G. Matula

Effect of Manufacturing Methods on Structure and Properties of the Gradient Tool Materials with the Non-Alloy Steel Matrix Reinforced with the HS6-5-2 Type High-Speed Steel

Investigations carried out referred to obtaining material based on the high-speed steel and non-alloy steel. The conventional powder metallurgy method was used for manufacturing these materials, consisting in compacting the powder in the closed die and sintering it next, the isostatic pressing method, and the modern pressureless forming powder metallurgy. Forming methods were developed during the investigations for high-speed and non-alloy steel powders, making it possible to obtain materials with three layers in their structure. Investigations included determining the sintering conditions, and especially the temperature and treatment cycle, as well as examining the selected mechanical properties. It was found out, basing on the comparison of structures and properties of test pieces made with the pressureless forming method, as well as with the isostatic pressing and pressing in the closed die, with further sintering, that in structures of all examined test pieces in the sintered state fine carbides occurred distributed homogeneously in the high-speed steel layer. It was noticed, that increase of the sintering temperature, regardless of the manufacturing method, results in the uncontrolled growth and coagulation of the primary carbides and melting up to forming of eutectics in layers consisting of the high-speed steel. It was found out basing on the microhardness tests that hardness of test pieces both those pressureless formed, compacted in the closed die, and isostatically cold pressed and sintered grows along with the sintering temperature. It was also noted that the sintering temperature range is bigger in case of the pressureless formed materials.

Effect of Laser Surface Melting on Structure and Properties of a High Speed Tool Steel

The purpose of this research paper is focused on the high speed steel surface layers improvement properties using HPDL laser. The paper present laser surface technologies, investigation of structure and properties of the high speed steel alloying with carbides using high power diode laser HPDL. Investigation indicate the influence of the alloying carbides on the structure and properties of the surface layer of investigated steel depending on the kind of alloying carbides and power implemented laser (HPDL). In the effect of laser alloying with powder of carbides occurs size reduction of microstructure as well as dispersion hardening through fused in but partially dissolved carbides and consolidation through enrichment of surface layer in alloying additions coming from dissolving carbides. Introduced particles of carbides and in part remain undissolved, creating conglomerates being a result of fusion of undissolved powder grains into molten metal base. The structural mechanism was determined of surface layers development, effect was studied of alloying parameters, gas protection method, and thickness of paste layer applied onto the steel surface on structure refinement and influence of these factors on the mechanical properties of surface layer, and especially on its hardness, abrasive wear resistance, and roughness. It has the important cognitive significance and gives grounds to the practical employment of these technologies for forming the surfaces of new tools and regeneration of the used ones.

Influence of Binders on the Structure and Properties of High Speed-Steel HS6-5-2 Type Fabricated Using Pressureless Forming and PIM Methods

Based on the comparison of structures and properties of the HS6-5-2 high speed steels made with the powder injection moulding method, pressureless forming, compacting and sintering, and commercial steels made with the ASEA-STORA method, fine carbides spread evenly in the steel matrix were found in the structure of all tested high-speed steels in the sintered state. The use of a nitrogen atmosphere in the sintering process, causes the formation of fine, spherical MX type carbonitrides, stable in high sintering and austenitizing temperatures. The steels made with the pressureless forming method are characteristic of the lowest sintering temperature and the highest density, resulting from the high carbon concentration coming from the binding agent degradation. Moreover, the higher carbon concentration causes an increase in the retained austenite portion and a lower hardness after quenching and tempering. The heat-treated injection moulded steel attains hardness comparable to the commercial ASP23 type one, demonstrating the well-founded reasons for using the powder-injection moulding method for manufacturing the high-speed steel. The powder-injection moulding makes manufacturing tools possible with their final shape, i.e., leaving out the plastic forming and machining which is necessary for instance in case of the ASP 23 type steel. Furthermore, the degradation and sintering process time of the injection moulded steels is approximately 10h shorter than for steels made with pressureless moulding, which is due to the use of a two-component binding agent.

Fabrication Technologies of the Sintered Materials Including Materials for Medical and Dental Application

This chapter of the book presents the basis of classical powder metallurgy technolo‐ gies and discusses powder fabrication, preparation, preliminary moulding, sintering and finish treatment operations. A general description of the materials and products manufactured with the classical powder metallurgy methods is presented. New variants are characterised along with special and hybrid technologies finding their applications in powder metallurgy. Special attention was drawn to microporous titanium and to TiAl6V4 alloy fabricated using hybrid rapid manufacturing technologies with selective laser sintering/selective laser melting (SLS/SLM) used for innovative implant scaffolds in medicine and regenerative dentistry. Laser deposition, thermal spraying and detonation spraying of powders are also discussed as special methods in which powders of metals and other materials are used as raw materials.

Comparison of Structure and Properties of Hard Coatings on Commercial Tool Materials Manufactured with the Pressureless Forming Method or Laser Treatment

The goal of the work is fabrication coatings with the pressureless forming method or laser treatment retaining the relatively high ductility of the coated tools core. The paper presents selection of the binder portion and type, and also of the metallic and carbides powders (WC) being the constituents of the polymer-powder slurry which was applied onto the prepared surfaces of the test pieces from the conventional HS6-5-2 high speed steel. This materials was compared with the same conventional HS6-5-2 high speed steel heat-treatable steel after laser treatment conditions and alloying additions contained in WC. Investigation indicate the influence of the alloying carbides on the structure and properties of the surface layer of investigated steel depending on manufacturing conditions and power implemented laser (HPDL). In the effect of laser alloying with powders of carbides occurs size reduction of microstructure as well as dispersion hardening through fused in but partially dissolved carbides and consolidation through enrichment of surface layer in alloying additions coming from dissolving carbides. The resistivity to thermal fatique of laser remelted steel is higher than steel after heat treatment. It shows the possibility of applying the worked out technology to manufacturing or regeneration of chosen hot working tools.

Influence of cobalt portion on structure and properties of FGHM

The purpose of this paper was characterisation of the structure and properties of functionally gradient hardmetals manufactured by P/M method on the basis of cobalt matrix. The distribution of functionally gradient hardmetals porosity was made using image analysis on the light microscope. Hardness tests of all layers in the sintered test pieces were made with the Vickers method. Density of sintered samples was made using the Archimedes method. In case of the all cemented carbides reinforced with different ceramics particles fabricated, it was found that density of sintered samples depend on reinforced particles. Moreover, density of sintered samples depend on temperatures and atmosphere of sintering process. The investigation results will provide useful information in applying the Powder Metallurgy to manufacturing functionally gradient hardmetals on the basis of cobalt matrix. The project contributes to improving of tool cutting material properties through manufacturing of functionally gradient hardmetals by P/M method. [Received on 15 November 2006; Accepted on 12 February 2007]

Effects of chromium carbide on the microstructures and wear resistance of high speed steel obtained by powder injection moulding route

ABSTRACT The effects of chromium carbide on the microstructures and wear resistance of high speed steel were studied. Metal matrix composites (MMCs), based on M2 high speed steel reinforced with different percentages of Cr3C2, were produced following a metal injection moulding route: feedstock manufacturing, injection, debinding and sintering. The weight fraction of hard second phase particles in tool steels is limited by the formation of large interconnected carbides that embrittle the alloy. Additions of up to 14 wt-% Cr3C2 were successfully prepared. The influence of the chromium carbide content on the optimum sintering temperature was analysed. The mechanical properties of the sintered composites were obtained by measuring hardness and wear behaviour. Microstructure and wear mechanisms were investigated by means of scanning electron microscopic observations. These results, together with X-ray diffraction characterisation and EDS analysis, allow explanation of the mechanisms responsible for the wear behaviour. This paper is part of a special issue on the Advances in Materials and Processing Technologies (AMPT) 2015 and has subsequently been revised and extended before publication in Powder Metallurgy.

Composite Materials Infiltrated by Aluminium Alloys Based on Porous Skeletons from Alumina, Mullite and Titanium Produced by Powder Metallurgy Techniques

The infiltration technology with reinforcement in the form of porous skeletons fabricated with powder metallurgy methods has been presented in relation to the general characteristics of metal alloy matrix composite materials. The results of our own investigations are presented pertaining to four alternative technologies of fabrication of porous, sintered skeletons, and their structure and their key technological properties are presented. Porous skeletons made of Al2O3 aluminium are sintered reactively using blowing agents or are manufactured by ceramic injection moulding (CIM) from powder. Porous skeletons made of 3Al2O3⋅2SiO2 mullite are achieved by sintering a mixture of halloysite nanotubes together with agents forming an open structure of pores. Titanium porous skeletons are achieved by selective laser sintering (SLS). The structure and properties of composite materials with an aluminium alloy matrix—mainly EN ACAlSi12 and also EN AC-AlSi7Mg0.3 alloys—reinforced with the so manufactured skeletons are also described. A unique structure of the achieved composite materials, together with good mechanical properties and abrasive wear resistance at low density, ensured by an aluminium alloy matrix, are indicating broad application possibilities of such composites.

Role of Halloysite Nanoparticles and Milling Time on the Synthesis of AA 6061 Aluminium Matrix Composites

The aim of this work is to determine the effect of a reinforcing phase and manufacturing conditions on the structure and properties of newly developed nanostructural powders of composite materials with the aluminium alloy matrix reinforced with natural halloysite nanotubes. Composite materials were manufactured employing as a matrix the air atomized powders of AA 6061 aluminium alloy and as a reinforcement the halloysite nanotubes. Composite powders of aluminium alloy matrix reinforced with 5, 10 and 15 wt.% of halloysite nanotubes were fabricated by high-energy mechanical alloying using a planetary mill. Elaborated composite powders were characterized for their apparent density, microhardness, particle size distribution and microstructure. A structure of newly developed nanostructured composite materials reinforced with halloysite nanotubes prove that a mechanical alloying process allow to improve the arrangement of reinforcing particles in the matrix material. A homogenous structure with uniformly arranged reinforcing particles can be achieved by employing reinforcement with halloysite nanotubes if short time of mechanical alloying is maintained thus eliminating an issue of their agglomeration.

Application of an Ant Colony Optimization Algorithm in Modeling the Heat Transfer in Porous Aluminum

In this paper procedure for solving inverse heat conduction problem with fractional derivative is presented. Authors present time fractional heat conduction model with Caputo derivative and Neumann, Robin boundary conditions, which can be applied to describe process of heat conduction in porous media. Based on temperature measurements, functional describing error of approximate solution is created. Considered inverse problem is transform to find minimum of created functional. In order to solve inverse problem (find unknown parameters of model) authors applied an Ant Colony Optimization (ACO) algorithm. Finally, experiment with data from porous aluminum was carried out to check effectiveness of proposed algorithm. Goal of this paper is reconstruction unknown parameters in heat conduction model with fractional derivative and show that ACO is effective algorithm and works well in these type of problems.