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Papers by Jari Liimatainen

Nordisk Konferens i Pulverteknik 90, 1995

1996 World Congress on Powder Metallurgy & Particulate Materials, 1996

Fusion Engineering and Design, 2005

Abstract Vacuum vessel and plasma facing components of the ITER construction including shield mod... more Abstract Vacuum vessel and plasma facing components of the ITER construction including shield modules and primary first wall panels have great impact on the production costs and reliability of the installation. From the manufacturing technology point of view, accuracy of shape, properties of the various austenitic stainless steel/austenitic stainless steel interfaces or CuCrZr/austenitic stainless steel interfaces as well as those of the base materials are crucial for technical reliability of the construction. The current approach in plasma facing components has been utilisation of solid-HIP technology and solid–powder-HIP technology. Due to the large size of especially shield modules shape, control of the internal cavities and cooling channels is extremely demanding. This requires strict control of the raw materials and manufacturing parameters.

International Conference on Engineering Integrity Assessment, 1994

The EU project SENSIndoor aims at the development of novel nanotechnology based intelligent senso... more The EU project SENSIndoor aims at the development of novel nanotechnology based intelligent sensor systems for selective monitoring of Volatile Organic Compounds (VOC) for demand controlled ventilation in indoor environments. Target gases are benzene, naphthalene and formaldehyde, as these VOCs are highly health relevant and occur in many indoor environments, thus making their monitoring a high priority for safe and healthy buildings. Relevant concentrations according to recommended values given by the WHO are in the low ppb range with benzene requiring the highest sensitivity to achieve a target concentration below 1 ppb. The SENSIndoor project makes use of two novel approaches to achieve this challenging goal: highly porous and well-controlled nano-scaled gassensitive layers deposited by Pulsed Laser Deposition (PLD) as well as selective pre-concentration using Metal-Organic Frameworks integrated on micro hotplates.

Proceedings of the Estonian Academy of Sciences. Engineering, 2006

Steel matrix composites are an attractive choice for paper, pulp and mineral crushing industries ... more Steel matrix composites are an attractive choice for paper, pulp and mineral crushing industries because of their wear resistant properties. In this paper the abrasive wear properties of the tool steel matrix composites are studied. The rubber wheel abrasion tests were carried out using six different composites. The tool steel Ralloy ® WR6 was used as matrix material in all composites. Typically there is about 20 vol% VC in the matrix before the addition of the particle reinforcements. Reinforcements were either cemented carbides (WC-Co), cast tungsten carbides (WC) or niobium carbides (NbC). All the composites were so-called double dispersion composites having two distinctive reinforcement types. Although the wear resistance of the composite materials has been found to increase with reinforcement additions in rock crushing environment with multimode wear conditions, the pure abrasion resistance of the composites, having up to 30% additional reinforcements, was found inferior to the matrix tool steel. Based on the observations it is suggested that in order to improve the abrasive wear resistance of the tool steels by adding hard particles, the matrix-particle interface should be strong enough to prevent the detachment of particles and the amount of particles should be high enough to compensate the accelerated wear of the matrix because of hard particle wear debris.

Wear, 2007

Abrasive wear is the most common type of wear phenomenon in mineral crushing industry. Tool steel... more Abrasive wear is the most common type of wear phenomenon in mineral crushing industry. Tool steel matrix-based composites are an attractive choice to combat wear in those conditions because of their excellent abrasion resistance. One purpose of this study is to evaluate the abrasion resistance of such composites having different microstructures. Another purpose is to find out whether the simple dry sand rubber wheel abrasion test (ASTM G 65-91), which is a commonly used and relatively cheap and easy-to-perform test, could be used to rank materials for rock crushing although abrasive wear is not the only type of wear in the real rock crushing conditions. For this purpose Nordberg laboratory cone crusher test was used. Seven different composites were studied. The tool steel of type Ralloy ® WR6 was used as a matrix material in all composites. The reinforcement was either cemented carbide (WC-Co), cast tungsten carbide (WC) or titanium carbide (TiC). The composites were manufactured by hot isostatic pressing (HIP). Abrasive wear properties of all the studied composites are very good. The reinforcement type, size, properties, volume fraction and reinforcement distribution in the matrix all influenced the wear results in both of the tests, but in a different way. Best wear resistance in cone crusher conditions was obtained with cemented carbide (WC-10Co) reinforced Ralloy ® WR6 and in dry sand abrasion with WC reinforced Ralloy ® WR6. No simple correlations between the dry sand rubber wheel abrasion test results and the cone crusher test results were found. This can be attributed to the different wear mechanics and consequently wear mechanisms in the two tests. In the dry sand rubber wheel abrasion test abrasion and detachment of the reinforcements are the major wear mechanisms while in the cone crusher abrasion with rock sliding and pure indentation are the major wear mechanisms. The differences in wear mechanisms result from differences in abrasives (type, size and hardness) and other wear conditions. It is concluded that dry sand rubber wheel abrasion test should not be used for screening materials for rock crushing applications as far as metal matrix composites are concerned.

Wear, 2009

Wear testing equipment and tests used in research laboratories are often miniature or simplified ... more Wear testing equipment and tests used in research laboratories are often miniature or simplified versions of real applications. For example standardized ASTM dry sand rubber wheel abrasion test G 65 and pin abrasion test G 132 are widely used to study materials' abrasion wear resistance. The test results, however, do not always correlate too well with the results obtained from real wear conditions. One reason for this is, for example, that in the crushing applications of mining industry the abrasive size is usually much larger than that used in the laboratory wear tests. To study the abrasive wear caused by larger size gravel, new three-body abrasion test equipment was therefore constructed. The equipment uses the pin-on-disk principle with free abrasive particles of sizes up to 10 mm. During the test the pin is repeatedly pressed against a fixed amount of abrasive that is rotating with the disk having confining walls. As the pin is prevented from touching the counterbody, only the abrasive acts as the wearing agent. Three steels of different hardnesses were cross-tested as pin-disk pairs and as pins against a rubber disk using three igneous rock gravels with different crushability properties as abrasives. The wear was measured as mass loss from both the pin and the disk, and the rock comminution was measured by sieving. The results indicate that the mechanism of wear is greatly affected by the hardness of the counterbody. When using large size abrasives, the rate of comminution is also a very important factor that can significantly affect the wear test results.

Materials Science and Engineering: A, 2003

A variety of experimental techniques have been used to investigate the interactions between tungs... more A variety of experimental techniques have been used to investigate the interactions between tungsten carbide (WC–Co 88/12) particulates and the matrix in some new wear resistant cobalt-based superalloy and steel matrix composites produced by hot isostatic pressing. The results show that the chemical composition of the matrix has a strong influence on the interface reaction between WC and matrix and

Joint Nordic Conference on Powder Technology, 1996