopolymer at various sintering temperatures. The unsintered sample has the highest density of 1610 kg/cm3, while the samples sintered at 1100°C haves the lowest density of 1203 kg/cm3. The result also shows that increasing the sintering temperature to 1100°C resulted in increasing the water absorption of the kaolin-based geopolymer ceramic.

The paper refers to pulverization and sintering of the (Fe80Nb6B14)0.88Tb0.12 high coercive alloy. The powder was sintered using the ultra-fast current aided method. It turned out that too long discharge time leads to appearing of a soft magnetic phase and simultaneously, decrease in coercivity of the compacted powder. Nevertheless, it was possible to establish preference technology parameters, preserving magnetic hardness of the alloy. As a final test, an impact of Co-powder addition on magnetic properties was studied. The introduced soft magnetic phase (about 20 wt. %) caused about 30% increase of magnetic remanence, which is a result of direct exchange interactions between the two phases.

Microwave sintering process was employed to agglomerate ferromanganese alloy powders. The effects of sintering temperature, holding time and particle size composition on the properties and microstructure of sintering products were investigated. The results was shown that increasing sintering temperature or holding time appropriately is beneficial to increase the compressive strength and volume density. SEM and EDAX analysis shows that the liquid phase formed below the melting point in the sintering process, which leads to densification. XRD patterns indicate that the main reaction during microwave sintering is the decarbonization and carburization of iron carbide phase. The experiment demonstrate that the optimum microwave sintering process condition is 1150°C, 10 min and 50% content of the powders with the size of –75 μm

Usually porous metals are known as relatively excellent characteristic such as large surface area, light, lower heat capacity, high toughness and permeability for exhaust gas filter, hydrogen reformer catalyst support. The Ni alloys have high corrosion resistance, heat resistance and chemical stability for high temperature applications. In this study, the Ni-based porous metals have been developed with Hastelloy powder by gas atomization and water atomization in order to find the effects of powder shape on porous metal. Each Hastelloy powder is pressed on disk shape of 2 mm thickness with 12 tons using uniaxial press machine. The specimens are sintered at various temperatures in high vacuum condition. The pore properties were evaluated using Porometer and microstructures were observed with SEM.

439L stainless steel composites blended with fifteen micron SiC particles were prepared by uniaxial pressing of raw powders at 100 MPa and conventional sintering at 1350oC for 2 h. Based on the results of X-ray diffraction analysis, dissolution of SiC particles were apparent. The 5 vol% SiC specimen demonstrated maximal densification (91.5%) among prepared specimens ­(0-10 vol% SiC); the relative density was higher than the specimens in the literature (80-84%) prepared by a similar process but at a higher forming pressure (700 MPa). The stress-strain curve and yield strength were also maximal at the 5 vol% of SiC, indicating that densification is the most important parameter determining the mechanical property. The added SiC particles in this study did not serve as the reinforcement phase for the 439L steel matrix but as a liquid-phase-sintering agent for facilitating densification, which eventually improved the mechanical property of the sintered product.

One of the ways to decrease thermal conductivity is nano structurization. Cobalt triantimonide (CoSb3) samples with added indium or tellurium were prepared by the direct fusion technique from high purity elements. Ingots were pulverized and re-compacted to form electrodes. Then, the pulsed plasma in liquid (PPL) method was applied. All materials were consolidated using rapid spark plasma sintering (SPS). For the analysis, methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) with a laser flash apparatus (LFA) were used. For density measurement, the Archimedes’ method was used. Electrical conductivity was measured using a standard four-wire method. The Seebeck coefficient was calculated to form measured Seebeck voltage in the sample placed in a temperature gradient. The preparation method allowed for obtaining CoSb3 nanomaterial with significantly lower thermal conductivity (10 Wm^–1K^–1 for pure CoSb₃ and 3 Wm^–1K^–1 for the nanostructured sample in room temperature (RT)). The size of crystallites (from SEM observations) in the powders prepared was about 20 nm, joined into larger agglomerates. The Seebeck coefficient, α, was about –200 µVK^–1 in the case of both dopants, In and Te, in microsized material and about –400 µVK^–1 for the nanomaterial at RT. For pure CoSb3, α was about 150 µVK^–1 and it stood at –50 µVK^–1 for nanomaterial at RT. In bulk nanomaterial samples, due to a decrease in electrical conductivity and inversion of the Seebeck coefficient, there was no increase in ZT values and the ZT for the nanosized material was below 0.02 in the measured temperature range, while for microsized In-doped sample it reached maximum ZT = 0.7 in (600K).

Tungsten heavy alloys comprising tungsten, nickel and ferrous were modified, where molybdenum was added in varying weight proportions keeping the ratio of Ni: Fe (8:2) constant. The powders were mixed in a high-energy ball mill and were further fabricated using the spark plasma sintering (SPS) method at a peak temperature of 1000°C with heating rate of 100°C/min. The details of the microstructure and mechanical properties of these various alloy compositions were studied. With the increasing weight composition of the Mo in the alloy, the relative density of the alloy increased with a significant improvement in all the mechanical properties. The yield strength (YS), ultimate tensile strength (UTS) and hardness improved significantly with increase in the proportion of Mo; however, a reduction in elongation percentage was observed. The maximum strength of 1250 MPa UTS was observed in the alloy with a Mo proportion of 24%. The heavy alloy unmixed with Mo has shown distinct white and grey regions, where white (W) grain is due to tungsten and grey region is a combinatorial effect of Ni and Fe. Upon addition of Mo, the white and gray phase differences started to minimize resulting in deep gray and black ‘C’-phase structures because of homogenization of the alloy. The main fracture mode found during this investigation in the alloys was inter-granular mode.

The mechanical behavior and the change of retained austenite of nanocrystalline Fe-Ni alloy have been investigated by considering the effect of various Ni addition amount. The nanocrystalline Fe-Ni alloy samples were rapidly fabricated by spark plasma sintering (SPS). The SPS is a well-known effective sintering process with an extremely short densification time not only to reach a theoretical density value but also to prevent a grain growth, which could result in a nanocrystalline structures. The effect of Ni addition on the compressive stress-strain behavior was analyzed. The variation of the volume fraction of retained austenite due to deformation was quantitatively measured by means of x-ray diffraction and microscope analyses. The strain-induced martensite transformation was observed in Fe-Ni alloy. The different amount of Ni influenced the rate of the strain-induced martensite transformation kinetics and resulted in the change of the work hardening during the compressive deformation.

The Polish basis of dolomites is remarkable. Their total reserves reported in the 62 deposits listed in current data bases of mineral resources amount to 1,500,000 t. However, there is a shortage of the so-called converter dolomites of high quality applicable in manufacturing of refractory materials. Such dolomites of the Triassic age have been quarried for many years in the Brudzowice and Ząbkowice Śląskie I deposits in the Silesian-Cracow region. The Libiąż deposit is perspective of this area, considering the character and properties of its dolomites. The dolomites of the Nowa Wioska and Stare Gliny deposits belong into the same group although their applying as refractories seems to be disputable at the moment and would require more detailed analyses of the chemical composition and firing properties of the rocks mentioned. The reason is that the dolomites of these deposits have been reported andmassively quarried up to now mainly for civil engineering (roads, buildings, etc.). Unfortunately, worsening properties of the dolomites occurring in Żelatowa, still another large and developed deposit of the region, have been excluded using these rocks in producing of refractories. Among the group of reserve converter dolomite deposits, the best rock properties have been found in four of them, i.e., Chruszczobród, Chruszczobród I, Chruszczobród II and Libiąż Wielki. The survey presented indicates that there are some possibilities of including dolomites of the Winna and, to a lesser degree, Radkowice-Podwole deposits as the raw materials in manufacturing of refractories. Again, more detailed analyses of the chemical composition and petrographical development, mainly of the grain size distribution, would be required. Dolomitic marbles of the Lower Silesia region represent a separate problem. Traditionally, they have been considered to be non-applicable in manufacturing of refractories because of too coarse grain size of these rocks. It should be stressed, however, that the Lower Silesian marbles occur in several varieties and among them also fineand coarse-grained dolomites occur. Their finest and chemically purest varieties can be an interesting option in extending the basis of refractory dolomitic raw materials in Poland, although selective quarrying would be required in such a case.

Research in additive manufacturing of tungsten carbide-cobalt has intensified over the last few years due to the increasing need for products designed using topology optimisation and multiscale structures (lattice). These products result in complex shapes and contain inner structures that are challenging to produce through conventional techniques, thus involving high costs. The present work addresses this problem using a two-step approach to 3D print parts with complex shapes and internal structures by employing indirect selective laser sintering (SLS) and tungsten carbide-cobalt sintering. The paper takes further our research in this field [1] to improve the part density by using high bulk density tungsten carbide-cobalt powders. Mechanically mixing tungsten carbide-cobalt with the sacrificial binder, polyamide 12, results in a homogenous powder successfully used by the selective laser sintering process to produce green parts. By further processing, the green parts through a complete sintering cycle, an average final part density of 11.72 g/cm3 representing more than 80% of the theoretical density is achieved.

In the present paper, elemental Fe, Cr and Ni powders were used to fabricate nano-structured duplex and ferritic stainless steel powders by using high energy planetary ball milling. We have studied the effect of milling atmosphere like wet (toluene) and dry (argon) milling of elemental Fe-18Cr-13Ni (duplex) and Fe-17Cr-1Ni (ferritic) powders for 10 h in a dual drive planetary mill. Stearic acid of 1wt. % was added during milling to avoid agglomeration. The dry and wet milled duplex and ferritic stainless steel powders were characterized by XRD, SEM and particle size analysis techniques. We have found that both the milling atmospheres have great influence in controlling the final particle morphology, size and phase evolution during milling. It was reported that dry milling is more effective in reducing particle size than the wet milling. The Nelson-Riley method of extrapolation was used to calculate the precise lattice parameter and Williamson-Hall method was used to calculate the crystallite size and lattice strain of both the stainless steel milled in argon atmosphere. Dry milled duplex and ferritic stainless steel were then consolidated by conventional sintering method at 1100, 1200 and 1300°C temperatures under argon atmosphere for 1 hour.