The dry sliding wear behaviour of two HVOF-sprayed Fe-Cr-Ni-Si-B-C (Colferoloy) alloy coatings wa... more The dry sliding wear behaviour of two HVOF-sprayed Fe-Cr-Ni-Si-B-C (Colferoloy) alloy coatings was studied by ball-on-disk tests performed at room temperature (against alumina and 100Cr6 steel balls), at 400 °C and at 700 °C (against alumina balls only). HVOF-sprayed Ni-Cr-Fe-B-Si-C and Cr3C2-NiCr layers were also tested for comparison. Under all test conditions, the wear rate of the Colferoloy coatings is lower than that of the Ni-Cr-Fe-B-Si-C coating but larger than that of the Cr3C2-NiCr cermet. Specifically, at room temperature, the Colferoloy coatings exhibit a combination of mild abrasion, delamination and tribo-oxidative wear against alumina, whereas, against steel, they undergo very limited delamination with negligible wear loss. By contrast, the Ni-Cr-Fe-B-Si-C coating suffers larger wear against steel and undergoes more severe abrasive grooving against alumina. Although the Colferoloy and Ni- Cr-Fe-B-Si-C coatings possess similar microstructure and micro-hardness, their sc...
This paper describes the production of self-lubricating chromium carbide-nickel coatings using th... more This paper describes the production of self-lubricating chromium carbide-nickel coatings using the HVOF spraying process. The present work deals with the preparation of Cr3C2-Ni + CaF2 multicomponent powders and to spray them with a minimum loss of the CaF2 solid lubricating phase. The powders are processed by atomization with subsequent sintering and qualification processes. The microstructure of the powder and resulting layers is characterized by SEM. The content of calcium fluoride in the sprayed layer is determined using the EDS method and compared with its content in the spray powder. Wear resistance is measured using a rubber wheel tester. Paper includes a German-language abstract.
The main focus of this study is sealed zirconia-based thermal barrier coatings produced by plasma... more The main focus of this study is sealed zirconia-based thermal barrier coatings produced by plasma spraying. AEM examinations conducted on phosphate-sealed Y2O3-ZrO2 coatings and orthophosphoric acid sealed MgO-ZrO2 coatings provide detailed information on the phases in the sealed coatings and the bonding mechanism of phosphate-based sealants on zirconia. In the case of aluminum phosphate sealed alumina and chromia, the primary objective is to add clarity on the bonding mechanism by means of transmission electron microscopy. Investigations of the sealing-layer interface indicate that the sealing of the layer lamellas is due to chemical reactions. Paper includes a German-language abstract.
Thermal Spray 2005: Proceedings from the International Thermal Spray Conference
Laser cladding is a surface treatment technology in which thick, dense and metallurgically adhere... more Laser cladding is a surface treatment technology in which thick, dense and metallurgically adhered metallic layers are deposited on various structural steels with relatively low heat input, high accuracy and reproducibility. Laser cladding processes used in industrial cladding are largely based on the use of CO2 or Nd:YAG lasers. High power diode lasers (HPDL) with rectangular beam spots are regarded as ideal laser sources for laser cladding processes, due to their compact size, high electrical to optical efficiency, easy operation, and low investment and running costs. In laser cladding of large surface areas, the affectivity of the laser cladding process becomes more important, i.e. high laser powers, wide laser beam spots, and high coating material feedrates are regarded as beneficial. In order to optimise the cladding process for such applications, special attention has to be put on devices used to deliver the coating power to the process. In the present work, various parameters...
This paper provides a short summary of the information that can be found in the literature on the... more This paper provides a short summary of the information that can be found in the literature on the preparation and structure of titanium carbide (TiC) wettable powders. From the work that has been done, it can be concluded that TiC-based coatings can be tailored for applications where complex stress profiles are encountered. Paper includes a German-language abstract.
Thermal Spray 1998: Proceedings from the International Thermal Spray Conference
Several recently published studies have shown remarkable improvements in dry abrasion resistance ... more Several recently published studies have shown remarkable improvements in dry abrasion resistance and corrosion resistance of aluminum phosphate sealed oxide coatings when compared to unsealed ones. There are numerous applications in chemical industry where a corrosive environment is accompanied with abrasive or erosive particles. In this study the wet abrasion resistance and slurry erosion resistance of aluminum phosphate-sealed and unsealed oxide coatings were studied and compared to their dry abrasion resistance. In wet abrasion tests kaolin and water mixture was used as the abrasive. In slurry erosion tests several abrasives in water with various pH values was used as the erosive medium. The coatings were characterized for microstructure and their wear mechanisms were analyzed using SEM. The results from wear tests are reported and correlated with coating properties. The influence of coating quality to the relative improvement achieved by sealing is presented and discussed.
International Congress on Applications of Lasers & Electro-Optics, 2005
Laser coating (laser cladding) is a novel way to produce metal matrix composite (MMC) coatings. T... more Laser coating (laser cladding) is a novel way to produce metal matrix composite (MMC) coatings. The selection of the metallic matrix can be done on the base of the intended application and environment, whereas the additional wear resistance improvement is provided by mixing various carbides with the metallic matrix. In the present work, various types of MMC coatings were prepared by laser coating methods. The coatings consisted of VC, WC, TiC and CrC hard phases mixed with metallic tool steel M2, Stellite 21, NiCrBSi-alloy and Inconel 625. Different levels of carbide contents were used. The abrasion resistances of the MMC coatings were tested using a rubber wheel abrasion apparatus. The wear surfaces were examined and the microstructures of MMC coatings were analysed in order to determine microstructures and carbide dissolution. The best results abrasion results were achieved by right choice of carbide to each matrix material.Laser coating (laser cladding) is a novel way to produce metal matrix composite (MMC) coatings. The selection of the metallic matrix can be done on the base of the intended application and environment, whereas the additional wear resistance improvement is provided by mixing various carbides with the metallic matrix. In the present work, various types of MMC coatings were prepared by laser coating methods. The coatings consisted of VC, WC, TiC and CrC hard phases mixed with metallic tool steel M2, Stellite 21, NiCrBSi-alloy and Inconel 625. Different levels of carbide contents were used. The abrasion resistances of the MMC coatings were tested using a rubber wheel abrasion apparatus. The wear surfaces were examined and the microstructures of MMC coatings were analysed in order to determine microstructures and carbide dissolution. The best results abrasion results were achieved by right choice of carbide to each matrix material.
Structure and wear properties of atmospheric plasma sprayed and detonation gun sprayed coatings p... more Structure and wear properties of atmospheric plasma sprayed and detonation gun sprayed coatings prepared from an experimental (Ti,Mo)C-28.4%NiCo powder were compared to coatings sprayed from commercially available WC-12%Co and Cr{sub 3}C{sub 2}-25%NiCr powders. All powders had an agglomerated (spray dried) and sintered structure and nearly the same content of the metallic binder of approximately 20 vol.-%. The powders were characterized by SEM (morphology and cross-sections) and X-ray diffraction (phase composition). The coatings were studied by optical microscope, microhardness measurements, X-ray diffraction analysis and by abrasion and erosion wear tests. The X-ray diffraction patterns of the coatings show that the (Ti,Mo)C-28.4%NiCo powder is characterized by high phase stability in both spray processes, whereas the WC-12%Co powder is prone to significant phase transformations during spraying. The results clearly show the high potential of the experimental (Ti,Mo)C-28.4%NiCo coa...
Thermal spraying includes a group of coating processes in which metallic and nonmetallic material... more Thermal spraying includes a group of coating processes in which metallic and nonmetallic materials are spray deposited as fine particles in a molten or semimolten condition or even in fully solid state to form a coating. Thermal spraying allows deposition of coatings, from some tens of micrometers up to several millimeters in thickness. Thermally sprayed coatings are used in very different applications including protective and functional coatings in mechanical engineering, energy technology, biomedical, steel, automotive, aerospace, and many other industrial sectors. The present overview is a generic summary of the topic trying to comprehensively cover many important related aspects and to give to the reader a general knowledge about the technology, formation of the coatings, coating materials with their properties, and industrial applications of the coatings.
Thermal Spray 1998: Proceedings from the International Thermal Spray Conference, 1998
Oxide-bonded silicon nitride (OBSN) powders have been developed to address thermal spray problems... more Oxide-bonded silicon nitride (OBSN) powders have been developed to address thermal spray problems associated with high temperatures. This paper examines how such powders perform when applied via detonation gun (DGS) and atmospheric plasma spraying (APS) with axial powder injection. All coatings were characterized using optical microscopy and X-ray diffraction with additional tests being performed on DGS coatings. For the first time, relatively dense Si3N4-rich coatings with an oxide binder phase were produced, and some of the DGS coatings were found to be sufficiently wear resistance for industrial use.
HVOF spraying is used to produce NiCoCrAlYRe deposits that serve as adhesive layers for plasma-sp... more HVOF spraying is used to produce NiCoCrAlYRe deposits that serve as adhesive layers for plasma-sprayed thermal barrier coatings. This paper investigates the influence of HVOF spray parameters on the structure and properties of the adhesion-promoting layers. Spray parameters are optimized to produce high layer densities with low degrees of oxidation and a surface roughness comparable to that of the thermal barrier coatings. A vacuum-sprayed layer with similar composition is also examined. Following the application of the TBC, the oxidized layers are characterized based on microstructure, oxide layer thickness, proportion of the NiAl phase, and imperfections at the boundary layer. It is observed that the less expensive HVOF layer offers the same protective properties as a vacuum plasma sprayed bond coat. Paper includes a German-language abstract.
Hot corrosion tests have been conducted on Ni- and Cr-based laser coatings, a high-velocity oxy-f... more Hot corrosion tests have been conducted on Ni- and Cr-based laser coatings, a high-velocity oxy-fuel (HVOF) sprayed coating and various wrought alloys covered with a synthetic salt of Na2SO4-V2O5 and exposed at 650°C for 1000 h in air. Coating microstructures and reaction product layers were analyzed with scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The hot corrosion resistance of tested specimen was evaluated by measuring its mean thickness loss. Generally, wrought alloys, HVOF coating and Cr-based laser coatings suffered from selective corrosion beneath salt film, that is, distinct Cr-depleted layer was formed at alloy/salt interface. Cr-based laser coatings exhibited extended solid solubility and they transformed towards equilibrium condition. Cr-rich phases enriched further with Cr and they were prone to corrosion. Low diluted laser coatings and HVOF coating were more resistant to hot corrosion than commonly used industrial standard alloy, Nimonic...
Thermal Spray 2005: Proceedings from the International Thermal Spray Conference
The paper describes the some differences of laser coating (laser cladding or laser spraying) proc... more The paper describes the some differences of laser coating (laser cladding or laser spraying) process in comparison to thermal spraying. Laser coating is a novel coating process, which produces coatings with high density, metallurgical bonding and low heat input to the substrate. Laser coating types and coating properties are reviewed and compared with thermally sprayed coatings. Typical application areas of laser coatings are presented.
The dry sliding wear behaviour of two HVOF-sprayed Fe-Cr-Ni-Si-B-C (Colferoloy) alloy coatings wa... more The dry sliding wear behaviour of two HVOF-sprayed Fe-Cr-Ni-Si-B-C (Colferoloy) alloy coatings was studied by ball-on-disk tests performed at room temperature (against alumina and 100Cr6 steel balls), at 400 °C and at 700 °C (against alumina balls only). HVOF-sprayed Ni-Cr-Fe-B-Si-C and Cr3C2-NiCr layers were also tested for comparison. Under all test conditions, the wear rate of the Colferoloy coatings is lower than that of the Ni-Cr-Fe-B-Si-C coating but larger than that of the Cr3C2-NiCr cermet. Specifically, at room temperature, the Colferoloy coatings exhibit a combination of mild abrasion, delamination and tribo-oxidative wear against alumina, whereas, against steel, they undergo very limited delamination with negligible wear loss. By contrast, the Ni-Cr-Fe-B-Si-C coating suffers larger wear against steel and undergoes more severe abrasive grooving against alumina. Although the Colferoloy and Ni- Cr-Fe-B-Si-C coatings possess similar microstructure and micro-hardness, their sc...
This paper describes the production of self-lubricating chromium carbide-nickel coatings using th... more This paper describes the production of self-lubricating chromium carbide-nickel coatings using the HVOF spraying process. The present work deals with the preparation of Cr3C2-Ni + CaF2 multicomponent powders and to spray them with a minimum loss of the CaF2 solid lubricating phase. The powders are processed by atomization with subsequent sintering and qualification processes. The microstructure of the powder and resulting layers is characterized by SEM. The content of calcium fluoride in the sprayed layer is determined using the EDS method and compared with its content in the spray powder. Wear resistance is measured using a rubber wheel tester. Paper includes a German-language abstract.
The main focus of this study is sealed zirconia-based thermal barrier coatings produced by plasma... more The main focus of this study is sealed zirconia-based thermal barrier coatings produced by plasma spraying. AEM examinations conducted on phosphate-sealed Y2O3-ZrO2 coatings and orthophosphoric acid sealed MgO-ZrO2 coatings provide detailed information on the phases in the sealed coatings and the bonding mechanism of phosphate-based sealants on zirconia. In the case of aluminum phosphate sealed alumina and chromia, the primary objective is to add clarity on the bonding mechanism by means of transmission electron microscopy. Investigations of the sealing-layer interface indicate that the sealing of the layer lamellas is due to chemical reactions. Paper includes a German-language abstract.
Thermal Spray 2005: Proceedings from the International Thermal Spray Conference
Laser cladding is a surface treatment technology in which thick, dense and metallurgically adhere... more Laser cladding is a surface treatment technology in which thick, dense and metallurgically adhered metallic layers are deposited on various structural steels with relatively low heat input, high accuracy and reproducibility. Laser cladding processes used in industrial cladding are largely based on the use of CO2 or Nd:YAG lasers. High power diode lasers (HPDL) with rectangular beam spots are regarded as ideal laser sources for laser cladding processes, due to their compact size, high electrical to optical efficiency, easy operation, and low investment and running costs. In laser cladding of large surface areas, the affectivity of the laser cladding process becomes more important, i.e. high laser powers, wide laser beam spots, and high coating material feedrates are regarded as beneficial. In order to optimise the cladding process for such applications, special attention has to be put on devices used to deliver the coating power to the process. In the present work, various parameters...
This paper provides a short summary of the information that can be found in the literature on the... more This paper provides a short summary of the information that can be found in the literature on the preparation and structure of titanium carbide (TiC) wettable powders. From the work that has been done, it can be concluded that TiC-based coatings can be tailored for applications where complex stress profiles are encountered. Paper includes a German-language abstract.
Thermal Spray 1998: Proceedings from the International Thermal Spray Conference
Several recently published studies have shown remarkable improvements in dry abrasion resistance ... more Several recently published studies have shown remarkable improvements in dry abrasion resistance and corrosion resistance of aluminum phosphate sealed oxide coatings when compared to unsealed ones. There are numerous applications in chemical industry where a corrosive environment is accompanied with abrasive or erosive particles. In this study the wet abrasion resistance and slurry erosion resistance of aluminum phosphate-sealed and unsealed oxide coatings were studied and compared to their dry abrasion resistance. In wet abrasion tests kaolin and water mixture was used as the abrasive. In slurry erosion tests several abrasives in water with various pH values was used as the erosive medium. The coatings were characterized for microstructure and their wear mechanisms were analyzed using SEM. The results from wear tests are reported and correlated with coating properties. The influence of coating quality to the relative improvement achieved by sealing is presented and discussed.
International Congress on Applications of Lasers & Electro-Optics, 2005
Laser coating (laser cladding) is a novel way to produce metal matrix composite (MMC) coatings. T... more Laser coating (laser cladding) is a novel way to produce metal matrix composite (MMC) coatings. The selection of the metallic matrix can be done on the base of the intended application and environment, whereas the additional wear resistance improvement is provided by mixing various carbides with the metallic matrix. In the present work, various types of MMC coatings were prepared by laser coating methods. The coatings consisted of VC, WC, TiC and CrC hard phases mixed with metallic tool steel M2, Stellite 21, NiCrBSi-alloy and Inconel 625. Different levels of carbide contents were used. The abrasion resistances of the MMC coatings were tested using a rubber wheel abrasion apparatus. The wear surfaces were examined and the microstructures of MMC coatings were analysed in order to determine microstructures and carbide dissolution. The best results abrasion results were achieved by right choice of carbide to each matrix material.Laser coating (laser cladding) is a novel way to produce metal matrix composite (MMC) coatings. The selection of the metallic matrix can be done on the base of the intended application and environment, whereas the additional wear resistance improvement is provided by mixing various carbides with the metallic matrix. In the present work, various types of MMC coatings were prepared by laser coating methods. The coatings consisted of VC, WC, TiC and CrC hard phases mixed with metallic tool steel M2, Stellite 21, NiCrBSi-alloy and Inconel 625. Different levels of carbide contents were used. The abrasion resistances of the MMC coatings were tested using a rubber wheel abrasion apparatus. The wear surfaces were examined and the microstructures of MMC coatings were analysed in order to determine microstructures and carbide dissolution. The best results abrasion results were achieved by right choice of carbide to each matrix material.
Structure and wear properties of atmospheric plasma sprayed and detonation gun sprayed coatings p... more Structure and wear properties of atmospheric plasma sprayed and detonation gun sprayed coatings prepared from an experimental (Ti,Mo)C-28.4%NiCo powder were compared to coatings sprayed from commercially available WC-12%Co and Cr{sub 3}C{sub 2}-25%NiCr powders. All powders had an agglomerated (spray dried) and sintered structure and nearly the same content of the metallic binder of approximately 20 vol.-%. The powders were characterized by SEM (morphology and cross-sections) and X-ray diffraction (phase composition). The coatings were studied by optical microscope, microhardness measurements, X-ray diffraction analysis and by abrasion and erosion wear tests. The X-ray diffraction patterns of the coatings show that the (Ti,Mo)C-28.4%NiCo powder is characterized by high phase stability in both spray processes, whereas the WC-12%Co powder is prone to significant phase transformations during spraying. The results clearly show the high potential of the experimental (Ti,Mo)C-28.4%NiCo coa...
Thermal spraying includes a group of coating processes in which metallic and nonmetallic material... more Thermal spraying includes a group of coating processes in which metallic and nonmetallic materials are spray deposited as fine particles in a molten or semimolten condition or even in fully solid state to form a coating. Thermal spraying allows deposition of coatings, from some tens of micrometers up to several millimeters in thickness. Thermally sprayed coatings are used in very different applications including protective and functional coatings in mechanical engineering, energy technology, biomedical, steel, automotive, aerospace, and many other industrial sectors. The present overview is a generic summary of the topic trying to comprehensively cover many important related aspects and to give to the reader a general knowledge about the technology, formation of the coatings, coating materials with their properties, and industrial applications of the coatings.
Thermal Spray 1998: Proceedings from the International Thermal Spray Conference, 1998
Oxide-bonded silicon nitride (OBSN) powders have been developed to address thermal spray problems... more Oxide-bonded silicon nitride (OBSN) powders have been developed to address thermal spray problems associated with high temperatures. This paper examines how such powders perform when applied via detonation gun (DGS) and atmospheric plasma spraying (APS) with axial powder injection. All coatings were characterized using optical microscopy and X-ray diffraction with additional tests being performed on DGS coatings. For the first time, relatively dense Si3N4-rich coatings with an oxide binder phase were produced, and some of the DGS coatings were found to be sufficiently wear resistance for industrial use.
HVOF spraying is used to produce NiCoCrAlYRe deposits that serve as adhesive layers for plasma-sp... more HVOF spraying is used to produce NiCoCrAlYRe deposits that serve as adhesive layers for plasma-sprayed thermal barrier coatings. This paper investigates the influence of HVOF spray parameters on the structure and properties of the adhesion-promoting layers. Spray parameters are optimized to produce high layer densities with low degrees of oxidation and a surface roughness comparable to that of the thermal barrier coatings. A vacuum-sprayed layer with similar composition is also examined. Following the application of the TBC, the oxidized layers are characterized based on microstructure, oxide layer thickness, proportion of the NiAl phase, and imperfections at the boundary layer. It is observed that the less expensive HVOF layer offers the same protective properties as a vacuum plasma sprayed bond coat. Paper includes a German-language abstract.
Hot corrosion tests have been conducted on Ni- and Cr-based laser coatings, a high-velocity oxy-f... more Hot corrosion tests have been conducted on Ni- and Cr-based laser coatings, a high-velocity oxy-fuel (HVOF) sprayed coating and various wrought alloys covered with a synthetic salt of Na2SO4-V2O5 and exposed at 650°C for 1000 h in air. Coating microstructures and reaction product layers were analyzed with scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The hot corrosion resistance of tested specimen was evaluated by measuring its mean thickness loss. Generally, wrought alloys, HVOF coating and Cr-based laser coatings suffered from selective corrosion beneath salt film, that is, distinct Cr-depleted layer was formed at alloy/salt interface. Cr-based laser coatings exhibited extended solid solubility and they transformed towards equilibrium condition. Cr-rich phases enriched further with Cr and they were prone to corrosion. Low diluted laser coatings and HVOF coating were more resistant to hot corrosion than commonly used industrial standard alloy, Nimonic...
Thermal Spray 2005: Proceedings from the International Thermal Spray Conference
The paper describes the some differences of laser coating (laser cladding or laser spraying) proc... more The paper describes the some differences of laser coating (laser cladding or laser spraying) process in comparison to thermal spraying. Laser coating is a novel coating process, which produces coatings with high density, metallurgical bonding and low heat input to the substrate. Laser coating types and coating properties are reviewed and compared with thermally sprayed coatings. Typical application areas of laser coatings are presented.
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