Kati Valtonen | Tampere University (original) (raw)
Papers by Kati Valtonen
Wear, 2013
ABSTRACT Understanding how the wear environment and the history of the wear surfaces affect wear ... more ABSTRACT Understanding how the wear environment and the history of the wear surfaces affect wear and wear rates is extremely important in mineral processing and mining applications. Through this, the lifetime expectations of wear parts can be estimated more precisely in wear environments with constantly changing abrasive media. Certain mineral combinations can increase wear rates extensively compared to some others. The economical effects of unnecessary down-times are significant. In this study, the effects of embedded quartz layer on wear rates were investigated. Hard metals, metal matrix composites, and several types of steels were studied to find differences in their wear behavior. Running-in of the specimens was performed using quartz or granite abrasives to create surfaces with and without embedded quartz. Only granite was used as an abrasive in the actual wear tests. For low-hardness materials (<400 HV), the quartz running-in increased the wear rates in the actual wear tests, whereas for medium-hardness materials (400–800 HV) the wear rates were decreased. When the hardness of the tested material was higher than the hardness of quartz, the selection of running-in abrasive did not have an effect on the further wear rate. Characteristics of the embedded quartz layers on different substrates were further determined by scanning electron microscopy.
Nordic Pulp and Paper Research Journal, 2000
Tribology Materials Surfaces Interfaces, Feb 10, 2014
Proceedings of Nordtrib 2010, 14th Nordic Symposium on Tribology, Storforsen, Sweden 8.-11.6.2010... more Proceedings of Nordtrib 2010, 14th Nordic Symposium on Tribology, Storforsen, Sweden 8.-11.6.2010 A set of thermal sprayed and laser cladded WC- metal matrix thick coatings were studied by scratch testing to address the cracking behaviour. Failure mechanisms at different loadings have strong dependency on microstructure and stresses applied by rigid indenter sliding on the coating. Scratch tracks were studied by optical microscope and generated cracks were studied by SEM. In thermal sprayed coatings collapsing of material, formation of angular cracks, semi-circular cracks and delamination of material were observed. For laser cladded coatings due to higher binder content, plastic deformation of binder was dominant failure mechanism. Additionally, cracking of big carbides, carbide-binder interface cracking and limited binder fracture were observed.
Appita Journal
Results obtained with new water-based barrier coatings for paper and paperboard are presented. Th... more Results obtained with new water-based barrier coatings for paper and paperboard are presented. These coatings include polyester-based coatings, dispersions containing hydrophobic monomers and coatings made from biodegradable polymers. Coatings were tested as such, some were filled with talc and some were used as an additive in a commercial polymer dispersion. Relatively good barrier values were achieved. However, work needs to be done to optimise the properties of biodegradable polymers for water-based coatings. The object of this study was also to compare different fillers and additives in water-based barrier coatings. The coating performance can be controlled by a suitable choice of fillers. Folding of filled coatings destroys the barrier due to pinholes and cracks. Certain additives can improve the barrier performance of the coatings; however, filler type and filler addition level are often the dominating factors as far as barrier properties are concerned.
Earth moving machinery has to withstand heavy wear caused by loading and unloading of soil into b... more Earth moving machinery has to withstand heavy wear caused by loading and unloading of soil into buckets and tipper bodies. Especially the edge parts are subjected to heavy wear. To simulate these conditions, impeller-tumbler impact-abrasion wear testing equipment was used to determine the wear resistance of four steel grades at two sample angles. Natural granite rock was used as abrasive. The wear rates were clearly lower for the harder materials. The significance of hardness was quite similar at both test angles in the steady-state wear of wear resistant steels. On the initial wear rate, hardness had a greater effect at the larger angle due to more severe wear in sample edges already at the beginning of the test. Overall, the largest differences in wear were observed in the sample edges. At the larger test angle, the sample edges were much more rounded. Some differences were observed in the surface formations due to dissimilar movement of the abrasive. Deformed surfaces and fractur...
Understanding the effect of testing parameters is important for getting the test environment as c... more Understanding the effect of testing parameters is important for getting the test environment as close as possible to real applications and for understanding the processes that are involved in the testing itself. A pin mill type slurry-pot wear tester was developed for heavy-duty testing with high speed and large abrasive size. This study focuses on the effect of different testing parameters on large particle slurry testing. Parameters such as rotation speed of the samples, particle size and slurry concentration were varied. Round steel samples and slurry with water and granite gravel were used for testing. The test parameter variations were 4 to 10 mm for granite particle size, up to 23 wt% for slurry concentration and up to 20 m/s for sample tip speed. The relationship between the particle size, slurry concentration, and the amount of particles are discussed. Also the role of the kinetic energy of the abrasive particles is considered for large particle sizes.
A high speed slurry-pot type erosion wear tester was developed for testing of wear resistant mate... more A high speed slurry-pot type erosion wear tester was developed for testing of wear resistant materials for industrial applications. In the tester, the samples are attached to a vertical rotating shaft on four levels in a pin mill configuration. High speeds at the sample tip, up to 20 m/s, can be achieved also with large abrasive size up to 10 mm. In the tests, the equipment proved to be functional and durable even with the high loads created by the high speeds and large abrasive sizes. There are, however, large variations in the slurry concentrations and thereby wear rates at the different sample levels. In the tests with fixed sample levels, this leads to considerable uncertainties and variations in the test results. Therefore, another test method with sample rotation was developed. By rotating the samples evenly through all sample levels, the overall deviations between samples could be minimized. With the sample rotation method, up to eight materials can be tested simultaneously. ...
Uniaxial Crusher is non-standardized wear testing device located in Tampere Wear Center. It is de... more Uniaxial Crusher is non-standardized wear testing device located in Tampere Wear Center. It is designed for evaluating wear resistance in compressive crushing performance. In this study various wear resistant materials have been tested and their wear surfaces characterized with scanning electron microscopy. Besides testing materials, the key was also to evaluate how suitable the device is for wear testing. Abrasive wear was the most common wear mechanism founded in studied surfaces. Also marks of fatigue were seen. The material lost was mostly due to plastic deformation. Higher hardness indicates better wear resistance especially in cases where wear is purely abrasive.
Glass fibre reinforced vinyl ester composites are widely used in tanks, piping, ducts, and fans i... more Glass fibre reinforced vinyl ester composites are widely used in tanks, piping, ducts, and fans in demanding applications, such as waste water treatment plants, chemical processing, and pulp and paper manufacturing due to their excellent chemical resistance and mechanical performance. In addition to corrosive environments, materials are typically exposed to erosion wear and high temperatures (close to 100°C) in many hydrometallurgical processes. However, there is limited understanding on the erosion wear of vinyl ester based composites and, therefore, knowledge should be gained on this field in order to evaluate their long-term behaviour and to optimise the maintenance intervals of different structures in various wear conditions. This study evaluates the slurry-erosion wear of glass fibre reinforced vinyl ester composites (VE-FRP) using a high speed slurry-pot type wear tester. The wear rates of VE-FRP were compared using different abrasives, namely quartz, chromite, ore, concentrat...
One of the testing methods used to simulate slurry erosion in laboratory conditions is the slurry... more One of the testing methods used to simulate slurry erosion in laboratory conditions is the slurry-pot method. In this work, a novel high speed slurry-pot type erosion wear tester was constructed for testing of materials used in mining and other mineral handling applications. In the tester, the samples are attached to a vertical rotating shaft on four levels in a pin mill configuration. High speeds up to 20 m/s at the sample tip can be achieved also with large abrasive size up to 10 mm. In the tests, the equipment proved to be functional and durable even with the high loads created by the high speeds and large abrasive sizes. There are, however, variations in the slurry concentrations inside the pot during testing, leading to different wear rates at the different sample levels. Therefore, a sample rotation test method was developed. By rotating the samples evenly through all sample levels, the overall deviations between samples will be minimized. Furthermore, with the sample rotation...
Wear, 2015
ABSTRACT High strength steels (HSS) used in highly abrasive environments, such as in mining and c... more ABSTRACT High strength steels (HSS) used in highly abrasive environments, such as in mining and crushing, must endure high stress abrasion. To properly understand the wear behavior of materials under such circumstances, the connection between surface loading, work hardening, and material removal has first to be determined. In this study, wear resistant steels with initial hardness ranging from 400 to 750 HV were investigated in single-grit abrasion. In the cyclic abrasion experiments, the abrasion resistance of the steels was improved noticeably from the initial state due to surface hardening. However, the highest surface hardening rate did not result in the highest wear resistance. Moreover, when the surface loading was sufficiently increased, the transition to a high wear rate mechanism was observed.
Tribology - Materials Surfaces & Interfaces
Wear, 2013
ABSTRACT Understanding how the wear environment and the history of the wear surfaces affect wear ... more ABSTRACT Understanding how the wear environment and the history of the wear surfaces affect wear and wear rates is extremely important in mineral processing and mining applications. Through this, the lifetime expectations of wear parts can be estimated more precisely in wear environments with constantly changing abrasive media. Certain mineral combinations can increase wear rates extensively compared to some others. The economical effects of unnecessary down-times are significant. In this study, the effects of embedded quartz layer on wear rates were investigated. Hard metals, metal matrix composites, and several types of steels were studied to find differences in their wear behavior. Running-in of the specimens was performed using quartz or granite abrasives to create surfaces with and without embedded quartz. Only granite was used as an abrasive in the actual wear tests. For low-hardness materials (<400 HV), the quartz running-in increased the wear rates in the actual wear tests, whereas for medium-hardness materials (400–800 HV) the wear rates were decreased. When the hardness of the tested material was higher than the hardness of quartz, the selection of running-in abrasive did not have an effect on the further wear rate. Characteristics of the embedded quartz layers on different substrates were further determined by scanning electron microscopy.
Nordic Pulp and Paper Research Journal, 2000
Tribology Materials Surfaces Interfaces, Feb 10, 2014
Proceedings of Nordtrib 2010, 14th Nordic Symposium on Tribology, Storforsen, Sweden 8.-11.6.2010... more Proceedings of Nordtrib 2010, 14th Nordic Symposium on Tribology, Storforsen, Sweden 8.-11.6.2010 A set of thermal sprayed and laser cladded WC- metal matrix thick coatings were studied by scratch testing to address the cracking behaviour. Failure mechanisms at different loadings have strong dependency on microstructure and stresses applied by rigid indenter sliding on the coating. Scratch tracks were studied by optical microscope and generated cracks were studied by SEM. In thermal sprayed coatings collapsing of material, formation of angular cracks, semi-circular cracks and delamination of material were observed. For laser cladded coatings due to higher binder content, plastic deformation of binder was dominant failure mechanism. Additionally, cracking of big carbides, carbide-binder interface cracking and limited binder fracture were observed.
Appita Journal
Results obtained with new water-based barrier coatings for paper and paperboard are presented. Th... more Results obtained with new water-based barrier coatings for paper and paperboard are presented. These coatings include polyester-based coatings, dispersions containing hydrophobic monomers and coatings made from biodegradable polymers. Coatings were tested as such, some were filled with talc and some were used as an additive in a commercial polymer dispersion. Relatively good barrier values were achieved. However, work needs to be done to optimise the properties of biodegradable polymers for water-based coatings. The object of this study was also to compare different fillers and additives in water-based barrier coatings. The coating performance can be controlled by a suitable choice of fillers. Folding of filled coatings destroys the barrier due to pinholes and cracks. Certain additives can improve the barrier performance of the coatings; however, filler type and filler addition level are often the dominating factors as far as barrier properties are concerned.
Earth moving machinery has to withstand heavy wear caused by loading and unloading of soil into b... more Earth moving machinery has to withstand heavy wear caused by loading and unloading of soil into buckets and tipper bodies. Especially the edge parts are subjected to heavy wear. To simulate these conditions, impeller-tumbler impact-abrasion wear testing equipment was used to determine the wear resistance of four steel grades at two sample angles. Natural granite rock was used as abrasive. The wear rates were clearly lower for the harder materials. The significance of hardness was quite similar at both test angles in the steady-state wear of wear resistant steels. On the initial wear rate, hardness had a greater effect at the larger angle due to more severe wear in sample edges already at the beginning of the test. Overall, the largest differences in wear were observed in the sample edges. At the larger test angle, the sample edges were much more rounded. Some differences were observed in the surface formations due to dissimilar movement of the abrasive. Deformed surfaces and fractur...
Understanding the effect of testing parameters is important for getting the test environment as c... more Understanding the effect of testing parameters is important for getting the test environment as close as possible to real applications and for understanding the processes that are involved in the testing itself. A pin mill type slurry-pot wear tester was developed for heavy-duty testing with high speed and large abrasive size. This study focuses on the effect of different testing parameters on large particle slurry testing. Parameters such as rotation speed of the samples, particle size and slurry concentration were varied. Round steel samples and slurry with water and granite gravel were used for testing. The test parameter variations were 4 to 10 mm for granite particle size, up to 23 wt% for slurry concentration and up to 20 m/s for sample tip speed. The relationship between the particle size, slurry concentration, and the amount of particles are discussed. Also the role of the kinetic energy of the abrasive particles is considered for large particle sizes.
A high speed slurry-pot type erosion wear tester was developed for testing of wear resistant mate... more A high speed slurry-pot type erosion wear tester was developed for testing of wear resistant materials for industrial applications. In the tester, the samples are attached to a vertical rotating shaft on four levels in a pin mill configuration. High speeds at the sample tip, up to 20 m/s, can be achieved also with large abrasive size up to 10 mm. In the tests, the equipment proved to be functional and durable even with the high loads created by the high speeds and large abrasive sizes. There are, however, large variations in the slurry concentrations and thereby wear rates at the different sample levels. In the tests with fixed sample levels, this leads to considerable uncertainties and variations in the test results. Therefore, another test method with sample rotation was developed. By rotating the samples evenly through all sample levels, the overall deviations between samples could be minimized. With the sample rotation method, up to eight materials can be tested simultaneously. ...
Uniaxial Crusher is non-standardized wear testing device located in Tampere Wear Center. It is de... more Uniaxial Crusher is non-standardized wear testing device located in Tampere Wear Center. It is designed for evaluating wear resistance in compressive crushing performance. In this study various wear resistant materials have been tested and their wear surfaces characterized with scanning electron microscopy. Besides testing materials, the key was also to evaluate how suitable the device is for wear testing. Abrasive wear was the most common wear mechanism founded in studied surfaces. Also marks of fatigue were seen. The material lost was mostly due to plastic deformation. Higher hardness indicates better wear resistance especially in cases where wear is purely abrasive.
Glass fibre reinforced vinyl ester composites are widely used in tanks, piping, ducts, and fans i... more Glass fibre reinforced vinyl ester composites are widely used in tanks, piping, ducts, and fans in demanding applications, such as waste water treatment plants, chemical processing, and pulp and paper manufacturing due to their excellent chemical resistance and mechanical performance. In addition to corrosive environments, materials are typically exposed to erosion wear and high temperatures (close to 100°C) in many hydrometallurgical processes. However, there is limited understanding on the erosion wear of vinyl ester based composites and, therefore, knowledge should be gained on this field in order to evaluate their long-term behaviour and to optimise the maintenance intervals of different structures in various wear conditions. This study evaluates the slurry-erosion wear of glass fibre reinforced vinyl ester composites (VE-FRP) using a high speed slurry-pot type wear tester. The wear rates of VE-FRP were compared using different abrasives, namely quartz, chromite, ore, concentrat...
One of the testing methods used to simulate slurry erosion in laboratory conditions is the slurry... more One of the testing methods used to simulate slurry erosion in laboratory conditions is the slurry-pot method. In this work, a novel high speed slurry-pot type erosion wear tester was constructed for testing of materials used in mining and other mineral handling applications. In the tester, the samples are attached to a vertical rotating shaft on four levels in a pin mill configuration. High speeds up to 20 m/s at the sample tip can be achieved also with large abrasive size up to 10 mm. In the tests, the equipment proved to be functional and durable even with the high loads created by the high speeds and large abrasive sizes. There are, however, variations in the slurry concentrations inside the pot during testing, leading to different wear rates at the different sample levels. Therefore, a sample rotation test method was developed. By rotating the samples evenly through all sample levels, the overall deviations between samples will be minimized. Furthermore, with the sample rotation...
Wear, 2015
ABSTRACT High strength steels (HSS) used in highly abrasive environments, such as in mining and c... more ABSTRACT High strength steels (HSS) used in highly abrasive environments, such as in mining and crushing, must endure high stress abrasion. To properly understand the wear behavior of materials under such circumstances, the connection between surface loading, work hardening, and material removal has first to be determined. In this study, wear resistant steels with initial hardness ranging from 400 to 750 HV were investigated in single-grit abrasion. In the cyclic abrasion experiments, the abrasion resistance of the steels was improved noticeably from the initial state due to surface hardening. However, the highest surface hardening rate did not result in the highest wear resistance. Moreover, when the surface loading was sufficiently increased, the transition to a high wear rate mechanism was observed.
Tribology - Materials Surfaces & Interfaces