ABSTRACT In this work the affects of laser characteristics on surface morphology, microstructure,... more ABSTRACT In this work the affects of laser characteristics on surface morphology, microstructure, microhardness and wear rates of high velocity oxygen fuel (HVOF) WC‐CoCr coatings were investigated. Continuous and pulsed laser treatments were applied on the HVOF coatings using a CO2 laser of 10.6 μm wavelength. Continuous laser treatment significantly improved homogeneity of the coatings. Pulsed laser treatment produced significantly higher discontinuities compared to continuous mode. Microhardness increased by 45% for continuous mode laser modified WC‐CoCr coatings. However, wear resistance deteriorated, with a notable 40% increase in wear rate. The variations in coating properties were attributed to the re‐melting and rapid quenching of the CoCr bonding matrix allowing for WC redistribution.
ABSTRACT High-velocity oxy-fuel (HVOF) spray techniques can produce cermet coatings for applicati... more ABSTRACT High-velocity oxy-fuel (HVOF) spray techniques can produce cermet coatings for applications that require corrosion resistant surfaces. The aim of this study was to investigate the influence of different oxygen/fuel ratios on velocity and temperature of flying particles and establish the effects on the coatings quality in relation to the corrosion behavior of HVOF WC–CoCr coating in a 0.1 N HCl. The results show that in-flight particle characteristics have a significant effect on the porosity, hardness and corrosion resistance. The highest corrosion resistance is obtained with those parameters that allow a sufficient melting of the agglomerates while minimizing the decarburization of the WC particles.
The increasing environmental pressure that in the last years has been exerted on the electrolytic... more The increasing environmental pressure that in the last years has been exerted on the electrolytic hard chromium plating technology has impelled the search of technological alternatives to these coatings. The main type of coatings that are most widely viewed as being capable of replacing hard chrome plating are the thermal spray technologies, especially high-velocity oxy-fuel (HVOF) thermal spraying, within the automotive, aeronautical and aerospace fields. The present study analyze the influence of HVOF processing parameters on the microstructure and mechanical and tribological properties of the WC-CoCr coatings, produced using two different types of fuels: liquid (kerosene) and gaseous (hydrogen). The results are compared with the conventional hard chromium plating. Microstructural analysis by optical and SEM microscopy, adherence, Micro-hardness, Roughness, Friction coefficient and Wear resistance tests have been carried out. () Centro de diseno de aleaciones Ligeras yTtratamiento...
Corrosion resistance and ion release behavior have been evaluated for thirty dental restoration s... more Corrosion resistance and ion release behavior have been evaluated for thirty dental restoration samples obtained by three different manufacturing systems: computer-aided design and manufacturing (CAD-CAM), traditional casting and laser sintering. The alloy used was the CoCr alloy (same batch) generally used in clinical dentistry. Corrosion resistance has been evaluated by electrochemical testing in an artificial saliva medium at 37 °C. Corrosion parameters such as critical current density (icr), corrosion potential (Ecorr), and passive current density (ip), have been determined. Cobalt and Chromium ions released from the different samples have also been analyzed in an artificial saliva medium at 37 °C by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) at different immersion times. The casted samples showed higher corrosion rates and ion-release levels. The CAD-CAM milled samples presented lower ion-release levels and better corrosion resistance due to the total solubility of t...
The aim of this study is to compare the mechanical properties of three different dental restorati... more The aim of this study is to compare the mechanical properties of three different dental restorations’ manufacturing processes (CADCAM milling, casting and laser sintering) generated by only one laboratory scanner focusing on marginal fit analysis and their mechanical properties. A chrome-cobalt (Cr-Co) alloy from the same batch was used for three different methods to make an implant abutment. This simulates a maxillary right first molar that was fixed in a hemi-maxillary stone model. Five scans were performed by each tested framework. Nine frameworks were manufactured for each manufacture procedure. Field-Emission Scanning Electron Microscope (FE-SEM) direct vision was used to marginal gap measurement in five critical points for each specimen. In order to fix the samples in the microscope chamber, the restorations were submitted at a compression load of 50 N. The samples always have the same orientation and conditions. The resolution of the microscope is 4 nm and it is equipped by J...
ABSTRACT High-velocity oxy-fuel (HVOF) spray techniques can produce cermet coatings for applicati... more ABSTRACT High-velocity oxy-fuel (HVOF) spray techniques can produce cermet coatings for applications that require corrosion resistant surfaces. The aim of this study was to investigate the influence of different oxygen/fuel ratios on velocity and temperature of flying particles and establish the effects on the coatings quality in relation to the corrosion behavior of HVOF WC–CoCr coating in a 0.1 N HCl. The results show that in-flight particle characteristics have a significant effect on the porosity, hardness and corrosion resistance. The highest corrosion resistance is obtained with those parameters that allow a sufficient melting of the agglomerates while minimizing the decarburization of the WC particles.
ABSTRACT High-velocity oxy-fuel (HVOF) spray techniques can produce cermet coatings for applicati... more ABSTRACT High-velocity oxy-fuel (HVOF) spray techniques can produce cermet coatings for applications that require corrosion resistant surfaces. The aim of this study was to investigate the influence of different oxygen/fuel ratios on velocity and temperature of flying particles and establish the effects on the coatings quality in relation to the corrosion behavior of HVOF WC–CoCr coating in a 0.1 N HCl. The results show that in-flight particle characteristics have a significant effect on the porosity, hardness and corrosion resistance. The highest corrosion resistance is obtained with those parameters that allow a sufficient melting of the agglomerates while minimizing the decarburization of the WC particles.
Journal of materials science. Materials in medicine, 2015
This study shows the potential risk of microfiltration between two different types of implant-abu... more This study shows the potential risk of microfiltration between two different types of implant-abutment connections screwed at 45 Ncm: external and internal. For the first time the use of a mechanical artificial mouth is used with the values (compression and torsion loads with a frequency of 2 Hz) of the human chewing. The mechanical tests were performed with an artificial saliva at 37°C. The microgap in the connection was measured by an Image Analysis software incorporated in a high resolution scanning electron microscopy. Implant connections were filled with methylene blue by using self-adjustable precision pipettes and the quantity of leakage was determined by high sensitivity spectometry. We showed that the internal connection has lower microgaps compared to the external ones and these microgaps increased with the number of mechanical cycles. The leakage of methylene blue was higher when the external connection was performed. Microgaps and the influence of the mechanical loads ar...
Journal of Materials Science: Materials in Medicine, 2015
This study shows the potential risk of microfiltration between two different types of implant-abu... more This study shows the potential risk of microfiltration between two different types of implant-abutment connections screwed at 45 Ncm: external and internal. For the first time the use of a mechanical artificial mouth is used with the values (compression and torsion loads with a frequency of 2 Hz) of the human chewing. The mechanical tests were performed with an artificial saliva at 37°C. The microgap in the connection was measured by an Image Analysis software incorporated in a high resolution scanning electron microscopy. Implant connections were filled with methylene blue by using self-adjustable precision pipettes and the quantity of leakage was determined by high sensitivity spectometry. We showed that the internal connection has lower microgaps compared to the external ones and these microgaps increased with the number of mechanical cycles. The leakage of methylene blue was higher when the external connection was performed. Microgaps and the influence of the mechanical loads are very important for the long-term behavior avoiding the bacteria colonization in the dental implants. These aspects should be known by the implantologists.
ABSTRACT Die wear is an important problem for manufacturers in hot-working processes, e.g. metal ... more ABSTRACT Die wear is an important problem for manufacturers in hot-working processes, e.g. metal die casting, hot extrusion and thixoextrusion of aluminium, magnesium or steel, as well as glass and plastics processing. The dies have to be capable of withstanding complex thermal and mechanical loads, while giving a sufficient wear resistance against abrasion and adhesion at very high temperatures. In order to improve the wear resistance and reduce the heating of the extrusion die it can be protected with a hard cermet coating. The purpose of this work is to study the high-temperature performance of Cr3C2-CoNiCrAlY coating and explore the potential application of this coating to prolong the life of tooling and dies while reducing maintenance and increasing shelf life and dimensional control. A 75Cr3C2-25CoNiCrAlY coating with a CoNiCrAlY bond coat was sprayed by HVOF thermal spray process on a steel substrate. Coatings were heat-treated at a range of temperatures between 900 °C and 1100 °C. The mechanical and tribological properties of coatings were determined as a function of the temperature of heat treatment. The bond coat effect on the thermal shock resistance of Cr3C2-CoNiCrAlY coating was analysed.
Journal of the Mechanical Behavior of Biomedical Materials, 2014
The generation of titanium foams is a promising strategy for modifying the mechanical properties ... more The generation of titanium foams is a promising strategy for modifying the mechanical properties of intervertebral reinforcements. Thus, the aim of this study was to compare the in vitro biological response of Ti6Al4V alloys with different pore sizes for use in intervertebral implants in terms of the adhesion, proliferation, and differentiation of pre-osteoblastic cells. We studied the production of Ti6Al4V foams by powder metallurgy and the biological responses to Ti6Al4V foams were assessed in terms of different pore interconnectivities and elastic moduli. The Ti6Al4V foams obtained had similar porosities of approximately 34%, but different pore sizes (66 µm for fine Ti6Al4V and 147 µm for coarse Ti6Al4V) due to the sizes of the microsphere used. The Ti6Al4V foams had a slightly higher Young׳s modulus compared with cancellous bone. The dynamic mechanical properties of the Ti6Al4V foams were slightly low, but these materials can satisfy the requirements for intervertebral prosthesis applications. The cultured cells colonized both sizes of microspheres near the pore spaces, where they occupied almost the entire area of the microspheres when the final cell culture time was reached. No statistical differences in cell proliferation were observed; however, the cells filled the pores on fine Ti6Al4V foams but they only colonized the superficial microspheres, whereas the cells did not fill the pores on coarse Ti6Al4V foams but they were distributed throughout most of the material. In addition, the microspheres with wide pores (coarse Ti6Al4V) stimulated higher osteoblast differentiation, as demonstrated by the Alcaline Phosphatase (ALP) activity. Our in vitro results suggest that foams with wide pore facilitate internal cell colonization and stimulate osteoblast differentiation.
ABSTRACT In this work the affects of laser characteristics on surface morphology, microstructure,... more ABSTRACT In this work the affects of laser characteristics on surface morphology, microstructure, microhardness and wear rates of high velocity oxygen fuel (HVOF) WC‐CoCr coatings were investigated. Continuous and pulsed laser treatments were applied on the HVOF coatings using a CO2 laser of 10.6 μm wavelength. Continuous laser treatment significantly improved homogeneity of the coatings. Pulsed laser treatment produced significantly higher discontinuities compared to continuous mode. Microhardness increased by 45% for continuous mode laser modified WC‐CoCr coatings. However, wear resistance deteriorated, with a notable 40% increase in wear rate. The variations in coating properties were attributed to the re‐melting and rapid quenching of the CoCr bonding matrix allowing for WC redistribution.
ABSTRACT High-velocity oxy-fuel (HVOF) spray techniques can produce cermet coatings for applicati... more ABSTRACT High-velocity oxy-fuel (HVOF) spray techniques can produce cermet coatings for applications that require corrosion resistant surfaces. The aim of this study was to investigate the influence of different oxygen/fuel ratios on velocity and temperature of flying particles and establish the effects on the coatings quality in relation to the corrosion behavior of HVOF WC–CoCr coating in a 0.1 N HCl. The results show that in-flight particle characteristics have a significant effect on the porosity, hardness and corrosion resistance. The highest corrosion resistance is obtained with those parameters that allow a sufficient melting of the agglomerates while minimizing the decarburization of the WC particles.
The increasing environmental pressure that in the last years has been exerted on the electrolytic... more The increasing environmental pressure that in the last years has been exerted on the electrolytic hard chromium plating technology has impelled the search of technological alternatives to these coatings. The main type of coatings that are most widely viewed as being capable of replacing hard chrome plating are the thermal spray technologies, especially high-velocity oxy-fuel (HVOF) thermal spraying, within the automotive, aeronautical and aerospace fields. The present study analyze the influence of HVOF processing parameters on the microstructure and mechanical and tribological properties of the WC-CoCr coatings, produced using two different types of fuels: liquid (kerosene) and gaseous (hydrogen). The results are compared with the conventional hard chromium plating. Microstructural analysis by optical and SEM microscopy, adherence, Micro-hardness, Roughness, Friction coefficient and Wear resistance tests have been carried out. () Centro de diseno de aleaciones Ligeras yTtratamiento...
Corrosion resistance and ion release behavior have been evaluated for thirty dental restoration s... more Corrosion resistance and ion release behavior have been evaluated for thirty dental restoration samples obtained by three different manufacturing systems: computer-aided design and manufacturing (CAD-CAM), traditional casting and laser sintering. The alloy used was the CoCr alloy (same batch) generally used in clinical dentistry. Corrosion resistance has been evaluated by electrochemical testing in an artificial saliva medium at 37 °C. Corrosion parameters such as critical current density (icr), corrosion potential (Ecorr), and passive current density (ip), have been determined. Cobalt and Chromium ions released from the different samples have also been analyzed in an artificial saliva medium at 37 °C by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) at different immersion times. The casted samples showed higher corrosion rates and ion-release levels. The CAD-CAM milled samples presented lower ion-release levels and better corrosion resistance due to the total solubility of t...
The aim of this study is to compare the mechanical properties of three different dental restorati... more The aim of this study is to compare the mechanical properties of three different dental restorations’ manufacturing processes (CADCAM milling, casting and laser sintering) generated by only one laboratory scanner focusing on marginal fit analysis and their mechanical properties. A chrome-cobalt (Cr-Co) alloy from the same batch was used for three different methods to make an implant abutment. This simulates a maxillary right first molar that was fixed in a hemi-maxillary stone model. Five scans were performed by each tested framework. Nine frameworks were manufactured for each manufacture procedure. Field-Emission Scanning Electron Microscope (FE-SEM) direct vision was used to marginal gap measurement in five critical points for each specimen. In order to fix the samples in the microscope chamber, the restorations were submitted at a compression load of 50 N. The samples always have the same orientation and conditions. The resolution of the microscope is 4 nm and it is equipped by J...
ABSTRACT High-velocity oxy-fuel (HVOF) spray techniques can produce cermet coatings for applicati... more ABSTRACT High-velocity oxy-fuel (HVOF) spray techniques can produce cermet coatings for applications that require corrosion resistant surfaces. The aim of this study was to investigate the influence of different oxygen/fuel ratios on velocity and temperature of flying particles and establish the effects on the coatings quality in relation to the corrosion behavior of HVOF WC–CoCr coating in a 0.1 N HCl. The results show that in-flight particle characteristics have a significant effect on the porosity, hardness and corrosion resistance. The highest corrosion resistance is obtained with those parameters that allow a sufficient melting of the agglomerates while minimizing the decarburization of the WC particles.
ABSTRACT High-velocity oxy-fuel (HVOF) spray techniques can produce cermet coatings for applicati... more ABSTRACT High-velocity oxy-fuel (HVOF) spray techniques can produce cermet coatings for applications that require corrosion resistant surfaces. The aim of this study was to investigate the influence of different oxygen/fuel ratios on velocity and temperature of flying particles and establish the effects on the coatings quality in relation to the corrosion behavior of HVOF WC–CoCr coating in a 0.1 N HCl. The results show that in-flight particle characteristics have a significant effect on the porosity, hardness and corrosion resistance. The highest corrosion resistance is obtained with those parameters that allow a sufficient melting of the agglomerates while minimizing the decarburization of the WC particles.
Journal of materials science. Materials in medicine, 2015
This study shows the potential risk of microfiltration between two different types of implant-abu... more This study shows the potential risk of microfiltration between two different types of implant-abutment connections screwed at 45 Ncm: external and internal. For the first time the use of a mechanical artificial mouth is used with the values (compression and torsion loads with a frequency of 2 Hz) of the human chewing. The mechanical tests were performed with an artificial saliva at 37°C. The microgap in the connection was measured by an Image Analysis software incorporated in a high resolution scanning electron microscopy. Implant connections were filled with methylene blue by using self-adjustable precision pipettes and the quantity of leakage was determined by high sensitivity spectometry. We showed that the internal connection has lower microgaps compared to the external ones and these microgaps increased with the number of mechanical cycles. The leakage of methylene blue was higher when the external connection was performed. Microgaps and the influence of the mechanical loads ar...
Journal of Materials Science: Materials in Medicine, 2015
This study shows the potential risk of microfiltration between two different types of implant-abu... more This study shows the potential risk of microfiltration between two different types of implant-abutment connections screwed at 45 Ncm: external and internal. For the first time the use of a mechanical artificial mouth is used with the values (compression and torsion loads with a frequency of 2 Hz) of the human chewing. The mechanical tests were performed with an artificial saliva at 37°C. The microgap in the connection was measured by an Image Analysis software incorporated in a high resolution scanning electron microscopy. Implant connections were filled with methylene blue by using self-adjustable precision pipettes and the quantity of leakage was determined by high sensitivity spectometry. We showed that the internal connection has lower microgaps compared to the external ones and these microgaps increased with the number of mechanical cycles. The leakage of methylene blue was higher when the external connection was performed. Microgaps and the influence of the mechanical loads are very important for the long-term behavior avoiding the bacteria colonization in the dental implants. These aspects should be known by the implantologists.
ABSTRACT Die wear is an important problem for manufacturers in hot-working processes, e.g. metal ... more ABSTRACT Die wear is an important problem for manufacturers in hot-working processes, e.g. metal die casting, hot extrusion and thixoextrusion of aluminium, magnesium or steel, as well as glass and plastics processing. The dies have to be capable of withstanding complex thermal and mechanical loads, while giving a sufficient wear resistance against abrasion and adhesion at very high temperatures. In order to improve the wear resistance and reduce the heating of the extrusion die it can be protected with a hard cermet coating. The purpose of this work is to study the high-temperature performance of Cr3C2-CoNiCrAlY coating and explore the potential application of this coating to prolong the life of tooling and dies while reducing maintenance and increasing shelf life and dimensional control. A 75Cr3C2-25CoNiCrAlY coating with a CoNiCrAlY bond coat was sprayed by HVOF thermal spray process on a steel substrate. Coatings were heat-treated at a range of temperatures between 900 °C and 1100 °C. The mechanical and tribological properties of coatings were determined as a function of the temperature of heat treatment. The bond coat effect on the thermal shock resistance of Cr3C2-CoNiCrAlY coating was analysed.
Journal of the Mechanical Behavior of Biomedical Materials, 2014
The generation of titanium foams is a promising strategy for modifying the mechanical properties ... more The generation of titanium foams is a promising strategy for modifying the mechanical properties of intervertebral reinforcements. Thus, the aim of this study was to compare the in vitro biological response of Ti6Al4V alloys with different pore sizes for use in intervertebral implants in terms of the adhesion, proliferation, and differentiation of pre-osteoblastic cells. We studied the production of Ti6Al4V foams by powder metallurgy and the biological responses to Ti6Al4V foams were assessed in terms of different pore interconnectivities and elastic moduli. The Ti6Al4V foams obtained had similar porosities of approximately 34%, but different pore sizes (66 µm for fine Ti6Al4V and 147 µm for coarse Ti6Al4V) due to the sizes of the microsphere used. The Ti6Al4V foams had a slightly higher Young׳s modulus compared with cancellous bone. The dynamic mechanical properties of the Ti6Al4V foams were slightly low, but these materials can satisfy the requirements for intervertebral prosthesis applications. The cultured cells colonized both sizes of microspheres near the pore spaces, where they occupied almost the entire area of the microspheres when the final cell culture time was reached. No statistical differences in cell proliferation were observed; however, the cells filled the pores on fine Ti6Al4V foams but they only colonized the superficial microspheres, whereas the cells did not fill the pores on coarse Ti6Al4V foams but they were distributed throughout most of the material. In addition, the microspheres with wide pores (coarse Ti6Al4V) stimulated higher osteoblast differentiation, as demonstrated by the Alcaline Phosphatase (ALP) activity. Our in vitro results suggest that foams with wide pore facilitate internal cell colonization and stimulate osteoblast differentiation.
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Papers by M. Punset