NUNES, C. S. Caracterização de fases e análise de trincas em junta soldada de Inconel 625 e aço 9Cr-1Mo após envelhecimento. 2006. 105 f. Dissertação (Mestrado em Ciência de Materiais) – Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2006. / Submitted by Marlene Sousa (mmarlene@ufc.br) on 2016-03-31T13:01:03Z No. of bitstreams: 1 2006_dis_csnunes.pdf: 11133016 bytes, checksum: 2052908ae018bb93d27596c930c78e76 (MD5) / Approved for entry into archive by Marlene Sousa(mmarlene@ufc.br) on 2016-03-31T17:59:22Z (GMT) No. of bitstreams: 1 2006_dis_csnunes.pdf: 11133016 bytes, checksum: 2052908ae018bb93d27596c930c78e76 (MD5) / Made available in DSpace on 2016-03-31T17:59:22Z (GMT). No. of bitstreams: 1 2006_dis_csnunes.pdf: 11133016 bytes, checksum: 2052908ae018bb93d27596c930c78e76 (MD5) Previous issue date: 2006-11-13 / The discoveries of new oil deposits with right rates acidity caused the refining units of crudes use facilities modified and adapted to this condition. In order to increase the corrosion resistance and reduce the risk of failure during the operation are used alloy steels of type Cr-Mo, A-213 T-9 (9%Cr e 1%Mo) in the tubes in refining plants configuring tubes ASTM A335 GR P 9, as API RP-530, designed for continuous service in media containing sulfide and high temperature. These tubes are coated with aluminum and welded by TIG welding process, with the root password nickel alloy, Inconel 625, welding rod ER-NiCrMo-3 and fill electrode E 505. Thus, it studied the behavior of nickel alloy deposited on the union of the tubes, their properties and has been the characterization of phases present in the material after aging. For this, we used samples from 02 tubes A-213 T-9 coated with aluminum and welded together under the same conditions of the tubes of the furnaces of the units of petroleum refining. The samples were exposed to temperatures in the range of operation (500 º C to 700 º C) for periods of 10h, 100h, 500h e 1000h. / As descobertas de novas jazidas de petróleo com índices de acidez cada vez maiores fizeram com que as unidades de refino de óleos crus utilizassem instalações modificadas e adaptadas para essa condição. Visando aumentar a resistência à corrosão e a reduzir o risco de falha durante a operação são empregados os aços liga do tipo Cr-Mo, A-213 T-9 (9%Cr e 1%Mo) nos tubos de fornos nas usinas de refino configurando os tubos ASTM A335 GR P 9, conforme API RP-530, projetados para serviço contínuo em meios contendo sulfeto e elevada temperatura. Esses tubos são revestidos internamente com alumínio e soldados através do processo de soldagem TIG, tendo como passe raiz liga de níquel, Inconel 625, vareta ER-NiCrMo-3 e preenchimento com eletrodo E 505. Dessa forma, estudou-se o comportamento da liga de níquel depositada na união dos tubos, suas propriedades e realizou-se a caracterização de fases presentes no material após o envelhecimento. Para isto, utilizou-se amostras de 02 tubos A-213 T-9 revestidos com alumínio e unidos por solda nas mesmas condições dos tubos dos fornos das unidades de refino de petróleo. As amostras foram expostas as temperaturas no intervalo de operação (500ºC à 700ºC) por períodos de 10h, 100h, 500h e 1000h.

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As curvas de polarização potenciodinâmicas cíclicas da liga de níquel Inconel 625, em solução de NaCl 3,56 %, pH 7,5, desaerada e a temperatura ambiente, obtidas com base na metodologia descrita na norma ASTM G61, foram estudadas com o objetivo de interpretá-las, especialmente no trecho após a reversão da polarização. Para esse estudo, foram realizadas análises complementares por MEV/EDS e por espctroscopia Raman da superfície do eletrodo de trabalho e determinação qualitativa por EDS da composição do eletrólito coletado nas vizinhas do eletrodo de trabalho. Medidas de pH e determinação do teor de O2 do eletrólito junto ao eletrodo de trabalho também foram feitas. Os resultados obtidos mostraram que, entre o potencial de circuito aberto até potencial de quebra (Eb), da ordem de 0,600 V (ECS), a curva de polarização apresenta um comportamento passivo com tendência a atingir a densidade de corrente da ordem de 10-6 A/cm². Nessa região, ocorre o espessamento da camada devido à formação principalmente de Cr2O3. Após Eb, ocorre a mudança na inclinação da curva, devido à ocorrência da reação de oxidação da água, comprovada pela acidificação do eletrólito. No potencial de 0,750 V (ECS) ocorre uma inflexão na curva, causando a diminuição discreta da corrente, atribuída à formação de MoO42- (gel) que evita a incorporação de ânions como Cl- ou OH-, dificultando, porém não evitando, a oxidação/dissolução da camada passiva, comprovada pela presença de íons de Cr e de Ni no eletrólito, caracterizando uma região transpassiva. Após a reversão da polarização no potencial de 1,130 V (ECS), a curva apresenta uma histerese positiva, com valores de densidades de correntes menores em relação ao mesmo potencial aplicado durante a polarização direta, indicando a ocorrência de repassivação devido principalmente à formação de uma camada rica em Mo sobre a liga, cuja formação pode ser atribuída à transformação do molibdato para o óxido MoO3 decorrente da forte acidificação do eletrólito verificado nesse trecho da curva. Ainda, após a inversão da polarização, ocorre a transição da corrente anódica para catódica em um potencial próximo de 0,720 V (ECS). Do potencial de 0,600 V (ECS) até 0,200 V (ECS), observa-se uma região de passivação secundária, atribuída à formação do MoO3 de maneira mais significativa. Ao final a densidade de corrente volta a aumentar, indicando o início da oxidação/dissolução do MoO3 para Mo3+. / Cyclic potentiodynamic polarization curves of the nickel alloy Inconel 625 in 3.56 % NaCl solution, pH 7.5, deaerated and at ambient temperature, obtained according to the ASTM G61, were studied in order to interpret them, especially after the reversion of the scanning direction. For this study, complementary analyzes by MEV/EDS and by Raman spectroscopy of the working electrode surfaces as well as EDS analyses of the electrolyte collected near the working electrode were carried out. The pH values and O2 content of the electrolyte near the working electrode were also obtained. From the open circuit potential (OPC) up to breakdown potential (Eb), at about 0,600 V (ECS), the polarization curve presents a passive behavior with a tendency to reach the current density of 10-6 A/cm². In this region, the thickening of the passive film takes place mainly due to the formation of Cr2O3. After Eb, a change of the curve slope occurs due to the oxygen evolution reaction which is confirmed by the acidification of the electrolyte. At the 0,750 V (ECS) potential, an inflection of the curve is observed causing a discrete decrease in the current which was attributed to the formation of MoO42- (gel) which, in turn, avoids the incorporation of anions as Cl- or OH- in the passive film. This fact makes the oxidation/dissolution of the passive film difficult but does not avoid it since Cr and Ni ions were detected in the electrolyte after the inflection, characterizing a transpassive region. After the reversion of the scanning direction at the potential 1,130 V (ECS), the curve shows a positive hysteresis with lower current densities than the values obtained at the same potential applied during the direct polarization. This indicates the occurrence of repassivation mainly due to the formation of a Mo rich layer on the alloy whose formation can be attributed to the transformation of the molybdate to the MoO3 because of the strong acidification of the electrolyte. After the reversion of the polarization, a transition from the anodic current to cathodic occurs at a potential close to 0,720 V (ECS). From the potential of 0,600 V (ECS) up to 0,200 V (ECS), a secondary passivation region is observed which was attributed to the significant formation of MoO3. At the end of the reverse polarization, the current increases again, indicating the initiation of the oxidation/dissolution of MoO3 to Mo3+.

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This diploma thesis is focused on description of the properties of a layer of Inconel 718 applied on austenitic steel AISI 304 by the Cold Spray and subsequently remelted by electron beam. The first part presents the Cold Spray with its properties, advantages and disadvantages, and also describes the principle of electron beam remelting and other possible uses of electron beam, for example welding, drilling, heat treatment etc. The second part describes the material and the methods used for the preparation and evaluation of the samples. There are evaluated the porosity, microstructure and microhardness of the layers applied by the Cold Spray and these properties are further compared with the properties of the same layers remelted by electron beam. In conclusion, the results of the porosity of the layers applied by the Cold Spray are discussed with the literature and the results of electron beam remelting are only partially described here, because it was not possible to find literature about this topic. There are also suggestions for further research of the properties of this layers, which is necessary to know before implementing this method of producing layers for commercial production.

Increasing tool life is a significant objective in production. Achieving this objective in a machining process poses a significant challenge, especially during cutting hard-to-cut materials such as superalloys, due to the severe tool chipping/failure at the beginning of the cut. Although numerous attempts have been carried out to improve tool performance and prolong tool life during the machining of difficult-to-cut materials over the past several years, researchers have not obtained sufficient control over sudden tool failure/chipping. The focus of this study is to prolong tool life and control tool chipping by developing an ultra-soft deposited layer on the cutting tool that can protect it during the machining of difficult-to-cut materials such as Inconel 718. In the current study, an ultra-soft layer of material is deposited on the tool through two different techniques; a typical physical vapor deposition (PVD) technique and a novel developed method called “pre-machining”. In the PVD method, the soft layer is deposited under a high vacuum environment using a PVD coater. In the novel pre-machining method, the soft layer is deposited through a very short machining process involving Al-Si. It should be mentioned that soft coatings have never been used before for machining applications of difficult-to-cut materials including Inconel 718. This study shows that in contrast to what is expected, depositing an ultra-soft layer on the cutting tool significantly improves tool performance, by reducing chipping, and improving the machined surface integrity during cutting of Inconel 718. The obtained results show up to a 500% ± 10% improvement in tool life and around a 150% ± 10% reduction in cutting forces. Significant reductions in work hardening, residual stress, and surface roughness on the machined surface were other main achievements of the current study. / Thesis / Doctor of Philosophy (PhD) / Inconel 718 is considered to be a difficult-to-cut material due to its poor machinability. Significant tool failure at the early stage of cutting is the main challenge of machining this material and is the most significant contributing factor to its high manufacturing costs. Studies show that the common methods used to tackle this issue have not been completely successful. The goal of the present study is to tackle the machining challenges of Inconel 718 by developing tool coatings that meet the specific needs of the material to eliminate tool failure and thereby improve overall machining performance. For this purpose, a new tool coating material and a novel deposition technique that can be used as an alternative for commonly used coatings were developed in this study to improve the tool performance during the machining of Inconel 718. In addition, thorough studies have been carried out to gain a better understanding of the dominant wear phenomena and tool surface treatments that result in an improvement in the machinability of Inconel 718.

No description available.

Nickel super alloy Inconel 718 was tested and compared to Haynes 230 using Gleeble and Varestraint mechanical test methods. Hot cracking susceptibility was examined in either alloy using a sub-scale Varestraint test method at 5 augmented strain levels: 0.25%, 05.%, 1%, 2%, and 4%. Maximum crack length, total crack length, and number of cracks were measured for each strain level. Gleeble hot ductility on-heating and on-cooling tests were performed on both alloys. Inconel 718 was tested on-heating at target temperatures of 1600˚F, 2000˚F, 2100˚F, 2200˚F, and on cooling at 1600˚F, 1700˚F, 1800˚F, 1900˚F, and 2100˚F. Haynes 230 was tested on-heating at target temperatures of 2050 ˚F, 2200 ˚F, 2240 ˚F, 2330 ˚F, and on-cooling at 1800 ˚F, 1900 ˚F, 1990 ˚F, 2040 ˚F, 2090 ˚F, 2100 ˚F, 2140 ˚F, and 2190 ˚F. Ductility in Gleeble samples was measured in a reduction of surface area. A nil-strength temperature was established for either alloy. The nil-strength temperature was 2251˚F and 2411˚F, for Inconel 718 and Haynes 230, respectively. The nil ductility temperature <5% R/A) was 2188˚F for Inconel 718 and 2341˚F for Haynes 230. Ductility recovery temperature occurred at 1924˚F for Inconel 718 and 2147˚F for Haynes 230. The brittle temperature range was determined to be 326˚F for Inconel 718 and 228˚F for Haynes 230. Varestraint testing revealed that Inconel 718 had a lower threshold strain for crack initiation than Haynes 230 (0.5% vs 1%), and a higher number of cracks, as well as a larger maximum crack length, at every strain level. These results show a greater tendency for liquation cracks to form in Inconel 718 than in Haynes 230.

At temperatures above 0.5 Tm and in aggressive atmospheres predicting alloy performance is particularly challenging. Nickel alloys used in regimes where microstructure and properties are altered dynamically present unique requirements. Exposure may alter properties with unexpected early failure. The Gleeble is a valuable tool for investigation and simulation of thermo-mechanical properties of an alloy in various regimes up to the threshold of melting. In this study, four regimes of temperature and strain rate were simulated in an argon atmosphere to both investigate and document normal and abnormal failure modes. Commercial Inconel 601 was tested in selected regimes and in two treatments (as received and strain aged). Next two exposed conditions (TEOS and Hydride) were tested. Slow strain-rate and high temperature produced brittle intergranular fracture. Exposure at elevated temperature to process gases reduced both strength and ductility in both TEOS and Hydride. TEOS exposure reduced reduction in area in the alloy significantly more than the Hydride exposure.

No description available.