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The oxidation kinetics and microstructure characteristics of oxide scales thermally grown on the surface of developed FeCr alloy were investigated at 900 °C. The influence of difference sintering technique, i.e. spark plasma sintering and hot pressing, to improve nanostructured alloy performance was studied. The La-implantation was also considered in this study. It was found that the SPS sintered sample showed better performance than the HP sintered sample. Moreover, it also found that a combining of La-implantation and nanostructured alloy was most beneficial. While nanostructured alloy reduced the oxidation rate, the La-implantation increased the Cr₂O₃ scale conductivity.

This study aims to investigate the friction coefficient of Al2O3–NbC nanocomposite obtained by spark plasma sintering sliding against a steel ball.

Tribological tests were carried out using a reciprocating nanotribometer in a ball on flat configuration with normal loads in the range from 10 to 100 mN under dry conditions. Surface changes were analyzed by confocal microscopy and 3D profilometry.

The values of the friction coefficient varied from 0.15 to 0.6 and are independent of the applied load.

The tribological behavior is attributed to fracture in the contact region and the effect of wear debris.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0356/

The corrosion resistance of copper and copper-ruthenium alloys produced by powder metallurgy (spark plasma sintering process) and exposed in 2M sulphuric acid at 45°C and 65°C was investigated using scanning electron microscopy and potentiodynamic polarisation technique.

The small additions of ruthenium (0.5, 1 and 2 Wt.%) to the copper resulted in improved corrosion resistance of the copper alloy by up to 90 per cent when compared to casted copper.

All the sintered copper and copper alloys proved to have increased the corrosion resistance in all the temperatures.

Powder metallurgy was used in achieving these improvements.

Porous implant surface is shown to facilitate bone in-growth and cell attachment, improving overall osteointegration, while providing adequate mechanical integrity. Recently, biodegradable material possessing such superior properties has been the focus with an aim of revolutionizing implant’s design, material and performance. This paper aims to present a comprehensive investigation into the design and development of low elastic modulus porous biodegradable Mg-3Si-5HA composite by mechanical alloying and spark plasma sintering (MA-SPS) technique.

This paper presents a comprehensive investigation into the design and development of low elastic modulus porous biodegradable Mg-3Si-5HA composite by MA-SPS technique. As the key alloying elements, HA powders with an appropriate proportion weight 5 and 10 are mixed with the base elemental magnesium (Mg) particles to form the composites of potentially variable porosity and mechanical property. The aim is to investigate the performance of the synthesized composites of Mg-3Si together with HA in terms of mechanical integrity hardness and Young’s moduli corrosion resistance and in-vitro bioactivity.

Mechanical and surface characterization results indicate that alloying of Si leads to the formation of fine Mg2 Si eutectic dense structure, hence increasing hardness while reducing the ductility of the composite. On the other hand, the allying of HA in Mg-3Si matrix leads to the formation of structural porosity (5-13 per cent), thus resulting in low Young’s moduli. It is hypothesized that biocompatible phases formed within the composite enhanced the corrosion performance and bio-mechanical integrity of the composite. The degradation rate of Mg-3Si composite was reduced from 2.05 mm/year to 1.19 mm/year by the alloying of HA elements. Moreover, the fabricated composites showed an excellent bioactivity and offered a channel/interface to MG-63 cells for attachment, proliferation and differentiation.

Overall, the findings suggest that the Mg-3Si-HA composite fabricated by MA and plasma sintering may be considered as a potential biodegradable material for orthopedic application.

This paper aims to study the microstructural hot corrosion behaviour of the sintered Y₂SiO₅ ceramic silicate under a Na₂SO₄ + V₂O₅ mixture at an engine representative temperature of 1150°C. Y₂SiO₅ is a promising candidate for thermal barrier coatings (TBC) due to its excellent chemical stability at high temperatures. As a continuous source of Y₃+, it is expected that Y₂SiO₅ environmental barrier coating may prolong the lifetime of TBC systems by stopping the degradation caused by the loss of the Y₂O₃ stabilizer.

Two routes were chosen for the yttria silicate powder synthesis by sol-gel from TEOS and APTES precursors as the difference in Si source changed the ratio of Y₂SiO₅/Y₂Si₂O₇ phases. Hot corrosion studies using Na₂SO₄ and V₂O₅ mixtures were conducted on both surfaces of APTES and TEOS tablets at 1150°C for 8 h in atmospheric air. The morphology and microstructure analyses of the silicate samples after hot corrosion tests were carried out using a SEM and X-ray diffraction analyse techniques.

Based on the degradation, the general status of the APTES tablet after hot corrosion presents a better hot corrosion resistance at a temperature of 1150°C than does that of the TEOS tablet. In the TEOS tablet, the crystal morphology of NaY9Si60O26 woodchip shapes with a size of 60 µm is developed on the surface for finally initiating some cracks. In the APTES case, the crystal morphology of rod-like shapes with a size of 100 µm is developed; hence, a dense thick layer predominately postpones the reaction of V₂O₅ and Na₂SO₄ with yttria silicate, and consequently, less damage is observed.

Coating yttria silicate preparation is very complicated; the problems of a high synthesis temperature, long production period and low yield still need to be solved. Under these perspectives, ceramics prepared via spark plasma sintering (SPS) can reach theoretical high densities and a fine grain size can be retained after the SPS process; hence, well resistance to the corrosion in molten salts is expected to obtain for the sintered yttria silicate tablets.

This paper aims to investigate the effect of fly ash reinforcement ratio (Rr) and sintering temperature (T) on the transverse rupture strength (TRS), hardness and density of fly ash reinforced bronze-based composite materials by using multi-objective Taguchi technique, analysis of variance (ANOVA) and regression analysis.

The bronze-based composite materials containing 5, 10 and 15 Wt.% fly ashes were prepared by using spark plasma sintering carried out under a pressure of 35 MPa, at 750, 800 and 850 °C for 3 min. Sintering temperature and fly ash reinforcement ratio were considered as input parameters; the TRS, hardness and density were considered as output parameters. Experiments were designed according to Taguchi L9 orthogonal array. Multi signal-to-noise ratio (MSNR) was computed to define the optimal process parameters. ANOVA was conducted to detect the importance of the input parameters for the process performance. Moreover, the linear model was developed for predicting the performance parameters by using regression analysis.

Fly ash can be a good alternative as reinforcement to reduce the cost for composite materials. Optimal process parameters had obtained 850°C sintering temperature and 5 per cent reinforcement ratio by using multi-objective Taguchi technique. The per cent contributions of the control factors on the performance parameters had obtained sintering temperature (95.78 per cent) and fly ash reinforcement ratio (3.00 per cent) with ANOVA. The obtained results indicate that the sintering temperature was found to be the dominant factor among controllable factors. However, the reinforcement ratio showed an insignificant effect.

It has been indicated that multi-objective Taguchi technique and regression analysis are effective and powerful tools in modeling and simultaneous optimization of quality characteristics for composite materials.

During the operation of nickel-based alloys as blades and discs in turbines, the sliding activity between metallic surfaces is subjected to structural and compositional changes. In as much as friction and wear are influenced by interacting surfaces, it is necessary to investigate these effects. This study aims to understand better the mechanical and tribological characteristics of Ni-17Cr-10X (X = Mo, W, Ta) ternary alloy systems developed via spark plasma sintering (SPS) technique.

Nickel-based ternary alloys were fabricated via SPS technique at 50 MPa, 1100 °C, 100 °C/min and a dwell time of 10 mins. Scanning electron microscopy, X-Ray diffraction, energy dispersive X-ray spectroscopy, nanoindentation techniques and tribometer were used to assess the microstructure, phase composition, elemental dispersion, mechanical and tribological characteristics of the sintered nickel-based alloys.

The outcome of the investigation showed that the Ni-17Cr10Mo alloy exhibited the highest indentation hardness value of 8045 MPa, elastic modulus value of 386 GPa and wear resistance. At the same time, Ni-17Cr10W possessed the least mechanical and wear properties.

It can be shown that the SPS technique is efficient in the development of nickel-based alloys with good elemental distribution and without defects such as segregation of alloying elements, non-metallic inclusions. This is evident from the scanning electron microscopy micrographs.

The purpose of this paper is to investigate the tribological performance of Cr₃C₂–NiCr–Mo–BaF₂ composite sliding against a Si₃N₄ ball at high temperatures.

A Cr₃C₂–NiCr composite and a Cr₃C₂–NiCr–Mo–BaF₂ composite were prepared using spark plasma sintering. Tribological properties of the composites were investigated using a ball-on-disk type tribotester. The relationships among the microstructure, wear mechanism and tribological performance were determined by analyzing the wear track morphologies and the glaze layer’s phase composition.

The wear rate of the Cr₃C₂–NiCr–Mo–BaF₂ composite was approximately one order of magnitude lower than that of the Cr₃C₂–NiCr composite from 700°C to 900°C when sliding against a Si₃N₄ ball. The favorable tribological performance of the Cr₃C₂–NiCr–Mo–BaF₂ composite at high temperatures results from the synergistic lubrication of MoOx, BaF₂ and BaMoO₄.

This paper reports a new Cr₃C₂–NiCr matrix self-lubricating composite with better tribological properties than Cr₃C₂–NiCr composite at temperatures up to 900°C through Mo and BaF₂ addition.

Titanium alloys and composites have proven to contain desirable properties for use at elevated temperatures. One such material is the Ti750 composite, which can be used at temperatures up to 750°C for a brief period. This paper aims the microstructure, phase compositions, apparent porosity and hardness of both sintered and heat-treated TiC reinforced Ti750 composites for consideration in aircraft engine design.

The fabrication of TiC-reinforced Ti750 composites was achieved through spark plasma sintering (SPS). To analyze the microstructure and X-ray diffraction, a scanning electron microscope (SEM) with model number S-3400N and a D8 advance model machine were used, respectively. The microhardness of the samples was measured using a Vickers hardness tester with model HV-1000. The research incorporated three solid solution treatments: 975°C/3 h/AC, 1,010°C/3 h/AC and 1,025°C/3 h/AC, along with a solid-solution aging treatment at 1,010°C/3 h/AC + 750°C/8 h/AC. Additionally, oxidation analysis was conducted on the samples.

The microstructures contained enhanced TiC and Ti5Si3 phases in the near a-Ti matrix. The microhardness of the sintered composite was over twice that of the matrix alloy, and its porosity was reduced by about 0.35%. The sample treated at 1,010°C/3 h/AC had the highest enhanced peaks and microhardness of 1,277.1 HV. After oxidation at 800°C for 100 h, the accumulated weight of the solid solution composite at 1,010 °C/3 h/AC was the lowest (3.0 mg.cm^-2). The surface microstructure contained oxides of TiO2 and a spalling white area containing a small amount of Al₂O₃ and SiO₂.

There is limited research on Ti-Al-Sn-Zr-Mo-Si-based TMCs using a combination of the SPS method. This study used SiCp as a reinforcement for the Ti750 matrix alloy. The consolidation of SiCp and Ti750 powders using the SPS method, heat treatment of the resulting TiC reinforced Ti750 composites and study of the microstructure and properties of the composites are not found in literature or under consideration for publication in any media.

The purpose of this study is to study the mechanical, tribological and electrical properties of the copper-graphene (Cu-Gn) composites fabricated by a novel rapid tooling technique consist of three-dimensional printing and ultrasonic-assisted pressureless sintering (UAPS).

Four different Cu-Gn compositions with 0.25, 0.5, 1 and 1.5 per cent of graphene were fabricated using an amalgamation of three-dimensional printing and UAPS. The polymer 3d printed parts were used to prepare mould cavity and later the UAPS process was used to sinter Cu-Gn powder to acquire free-form shape. The density, hardness, wear rate, coefficient of friction and electrical conductivity were evaluated for the different compositions of graphene and compared with the pure copper. Besides, the comparison was performed with the conventional method.

Cu-Gn composites revealed excellent wear properties due to higher hardness, and the lubrication provided by the graphene. The electrical conductivity of the fabricated Cu-Gn composites started increasing initially but decreased afterwards with increasing the content of graphene. The UAPS fabricated composites outperformed the conventional method manufactured samples with better properties such as density, hardness, wear rate, coefficient of friction and electrical conductivity due to homogeneous mixing of metal particles and graphene.

The fabrication of Cu-Gn composite freeform shapes was found to be difficult using conventional methods. The novel technique using a combination of polymer three-dimensional printing and UAPS as rapid tooling was introduced for the fabrication of freeform shapes of Cu-Gn composites and mechanical, tribological and electrical properties were studied. The method can be used to fabricate optimized complex Cu-Gn structures with improved wear and electrical applications.