The understanding of the corrosion mechanisms of magnesium-based alloys is crucial for their utilisation in lightweight engineering, due to their minimal corrosion resistance preventing its widespread application. In this investigation to improve the hardness, corrosive and wear behaviour of a AZ31 by its incorporation of Tungsten Carbide (WC) ceramic reinforcement and wear behaviour with varying levels of reinforcement (2.5, 5.0 and 7.5 wt.%) weight percentage. The alloy and composites were manufactured via liquid metallurgy The microstructure analysis, XRD, hardness, salt spray corrosion analysis varying (2.5 -5.0%) Nacl solutions and dry sliding wear behavior were evaluated using pin-on-disc tests under loads of 10-60 N. The results indicates that fine distribution of reinforcement and free from casting defects through SEM and presence of particles is confirmed with EDS and XRD analysis. The improved hardness up to 78.5% on AZ7.5 as compared to all fabricated samples. The formation of stable Mg (OH)2 as protective layer on AZ5.0 shows a better corrosion resistance in all NaCl conditions. The improved wear resistance on AZ7.5 is attributed to the development of a tribolayer, it improves the resistance to applied load. The SEM micrograph reveals the plastic deformation observed in AZ0 and the mild wear behaviour exhibited by the AZ7.5 composite.
This work presents a comparison between the Remote Field Testing (RFT) and Internal Rotary Inspection System (IRIS) non-destructive testing (NDT) techniques. Such a comparison aims to assess the influence of the inspector experience on the RFT inspection process, as well as to evaluate whether the RFT technique has an inspection capability equivalent to the IRIS test. By using inspection data, a statistical analysis was conducted based on the results from three different RFT inspectors. Then, considering a third technique (3D Scanning) applied to sections extracted from tubes (destructive case) as a reference basis, the statistical equivalence of both NDT techniques was evaluated. Finally, to assess the accuracy of the analyses conducted by the RFT inspectors and the comparison between the RFT and IRIS techniques, artificial intelligence (AI) tools were employed to measure the success and error rates of corrosion detection via the RFT case. The results show equivalence between the NDT techniques and, despite the interpretation challenges with the RFT case, the subjectivity by the inspectors with its inspection process was considered low. The AI classification results indicated that the generated network was capable of classifying the corrosion effectively, hence supporting the equivalence between the RFT and IRIS techniques.
Residual stress evaluation in welded joints is of major importance, since its underestimation or lack of control can lead to deformations of welded components, to its mechanical properties' deterioration or even to failure in service. Various destructive and non-destructive techniques exist for measuring residual stress, each differing in complexity, cost, and accuracy. This study investigates the applicability of the hole-drilling method combined with Electronic Speckle Pattern Interferometry (ESPI) for residual stress evaluation specifically in welded joints, where surface conditions and material properties differ from the base metal due to reinforcement convexity, surface irregularities, and microstructural changes. The methodology involved initial equipment calibration using known strain levels, followed by residual stress measurements on bead-on-plate samples - produced with and without filler material. The analysis focused on different weld regions (fusion zone, heat-affected zone, and base metal), considering both longitudinal and transverse stress components. Calibration results showed a mean measurement error of 5.8% and a coefficient of variation around 6%. For the welded beads, the ESPI-based hole-drilling method demonstrated coherent residual stress distributions consistent with theoretical models. Higher precision was observed for the transverse stress component and in samples welded without filler material, while the longitudinal stresses in the heat-affected zone of the welds with filler addition exhibited greater variability due to local metallurgical and geometrical effects. Overall, the study confirms that the combined hole-drilling and ESPI technique is a viable and reliable approach for residual stress measurement in welded joints, provided that factors such as measurement depth, surface condition, and local stress gradients are carefully managed.
Resumo Macrossegregações em soldas são imperfeições de natureza metalúrgica que, na maioria das vezes, se formam durante a união de materiais dissimilares, podendo comprometer a qualidade da região soldada. O presente estudo teve como objetivo analisar a formação de macrossegregações durante a simulação de reparos por soldagem em regiões degradadas por cavitação, utilizando diferentes variantes do processo MIG/MAG e envolvendo a união de um aço inoxidável austenítico e um aço inoxidável martensítico. Foram realizados depósitos do tipo bead on plate empregando distintos modos de transferência metálica: curto-circuito convencional com e sem tecimento, curto-circuito controlado por CMT (Cold Metal Transfer), globular, spray e pulsado. Foi utilizado o aço inoxidável austenítico AISI 309 como metal de adição e o aço inoxidável martensítico grau CA-6NM como material-base. A caracterização microestrutural revelou a presença de macrosegregações na forma de ilhas e penínsulas na interface soldada entre os materiais. Essas imperfeições foram menos expressivas nos processos com transferência CMT e curto-circuito convencional sem tecimento quando comparadas às demais variantes. Dentre os diversos modos de transferência analisados, o modo por curto-circuito, tanto o convencional quanto o controlado por CMT, destacou-se por apresentar menor formação de macrossegregações, sendo o CMT o mais eficaz na obtenção de baixos índices de diluição.
Resumo Neste trabalho foram analisados dados dos experimentos em soldagem MIG/MAG, realizados no modo de operação por curto-circuito, utilizando três gases: 100% argônio, argônio mais 25% de dióxido de carbono e 100% dióxido de carbono, possibilitando análises abrangentes dos parâmetros: tempo de curto-circuito; tempo de arco aberto; tensão de curto-circuito; tensão de arco aberto; taxa de subida da corrente; número de curtos e tensão de referência. Foram realizados testes de correlação (Pearson, Spearman, Kendall) para analisar a qualidade dos modelos, incluindo a aplicação de testes de Shapiro-Wilk para verificar a normalidade dos resíduos sendo possível criar uma matriz de correlações com os parâmetros e gases testados. A correlação entre o tempo de arco aberto e o número de curtos, e para o tempo de arco aberto e a taxa de subida da corrente apresentaram forte correlação para todos os gases. As correlações entre a taxa de subida da corrente e o número de curtos, o tempo de curto e a tensão de curto-circuito, assim como a correlação entre a tensão de curto-circuito e a tensão de referência, demonstraram menor significância para todos os gases. Em relação à análise por série temporal, os modelos ARIMA e ETS foram ajustados e avaliados com métricas específicas, indicando a necessidade de melhorias no modelo para aumentar a precisão das previsões.
