Niko Ojala | Tampere University (original) (raw)
Papers by Niko Ojala
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. ...
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...
The wear resistance of commercial quenched wear resistant steels is commonly categorized by their... more The wear resistance of commercial quenched wear resistant steels is commonly categorized by their Brinell hardness. The hardness grades are considered almost as standards, although they are not and there are no earlier evidence about their wear performance. In this study the differences of 15 different comercially available 400 HB grade steels were tested with natural granite gravel as abrasive material. The outcome was that the difference in abrasive wear perfomance can be more than 50 %. Nominally similar 400 HB grade quenched wear resistant steels do not perform equally under heavy abrasion wear, and hardness alone is not an accurate predictor of the steel’s wear performance. Alloying and manufacturing of the steel and thus its microstructure has a significant effect particularly on the work hardening behavior of the steel during abrasion, leading to different wear performances under such conditions.
Wear, 2014
Wear resistant steels are commonly categorized by their hardness, and in the case of quenched wea... more Wear resistant steels are commonly categorized by their hardness, and in the case of quenched wear resistant steels, their Brinell hardness grades are widely considered almost as standards. In this study, the abrasive wear performance of 15 commercially available 400 HB grade quenched wear resistant steels from all over the world were tested with granite gravel in high stress conditions. The aim was to evaluate the real wear performance of nominally similar steels. Also properties such as hardness, hardness profiles, microstructures and chemical compositions of the steels were studied and reasons for the differences in their wear performance further discussed. In terms of mass loss, over 50 percent differences were recorded in the abrasive wear performance of the studied steels. Variations in the chemical compositions were linked to the auto-tempered microstructures of the steels, and the microstructural characteristics were further linked to their ultimate wear behavior.
Tribology Materials Surfaces Interfaces, Feb 10, 2014
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. ...
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...
The wear resistance of commercial quenched wear resistant steels is commonly categorized by their... more The wear resistance of commercial quenched wear resistant steels is commonly categorized by their Brinell hardness. The hardness grades are considered almost as standards, although they are not and there are no earlier evidence about their wear performance. In this study the differences of 15 different comercially available 400 HB grade steels were tested with natural granite gravel as abrasive material. The outcome was that the difference in abrasive wear perfomance can be more than 50 %. Nominally similar 400 HB grade quenched wear resistant steels do not perform equally under heavy abrasion wear, and hardness alone is not an accurate predictor of the steel’s wear performance. Alloying and manufacturing of the steel and thus its microstructure has a significant effect particularly on the work hardening behavior of the steel during abrasion, leading to different wear performances under such conditions.
Wear, 2014
Wear resistant steels are commonly categorized by their hardness, and in the case of quenched wea... more Wear resistant steels are commonly categorized by their hardness, and in the case of quenched wear resistant steels, their Brinell hardness grades are widely considered almost as standards. In this study, the abrasive wear performance of 15 commercially available 400 HB grade quenched wear resistant steels from all over the world were tested with granite gravel in high stress conditions. The aim was to evaluate the real wear performance of nominally similar steels. Also properties such as hardness, hardness profiles, microstructures and chemical compositions of the steels were studied and reasons for the differences in their wear performance further discussed. In terms of mass loss, over 50 percent differences were recorded in the abrasive wear performance of the studied steels. Variations in the chemical compositions were linked to the auto-tempered microstructures of the steels, and the microstructural characteristics were further linked to their ultimate wear behavior.
Tribology Materials Surfaces Interfaces, Feb 10, 2014