Revestimentos obtidos por aspersão térmica (AT) podem ser utilizados na proteção de componentes d... more Revestimentos obtidos por aspersão térmica (AT) podem ser utilizados na proteção de componentes da indústria que atuam sob condições severas de abrasão, impacto de partículas e corrosão. O objetivo deste trabalho foi avaliar a quantidade de defeitos (poros e trincas) de dois revestimentos metálicos obtidos pela técnica de AT por arco elétrico (Ligas A e B) aplicados sobre duas geometrias de substratos distintas, chapas e tubos. Os tubos revestidos permaneceram expostos às condições reais de trabalho em uma caldeira de central termelétrica movida à carvão mineral pelo período de um ano. Foram utilizadas técnicas de microscopia óptica (MO), microscopia eletrônica de varredura (MEV), análise química semi-quantitativa por Energy Dispersive Spectroscopy (EDS) e análise e processamento digital de imagens (PDI). Após exposição dos tubos em campo, a elevada rugosidade de superfície característica do processo de AT, foi reduzida. Os resultados revelaram maior percentual de trincas e poros nos revestimentos dos tubos (7,6% e 14,9% paras as ligas A e B, respectivamente) em relação às chapas (5,0% e 5,6% paras as ligas A e B, respectivamente).
Characterization of mechanical and surface finishing properties of metallic coating obtained by a... more Characterization of mechanical and surface finishing properties of metallic coating obtained by arc electric thermal spray Caracterização das propriedades mecânicas e de superfície de revestimento de revestimento metálico obtido por pulverização térmica elétrica arc
Thermoelectric power plants that use mineral coal show high wear in heat exchanger due to the act... more Thermoelectric power plants that use mineral coal show high wear in heat exchanger due to the action of several damage mechanisms associated with the impact of hard particles from the residue of burnt coal, the ashes. The employment of coatings should be given into consideration particularly for critical components, which are subject to severe erosive conditions is one of the solutions. However, the choice of material will depend on several factors, including the properties of aggressive ashes. This paper aims to characterize ashes generated by a Brazilian coal-based power plant and a FeCrNbNi-based metallic coating obtained by the electric arc spraying process. No trace of sulfur content was found in fly ashes and it was defined that wear is mainly related to the impact and energy of hard particles are the leading causes of degradation in coal-fired boiler equipment. According to the assessment, applied coating showed (5 ± 2)% by volume of pores and cracks, with 1.6% of oxides after the spraying process and hardness 35% greater than ash particles. Preliminary results in field operation suggest that the material showed relatively low wear compared to the original substrate and showed great applicability in controlling material deterioration for this purpose.
We investigate the causes of failure of a piston rod of a hydraulic cylinder, which moves a spill... more We investigate the causes of failure of a piston rod of a hydraulic cylinder, which moves a spillway floodgate of a hydroelectric power plant, after 30 years of service. The fractured piston rod is made of the AISI 410 martensitic stainless steel (condition T). The analysis shows that intergranular cracking originated on the outer surface and propagated along prior austenite grain boundaries, accompanied by corrosive attacks between martensite needles. The low performance of the piston rod can be explained by the improper heat treatment during the manufacturing process, which led to a high δferrite content, temper embrittlement, low toughness, and susceptibility to stress corrosion cracking.
Falhas em tubos de caldeiras são as maiores causas de paradas forçadas de unidades de geração ter... more Falhas em tubos de caldeiras são as maiores causas de paradas forçadas de unidades de geração termelétrica, sendo que a espessura da camada de óxido, que se forma na parede interna destes tubos é a principal causadora de falhas por sobreaquecimento. A partir dos valores medidos da camada interna de óxidos é possível estimar a vida residual do componente através de correlações com parâmetros já estabelecidos na comunidade científica. O Cepel vem desenvolvendo metodologias para estimativa de vida residual de componentes de caldeiras de usinas termelétricas, seguindo as tendências mundiais e as necessidades de seus clientes no Brasil. Com a recente aquisição de equipamento para detecção de defeitos e medições de espessura via ultrassom, tornou-se possível realizar medidas de espessura tanto da parede das tubulações das caldeiras como da camada interna de óxidos presente nas mesmas. O presente artigo apresenta uma comparação entre os resultados de medições de espessura de camada de óxid...
International Journal of Microstructure and Materials Properties, 2014
Boiler pipe failures are the most common cause of forced shutdown of power generation units. The ... more Boiler pipe failures are the most common cause of forced shutdown of power generation units. The oxide layer formed in the inner wall of those pipes is the main cause of overheating failures. From the measured value of the inner oxide layer, it is possible to estimate the remaining life of the component through correlation with parameters already established by the scientific community. The present paper compares the internal oxide layer thickness measurements of pipes performed by ultrasonic (non-destructive technique) and by metallography (destructive technique), in different ranges of thickness layers
Journal of Materials Research and Technology, 2012
Overheating due to the formation of the internal oxide layer has a large in uence on the life of ... more Overheating due to the formation of the internal oxide layer has a large in uence on the life of boiler components. The aim of this study consisted in assessing the effect of the internal oxide layer on the microstructural degradation in boiler tubes. Three samples of 2.25 Cr-1Mo superheater steel tubes were used. The methodology of the study compared the microstructures of the samples received by optical, scanning electron, and transmission electron microscopy. Tensile and hardness tests were performed. At the end of the tests it was proved the deleterious effect of the internal oxide layer on the life of the component. From the measurements of the internal oxide thickness, the remaining lives of the pipes operating under creep regime were estimated with a methodology established in the literature.
The present paper describes the development of a monitoring, analysis and diagnosis system of pow... more The present paper describes the development of a monitoring, analysis and diagnosis system of power plant equipments based on strain measurements. The objective is to help companies increase availability and reduce maintenance costs. The aim is the ...
Boiler pipe failures are the most common cause of forced shutdown of power generation units. The ... more Boiler pipe failures are the most common cause of forced shutdown of power generation units. The oxide layer formed in the inner wall of those pipes is the main cause of overheating failures. From the measured value of the inner oxide layer, it is possible to estimate the remaining life of the component through correlation with parameters already established by the scientific community. Methodologies to estimate remaining life of components in power plants have been developed by Cepel, in accordance of global tendencies and the needs of Brazilian facilities. With the recent equipment acquisition for the detection of defects and measurement of thickness by ultrasonic, it became possible to measure both the pipeline wall and the internal oxide layer thicknesses. This paper presents a comparison between internal oxide layer thickness measurements of pipes performed by ultrasonic (non-destructive technique) and by metallographic preparation associated to optical microscopy (destructive ...
The present paper describes the development of a monitoring, analysis and diagnosis system of pow... more The present paper describes the development of a monitoring, analysis and diagnosis system of power plant equipments based on strain measurements. The objective is to help companies increase availability and reduce maintenance costs. The aim is the integrity evaluation of a main steam and a hot reheat steam piping through inspection, strain monitoring and computational diagnosis. The benefits are, among others, reduction in the uncertainty of the remaining life prediction and reduction of work, through process automation and integration and real time monitoring (through the Internet) of the operational condition of the equipment. Thus, greater confidence and availability of the monitored generating unit is sought as well as cost reduction as a consequence of reduced frequency of unnecessary unit stops and greater speed in decision making due to more precise follow up of the operational condition of the target-equipment and of its remaining life.
No município de Campos dos Goytacazes, localizado no norte do Estado do Rio de Janeiro, Brasil, h... more No município de Campos dos Goytacazes, localizado no norte do Estado do Rio de Janeiro, Brasil, há uma grande produção de cerâmica vermelha, como tijolos e telhas. Estes produtos são elaborados com argilas cauliníticas, abundantes na região. No caso das telhas ...
Revestimentos obtidos por aspersão térmica (AT) podem ser utilizados na proteção de componentes d... more Revestimentos obtidos por aspersão térmica (AT) podem ser utilizados na proteção de componentes da indústria que atuam sob condições severas de abrasão, impacto de partículas e corrosão. O objetivo deste trabalho foi avaliar a quantidade de defeitos (poros e trincas) de dois revestimentos metálicos obtidos pela técnica de AT por arco elétrico (Ligas A e B) aplicados sobre duas geometrias de substratos distintas, chapas e tubos. Os tubos revestidos permaneceram expostos às condições reais de trabalho em uma caldeira de central termelétrica movida à carvão mineral pelo período de um ano. Foram utilizadas técnicas de microscopia óptica (MO), microscopia eletrônica de varredura (MEV), análise química semi-quantitativa por Energy Dispersive Spectroscopy (EDS) e análise e processamento digital de imagens (PDI). Após exposição dos tubos em campo, a elevada rugosidade de superfície característica do processo de AT, foi reduzida. Os resultados revelaram maior percentual de trincas e poros nos revestimentos dos tubos (7,6% e 14,9% paras as ligas A e B, respectivamente) em relação às chapas (5,0% e 5,6% paras as ligas A e B, respectivamente).
Characterization of mechanical and surface finishing properties of metallic coating obtained by a... more Characterization of mechanical and surface finishing properties of metallic coating obtained by arc electric thermal spray Caracterização das propriedades mecânicas e de superfície de revestimento de revestimento metálico obtido por pulverização térmica elétrica arc
Thermoelectric power plants that use mineral coal show high wear in heat exchanger due to the act... more Thermoelectric power plants that use mineral coal show high wear in heat exchanger due to the action of several damage mechanisms associated with the impact of hard particles from the residue of burnt coal, the ashes. The employment of coatings should be given into consideration particularly for critical components, which are subject to severe erosive conditions is one of the solutions. However, the choice of material will depend on several factors, including the properties of aggressive ashes. This paper aims to characterize ashes generated by a Brazilian coal-based power plant and a FeCrNbNi-based metallic coating obtained by the electric arc spraying process. No trace of sulfur content was found in fly ashes and it was defined that wear is mainly related to the impact and energy of hard particles are the leading causes of degradation in coal-fired boiler equipment. According to the assessment, applied coating showed (5 ± 2)% by volume of pores and cracks, with 1.6% of oxides after the spraying process and hardness 35% greater than ash particles. Preliminary results in field operation suggest that the material showed relatively low wear compared to the original substrate and showed great applicability in controlling material deterioration for this purpose.
We investigate the causes of failure of a piston rod of a hydraulic cylinder, which moves a spill... more We investigate the causes of failure of a piston rod of a hydraulic cylinder, which moves a spillway floodgate of a hydroelectric power plant, after 30 years of service. The fractured piston rod is made of the AISI 410 martensitic stainless steel (condition T). The analysis shows that intergranular cracking originated on the outer surface and propagated along prior austenite grain boundaries, accompanied by corrosive attacks between martensite needles. The low performance of the piston rod can be explained by the improper heat treatment during the manufacturing process, which led to a high δferrite content, temper embrittlement, low toughness, and susceptibility to stress corrosion cracking.
Falhas em tubos de caldeiras são as maiores causas de paradas forçadas de unidades de geração ter... more Falhas em tubos de caldeiras são as maiores causas de paradas forçadas de unidades de geração termelétrica, sendo que a espessura da camada de óxido, que se forma na parede interna destes tubos é a principal causadora de falhas por sobreaquecimento. A partir dos valores medidos da camada interna de óxidos é possível estimar a vida residual do componente através de correlações com parâmetros já estabelecidos na comunidade científica. O Cepel vem desenvolvendo metodologias para estimativa de vida residual de componentes de caldeiras de usinas termelétricas, seguindo as tendências mundiais e as necessidades de seus clientes no Brasil. Com a recente aquisição de equipamento para detecção de defeitos e medições de espessura via ultrassom, tornou-se possível realizar medidas de espessura tanto da parede das tubulações das caldeiras como da camada interna de óxidos presente nas mesmas. O presente artigo apresenta uma comparação entre os resultados de medições de espessura de camada de óxid...
International Journal of Microstructure and Materials Properties, 2014
Boiler pipe failures are the most common cause of forced shutdown of power generation units. The ... more Boiler pipe failures are the most common cause of forced shutdown of power generation units. The oxide layer formed in the inner wall of those pipes is the main cause of overheating failures. From the measured value of the inner oxide layer, it is possible to estimate the remaining life of the component through correlation with parameters already established by the scientific community. The present paper compares the internal oxide layer thickness measurements of pipes performed by ultrasonic (non-destructive technique) and by metallography (destructive technique), in different ranges of thickness layers
Journal of Materials Research and Technology, 2012
Overheating due to the formation of the internal oxide layer has a large in uence on the life of ... more Overheating due to the formation of the internal oxide layer has a large in uence on the life of boiler components. The aim of this study consisted in assessing the effect of the internal oxide layer on the microstructural degradation in boiler tubes. Three samples of 2.25 Cr-1Mo superheater steel tubes were used. The methodology of the study compared the microstructures of the samples received by optical, scanning electron, and transmission electron microscopy. Tensile and hardness tests were performed. At the end of the tests it was proved the deleterious effect of the internal oxide layer on the life of the component. From the measurements of the internal oxide thickness, the remaining lives of the pipes operating under creep regime were estimated with a methodology established in the literature.
The present paper describes the development of a monitoring, analysis and diagnosis system of pow... more The present paper describes the development of a monitoring, analysis and diagnosis system of power plant equipments based on strain measurements. The objective is to help companies increase availability and reduce maintenance costs. The aim is the ...
Boiler pipe failures are the most common cause of forced shutdown of power generation units. The ... more Boiler pipe failures are the most common cause of forced shutdown of power generation units. The oxide layer formed in the inner wall of those pipes is the main cause of overheating failures. From the measured value of the inner oxide layer, it is possible to estimate the remaining life of the component through correlation with parameters already established by the scientific community. Methodologies to estimate remaining life of components in power plants have been developed by Cepel, in accordance of global tendencies and the needs of Brazilian facilities. With the recent equipment acquisition for the detection of defects and measurement of thickness by ultrasonic, it became possible to measure both the pipeline wall and the internal oxide layer thicknesses. This paper presents a comparison between internal oxide layer thickness measurements of pipes performed by ultrasonic (non-destructive technique) and by metallographic preparation associated to optical microscopy (destructive ...
The present paper describes the development of a monitoring, analysis and diagnosis system of pow... more The present paper describes the development of a monitoring, analysis and diagnosis system of power plant equipments based on strain measurements. The objective is to help companies increase availability and reduce maintenance costs. The aim is the integrity evaluation of a main steam and a hot reheat steam piping through inspection, strain monitoring and computational diagnosis. The benefits are, among others, reduction in the uncertainty of the remaining life prediction and reduction of work, through process automation and integration and real time monitoring (through the Internet) of the operational condition of the equipment. Thus, greater confidence and availability of the monitored generating unit is sought as well as cost reduction as a consequence of reduced frequency of unnecessary unit stops and greater speed in decision making due to more precise follow up of the operational condition of the target-equipment and of its remaining life.
No município de Campos dos Goytacazes, localizado no norte do Estado do Rio de Janeiro, Brasil, h... more No município de Campos dos Goytacazes, localizado no norte do Estado do Rio de Janeiro, Brasil, há uma grande produção de cerâmica vermelha, como tijolos e telhas. Estes produtos são elaborados com argilas cauliníticas, abundantes na região. No caso das telhas ...
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