Horea Florin Chicinas

• Doctor of Engineering
• Team Leader at Guhring

This paper presents the effects of aqueous processing of WC–Co powders on their sinterability and mechanical properties. WC–Co powders have been milled in aqueous media (distilled water + corrosion inhibitor). The as-milled samples have been compacted and sintered in vacuum at 1380 °C. The investigations performed on the two components, carbide and...

This paper presents the influence of milling media on the structure and morphology of WC–Co powders for sintered tools. WC–Co powders have been milled in two different organic media, acetone and isohexane. The characterisation of the as-milled samples has been done by Xray diffraction, scanning electron microscopy (SEM) and differential scanning ca...

This paper presents a new approach on the wet attrition of some composite WC-10Co powders by using an aqueous medium instead of the classical organic solvent based processing method. The hard metal powders have been characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser particle size analysis (PSA), Fourier transform in...

This paper presents the results of using an aqueous milling media in comparison with traditional milling routes, as well as the influence of the milling media interaction with powder on the morphology and agglomeration behaviour. Hard Metal powders were milled in four distinct milling media, two of them consisting of traditional milling routes and...

Aqueous suspensions of hard metal powders and their use are known to have significant environmental and economic advantages over the systems employed nowadays using organic solvents. The present research describes developing a novel and less harmful processing route for hard metal production. Aqueous spray drying is convenient for obtaining dried W...

The aim of this work is to obtain Cu-13.5Al-4Ni alloy for use as shape memory alloy by Spark Plasma Sintering (SPS) of mechanically alloyed powder. The study investigates the structural and microstructural changes in terms of crystal parameters, crystallite sizes, and phases evolution during mechanical alloying and spark plasma sintering of Cu-13.5...

This study is focused on the mechanical properties of WC-Co composites obtained via Selective Laser Sintering (SLS) using PA12 as a binder. The as-printed samples were thermally debonded and sintered, first in a vacuum, and then sinter-HIP (Hot Isostatic Pressure) at 1400 °C, using 50 bar Ar, which has led to relative densities up to 66%. Optical m...

This study is focused on the mechanical properties of WC-Co composites obtained via Selective Laser Sintering using PA12 as a binder. The as-printed samples were thermally debonded, and sintered, first in vacuum, and then sinter-HIPed at 1400oC, using 50 bar Ar, which has led to relative densities up to 66 %. Optical metallographic images show a mi...

Fe-base Superalloy/Al2O3 type composite compacts were successfully obtained by spark plasma sintering from mechanically alloyed powders. The superalloy powders without Al2O3 and superalloy/Al2O3 type composites powders with 5 and 10 %vol. Al2O3 were synthesized from elemental powders in a high energy planetary mill. The influence of the milling pro...

Materials consisting of a hard phase, usually WC, and a tough binder, traditionally Co, form the most successful class of composite materials, also known as Hard Metals (HM) or Cemented Carbides. Powder metallurgy routes are employed generally for the production of such [1]. The typical processing route of such materials involves mixing the compone...

A new approach for the manufacturing of cemented carbide parts with a high degree of complexity via indirect selective laser sintering (SLS), using commercial WC-12Co with different amounts of polyamide (PA12) and using low-cost standard equipment is proposed. After debinding, vacuum sintering and sinter-HIP at 1400 °C with 50 bar Ar of the green s...

The influence of the nature of the process control agent (PCA) used in the mechanosynthesis of the magnetite nanoparticles has been studied. The two-step route used here for obtaining nanocrystalline/- nanoparticles Fe3O4 consists of a heat treatment, to prepare well-crystallised magnetite, followed by the mechanosynthesis process. Dry milled magne...

The formation of iron oxide/iron composite compacts using mechanically activated and un-activated α-Fe2O3/Fe powder mixtures in various ratios by reactive spark plasma sintering – SPS is evidenced. Independent on the sintering temperature SPS of activated powders is leading to compacts with a microstructure consisting of iron clusters distributed i...

Nanocrystalline Ni51Mn19Sn30 Heusler alloy was prepared in the form of powder by solid state reaction in a planetary ball mill under argon atmosphere. After 10 h of milling the samples exhibit a mixture of two phases: disordered Heusler structure and half-Heusler structure. The stability of the phases was studied and a transformation of the disorde...

Formation of the Ni2MnSn Heusler alloy by solid state reaction from elemental powders was investigated. The solid state reaction was conducted in a planetary ball mill under argon atmosphere up to 28 h of milling. During the milling, after selected intervals samples were collected and studied by X-ray diffraction to record phase changes. After 16 h...

Fe3O4/Ni3Fe composite powder has been synthetized, starting from Fe, NiO and α-Fe2O3 precursors via mechanosynthesis and annealing, varying the alloy/ferrite ratio. The formation of Fe3O4 is noticed for the composite with low alloy content in the case of the samples milled for 10 hours. Formation of Ni3Fe and Fe3O4 does not fully occur after millin...

This paper presents a comparative study regarding the preparation of Fe-based amorphous alloys via mechanical alloying (MA) and rapid quenching (RQ). The obtained samples (powders and ribbons) were characterised by X-ray diffraction (XRD), in-situ high-temperature X-ray diffraction (HT-XRD), differential scanning calorimetry (DSC), thermogravimetry...

Amorphisation of Fe75Si20B5(at. %) alloy has been attempted both by wet and dry mechanical alloying starting from a mixture of elemental powders. Powder amorphisation was not achieved even after 140 hours of dry mechanical alloying. Using the same milling parameters, when wet mechanical alloying was used, the powder amorphisation was achieved after...

Magnetite (Fe3O4) has been synthesised via a new combined route, ceramic method and mechanical milling, starting from a stoichiometric mixture of the easily accessible Fe and Fe2O3 precursors. In the first step, well crystallised magnetite has been obtained by heat treatment of the precursor homogenised mixture at lower temperature as compared to t...

Oleic acid coated iron ferrite-magnetite nanoparticles (Fe3O4) have been synthesized via a new combined route, ceramic method and subsequent wet mechanical milling, starting from a stoichiometric mixture of the easily accessible Fe and Fe2O3 precursors. In the first step, the magnetite has been obtained in well crystallised state by heat treatment...

Co-based amorphous alloys were prepared via wet mechanical alloying process starting from elemental powders. The reference alloy Co70Fe4Ni2Si15B9 (at. %) as well as the alloys derived from this composition by the substitution of 5 at.% of Zr or Ti for Si or B (Co70Fe4Ni2Si15B4Zr5, Co70Fe4Ni2Si15B4Ti5, Co70Fe4Ni2Si10B9Zr5 and Co70Fe4Ni2Si10B9Ti5) ar...

Amorphous Fe75Si15B5M5 powders with M = Ti, Ta and Zr, were synthesized by mechanical alloying and their thermal stability, crystalline state, particles morphology and magnetic properties were investigated in this study. It is found that the time to achieve amorphisation during milling increases by the substitution of any of the above transition me...

Soft magnetic Fe3O4/Ni3Fe composite powder has been synthetized, starting from Fe, Ni and Fe2O3 powders via mechanosynthesis and subsequent annealing. The incipient formation of Fe3O4 is noticed for the sample milled for 2 h. Formation of Ni3Fe and Fe3O4 does not occur completely after milling for 10 h and as a consequence the presence of a small a...

Nanocrystalline magnetite – Fe3O4 has been synthesized in nanocrystalline state by mechanical milling of well crystallized magnetite samples obtained by heat treatment of a stoichiometric mixture of iron and hematite. Upon increasing the milling time, the mean crystallite size of magnetite is diminishing. After only 5 minutes of mechanical milling...

Result of research concerning the influence of milling conditions on the amorphisation of the Fe75Si20B5 (at.%) alloy is presented. Amorphous powder of Fe75Si20B5 (at.%) was prepared by dry and wet mechanical alloying (MA) route starting from a mixture of Fe, Si and B elemental powders. The mixture was wet/dry milled up to 50 hours. Benzene, oleic...

Amorphous Fe75Si20-xB5Mx powders with M= Ti, Ta or Zr and x = 0 and 5 were synthesized by wet mechanical alloying, using benzene as a surfactant. The thermal stability of the Fe-Si-B alloy increases by introducing transition metals. The replacement of 5% Si with Ti, Ta or Zr leads to an increase of the crystallization temperature. It was found that...