Search Results

You are looking at 1 - 10 of 81 items for :

  • hot pressing x
Clear All
Open access

S. Roskosz

Abstract

The aim of this paper is an assessment of the influence of hot isostatic pressing treatment on porosity of cast samples - turbine blades and vane clusters made of the IN713C superalloy. Two variants of HIP treatments, differing in pressure from each other, have been used.

The quantitative evaluation of the porosity was performed using light microscopy and quantitative metallography methods.

The use of the hot isostatic pressing significantly decreased the volume fraction and size of pores in the test blades, the remaining pores after the HIP process being characterized by a round shape. The increased pressure has caused significant reductions in the area fraction and size of the pores.

Open access

M. Ardestani, M. Zakeri, M. Nayyeri and M. Babollhavaejie

Abstract

Ag — 8 wt. % ZnO composites were synthesized by ball milling, heat treating and hot pressing of silver and zinc oxide powder mixtures. The crystalline size and microstrain of the milled powders before and after heat treatment were determined by Debye-Scherrer andWilliamson-Hall methods. It was shown that heat treatment resulted in decrease of microstrain and increase in the crystallite size of the milled powders. The effect of uniaxial pressure magnitude and duration of hot pressing at 550 °C on the final density of the powder compacts were investigated. The results showed that both plastic flow and atomic diffusion mechanisms affected densification of the composite powders during the hot pressing process. However, the latter one had more effective role on the density of the hot-pressed samples. The synthesized composites showed homogenous microstructure with relatively high density and hardness.

Open access

M. Balcerzak and M. Jurczyk

Abstract

Ti2Ni alloy pellets were produced by mechanical alloying and hot pressing at 750°C for 0.5 h in vacuum. X-ray diffraction analysis showed that, after 8 h of milling, a starting mixture of elements mostly decomposed into an amorphous phase. Obtained powders and flakes have cleavage fracture morphology with huge number of dimples with different sizes. Hot pressing of materials caused formation of Ti2Ni main phase. Porosity of pellets strongly depended on size of agglomerates and pressure of pressing. Ti2Ni pellets were used as negative electrodes for Ni-MHx batteries. Maximum measured discharge capacity of studied materials was 220 mAh/g. Electrochemical properties resulted from size of agglomerates, degree of oxidation and pressure of pressing.

Open access

M. Suśniak, J. Karwan-Baczewska, J. Dutkiewicz, M. Actis Grande and M. Rosso

Abstract

The present work investigates the possibility of using powder metallurgy processing for producing a metal matrix composite. Materials were prepared from AlSi5Cu2 chips with reinforcement of 10, 15, 20 wt. % silicon carbide. Aluminum alloy chips were milled with SiC powder in a high-energy ball mill by 40 hours. Mechanical alloying process lead to obtain an uniform distribution of hard SiC particles in the metallic matrix and refine the grain size. The consolidation of composite powders was performed by vacuum hot pressing at 450°C, under pressure of 600 MPa by 10 min. The results shows that the addition of SiC particles has a substantial influence on the microstructure and mechanical properties of composite powder as well as consolidated material. Hot pressing is an effective consolidation method which leads to obtain dense AlSi5Cu2/SiC composite with homogeneous structure and advanced mechanical properties.

Open access

B. Kościelniak, S. Roskosz and J. Cwajna

Abstract

The IN713C is nickel-based superalloy, used to produce low pressure turbine blades in a process of investment casting. However, porosity which is formed during the casting, decreases mechanical properties of IN713C. Therefore, to eliminate porosity, a process of hot isostatic pressing was applied. Nonetheless, HIP also least to some changes in the microstructure of tested material. The main aim of this paper is to characterize the morphology of carbides before and after hot isostatic pressing. Microstructural characterization was carried out with the use of a scanning electron microscope equipped with an energy dispersive X-ray spectrometer and an electron backscatter diffraction detector. The size and shape of carbides were evaluated by quantitative metallography methods methods. The results show that the amount, size and heterogeneity of arrangement of the carbides increased after application of HIP treatment.

Open access

J. Borowiecka-Jamrozek and J. Lachowski

Polish). [5] Borowiecka-Jamrozek, J. (2013). Engineering structure and properties of materials used as a matrix in diamond impregnated tools. Archives of Metallurgy and Materials. 58(1), 5-8. DOI: 10.2478/v10172-012-0142-0 [6] Rimlinger, S. (1999). Cobalt and cobalt – containing binders for the diamond tools industry. The cobalt conference, The Royal Garden Hilton, London, England, 144. [7] Konstanty, J. & Bunsch, A. (1991). Hot pressing of cobalt powders. Powder Metallurgy. 34(3), 195-198. [8] Borowiecka-Jamrozek, J. & Konstanty, J. (2014

Open access

Kamil Kornaus, Agnieszka Gubernat, Dariusz Zientara, Paweł Rutkowski and Ludosław Stobierski

., Grabowski, G. & Zientara, D. (2014). Hot pressing of tungsten carbide with and without sintering additives. Int. J. Refract. Met. Hard Mater. 43, 193–199. DOI: 10.1016/j.ijrmhm.2013.12.002.

Open access

D. Kalinski, M. Chmielewski, K. Pietrzak and K. Choregiewicz

Intermetallic phases of the Ni-Al type belong to the group of modern constructional materials which have numerous advantageous properties such as high melting temperature, low density, high resistance to high-temperature oxidation (to about 1200°C), high mechanical strength, high fatigue strength, and high tensile and compressive strength (also at elevated temperatures). Intermetallic compounds have however also drawbacks in that they are quite brittle at room temperature which makes their mechanical processing very difficult and restricts their application range. These drawbacks can be obviated by modifying their chemical composition. Improving the properties of NiAl-based materials can be achieved by creating the composite with the matrix made of an intermetallic phase NiAl reinforced with ceramic (Al2O3) particles.

This paper is concerned with the mechanical and physical properties (bending strength, fracture toughness, hardness, and Young modulus) and also the microstructure of NiAl/Al2O3 composite. The composite materials were produced by the hot-pressed method using the NiAl/20%Al2O3 (vol.%) powder mixtures. The composite thus produced had a high density of about 99% of the theoretical value and a high bending strength. The bending strength of the NiAl/20vol.%Al2O3 composite was higher by about 80% (635 MPa) than that of the pure NiAl phase (345 MPa). The experiments included also the examination of the effect of the rotational speed of the mill and the duration of the mixing process upon the size and distribution of grains, the microstructure, and phase composition of the composite powder mixtures obtained.

Open access

B. Bruś and A. Zarycka

Abstract

The aim of this work was to characterize the microstructure of LMO type ceramics. The ceramics obtained by the free sintering at two temperatures 1473 K and 1573 K and two sintering times 6 and 12 h was the test material. One series was also obtained by the hot pressing method for a comparison. In all the cases the material synthesis was conducted by the solid-state reaction method at 1173 for 24 h. Photographs of the specimen fractures were taken by a scanning electron microscope to characterize the microstructure of the ceramics obtained in a more detailed way. The VISILOG 4 system, enabling to calculate a lot of parameters characterizing the material microstructure, such as e.g.: a number of grains on the unit area, an average grain size, shape indexes of the grains in question, was used as well. It allows determining a grain size distribution, and a frequency of presence of grains with the specific shape index.

By analyzing a set of the parameters obtained an influence of the technological conditions on the microstructure of the material in question, and on its properties and applicability at the same time can be determined.

Open access

J. Borowiecka-Jamrozek

Abstract

This paper presents results of investigations of WC-12%Co and WC-17%Co coatings detonation sprayed on a sintered cobalt substrate.

The main objective of the present work was to establish a new production route of sandwich type diamond-impregnated segments for circular sawing of stone and other construction materials.

Unalloyed cobalt was chosen as the substrate material. Prior to coating the specimens were made by means of hot pressing of Extrafine cobalt powder in a graphite mould.

The segments were then coated with WC-Co. The effects of the coating process on the thickness, microhardness, microstructure and wear resistance of the deposits were investigated.

The properties of the coatings were established by performing the following tests: a microstructure analysis, a point analysis of chemical composition and a linear analysis, a phase composition, a microhardness tests and abrasion resistance.