Cesar Giron Camerini

Magnetic and Electrochemical Techniques as Tools to Detect Deleterious Phases in Duplex Stainless Steels

The development of techniques to detect deleterious phases in duplex and super duplex stainless steel has a great technical-scientific appeal. However, establishing a quality control of these steels using a unique technique of inspection requires an attentive analysis about its limits and sensibility of detections. Thus, the current work compares magnetic techniques based on eddy current methods and electrochemical potentiokinetic reactivation with double loop to detect deleterious phases in duplex stainless steel. The limitations and advantages of each technique are discussed mainly concerning the viability to detect sigma phase and chromium nitride.

Saturated low frequency eddy current technique applied to microstructure phase quantification in duplex stainless steel

Duplex stainless steel (DSS) presents a good combination of mechanical properties and high corrosion resistance. Its microstructure is composed of two phases with different physical properties: delta ferrite and gamma austenite. The best properties of DSS for in service applications are achieved when these phases are in equal proportions. However, exposition to high temperatures, may entail undesired consequences impairing the mechanical and corrosion properties of the material. Eddy current testing (ECT) has already been used for DSS inspection and microstructure characterization, mainly to detect the presence of deleterious phases, such as sigma. However, conventional ECT was not able to quantify different amounts of austenite and ferrite in the absence of deleterious phases. The present study focuses on the experimental and computational problem of DSS inspection using ECT in saturated magnetic conditions in order to identify different amounts of austenite and ferrite within the DSS microstructure. Samples containing ferrite to austenite ratio equal to 50/50, 70/30 and 80/20 respectively were brought to saturation as designed in the simulations and the ECT was applied presenting a very good result. Saturated low frequency ECT condition proved to be a reliable methodology in quantifying delta ferrite and gamma austenite phases in DSS.

Eddy Current Transducer Dedicated for Sigma Phase Evaluation in Duplex Stainless Steel

The paper describes a new transducer dedicated for evaluation of a duplex stainless steel (DSS). Different phases which exist in DSS have influence on mechanical as well as on electrical properties. Therefore, an eddy current transducer was utilized. In order to achieve high sensitivity, a differential type of the transducer was selected. The performance of the transducer was verified by utilizing the samples which had a different amount of sigma phase.

In-Line Inspection Tool with Eddy Current Instrumentation for Fatigue Crack Detection

Eddy current transducer with sensing coils placed orthogonally and connected in differential mode was introduced to evaluate fatigue cracks in clad pipeline circumferential welds. A dedicated embedded electronic hardware was developed to drive the transducer and measure the electrical complex impedance of the coils, and was specifically designed for operation under autonomous in-line inspection tool. In the laboratory experiments, an automated inspection was performed with the goal to evaluate transducer’s detectability, and different scanning speed was tested to reproduce in service situation. The results have confirmed that the introduced eddy current transducer is a potential solution for fatigue crack detection in clad circumferential weld root, while the hardware developed presented a reasonable SNR reaching the data rate required to be incorporated in an autonomous in-line inspection tool.

AVALIAÇÃO DO FERRITOSCÓPIO PARA QUANTIFICAÇÃO DE FERRITA DELTA EM AÇOS INOXIDÁVEIS SUPERDUPLEX

* Contribuição técnica ao 72o Congresso Anual da ABM – Internacional e ao 17o ENEMET Encontro Nacional de Estudantes de Engenharia Metalúrgica, de Materiais e de Minas, parte integrante da ABM Week, realizada de 02 a 06 de outubro de 2017, São Paulo, SP, Brasil. AVALIAÇÃO DO FERRITOSCÓPIO PARA QUANTIFICAÇÃO DE FERRITA DELTA EM AÇOS INOXIDÁVEIS SUPERDUPLEX* Cesar Giron Camerini Vitor Manoel de Araújo Silva Iane de Araújo Soares Rafael Wagner Florêncio dos Santos Julio Endress Ramos João Marcio de Castilho Santos Gabriela Ribeiro Pereira Resumo Os aços inoxidáveis bifásicos superduplex estão presentes em diversos setores da engenharia devido a versatilidade oferecida em termos de propriedades mecânicas e resistência à corrosão. Para garantir a qualidade destes aços, avaliar o teor de ferrita presente na microestrutura é de grande relevância para indústria uma vez que diversas propriedades do material dependem do controle deste teor. Durante a fabricação de equipamentos ou inspeções de campo uma das formas mais viáveis de monitorar o teor de ferrita é através do ferritoscópio, dada sua portabilidade e fácil interpretação. No entanto, observou-se que a forma usual de calibração do ferritoscópio pode levar a medidas imprecisas, principalmente na avaliação dos aços superduplex. A fim de analisar esta influência, foram realizados diferentes testes de caracterização microestrutural através de microscopia ótica, difração de raio-x e o magnetômetro de amostra vibrante, para confrontar com medidas obtidas com ferritoscópio. Conclui-se que para elevados teores de ferrita, a calibração do ferritoscópio realizada a partir dos padrões fornecidos pelos fabricantes apresentam desvios significativos dos teores encontrados a partir da caracterização com equipamentos de laboratório. O presente trabalho apresenta uma solução para utilização do ferritoscópio para uma quantificação mais acurada do teor de ferrita nos aços inoxidáveis superduplex. Palavras-chave: Aço inoxidável superduplex; Ferritoscópio; procedimentos de calibração; Difração de raio-x.

2015 WFNDEC eddy current benchmark modeling of impedance variation in coil due to a crack located at the plate edge

The 2015 World Federation of NDE Centers (WFNDEC) eddy current benchmark problem involves the inspection of two EDM notches placed at the edge of a conducting plate with a pancake coil that runs parallel to the plate’s edge line. Experimental data consists of impedance variation measured with a precision LCR bridge as a XY scanner moves the coil. The authors are pleased to present the numerical results obtained with commercial FEM packages (OPERA 3-D). Values of electrical resistance and inductive reactance variation between base material and the region around the notch are plotted as function of the coil displacement over the plate. The calculations were made for frequencies of 1 kHz and 10 kHz and agreement between experimental and numerical results are excellent for all inspection conditions. Explanations are made about how the impedance is calculated as well as pros and cons of the presented methods.

Electromagnetic non-destructive technique for duplex stainless steel characterization

Duplex stainless steel (DSS) is a two-phase (ferrite and austenite) material, which exhibits an attractive combination of mechanical properties and high corrosion resistance, being commonly employed for equipment of petrochemical plants, refining units and oil & gas platforms. The best properties of DSS are achieved when the phases are in equal proportions. However, exposition to high temperatures (e.g. welding process) may entail undesired consequences, such as deleterious phases precipitation (e.g. sigma, chi) and different proportion of the original phases, impairing dramatically the mechanical and corrosion properties of the material. A detailed study of the magnetic behavior of DSS microstructure with different ferrite austenite ratios and deleterious phases content was accomplished. The non destructive method evaluates the electromagnetic properties changes in the material and is capable to identify the presence of deleterious phases into DSS microstructure.

2012 eddy current benchmark modeling of impedance variation in coil due to a thin longitudinal through-wall notch in an inconel 600 tube

The 2012 Eddy Current Benchmark Problem involves the inspection of an inconel pipe using an internal pancake coil situated with its axis perpendicular to the axis of the pipe. The experimental data were supported by the Benchmark Eddy Current 2012, as released by the World Federation of Non Destructive Evaluation Centers (WFNDEC). The software OPERA 3D and COMSOL were used by the authors to solve the proposed simulation problem. The simulated results were in good agreement with the experimental ones. However some simulated results exhibited a small variation in the impedance and electrical resistance between the base material and the region around the notch. The values of these changes were plotted as a function of the displacement of the sensor over the notch region. The calculations were made for frequencies of 25kHz to 200kHz. A good agreement was obtained at low frequency. However, the simulation at high frequencies presented differences, which can be attributed to the mesh refinement. The finite elem...

The Sigma Phase Evaluation in Duplex Stainless Steel Using ECT Method

An eddy current method was applied to evaluate amount of sigma phase in duplex stainless steel. In the preliminary experiments several transducers configuration were considered. The performance of the transducers were verified utilizing samples having different amount of sigma phase. The configurations presenting the greatest possibility of evaluation of sigma phase were chosen for further experiments. In this paper a dedicated transducer operating in differential mode will be presented. The results will be shown and discussed.