Evaluation of standard API casing connections and parametric API buttress improvement by finite element analysis.

Threaded and coupled connections generally present a non-uniform stress distribution, which is related to the higher stiffness of the box when compared to the pin. The non-uniform stress distribution can contribute to fatigue cracks and other failure modes in high pressure oil wells. An API 5CT P110 steel obtained from a seamless pipe was mechanically characterized. FEA models were carried out to investigate and compare two API casing connections under make-up torque and tensile efforts. A parametric study was performed using numerical models to determine the influence of some geometric features on the behavior of the API Buttress threaded connection. The API Buttress connection supported higher tensile loads than the API Short Round, however both standard connections showed high stress concentration in the last engaged thread and a non-uniform stress distribution. The manufacturing of grooves at the first and the last engaged threads proved to be an efficient way to reduce the stress concentration of Buttress casing connection and could be an alternative to the development of new products

Evaluation of hydrogen-Induced cracking resistance of the In625 laser coating system on a C-Mn steel substrate.

The corrosion of C-Mn steels in the presence of hydrogen sulfide (H2S) represents a significant challenge to oil production and natural gas treatment facilities. The failure mechanism induced by hydrogen-induced cracking (HIC) in a Inconel 625 coating / C-Mn steel has not been extensively investigated in the past. In the present work, an API 5CT steel was coated with In625 alloy using laser cladding and the HIC resistance of different regions, such as the coating surface, the substrate and HAZ, were evaluated. SEM observations illustrated that all HIC cracks were formed at the hard HAZ after 96h of exposure. No HIC cracks were observed in the substrate and the In625 coating after the same exposure duration. Pitting was recorded in the substrate caused by non-metallic inclusion dissolving

Laser cladding and thermal spray coatings on steel pipe serving the oil and gas industry.

Different coating systems were characterized using a commercial API 5CT steel grade L80 type 1, which is commonly used in the oil and gas industry. Two Ni-based alloys and one Co-based alloy were deposited by laser cladding. Two coatings were deposited (Ni-based alloy and a composite W-C/Co-base) by means of thermal spray process. It has been shown the presence of a hard heat affected zone (HAZ) in the substrate for the as-laser deposited coating. The main explanation for this HAZ is devoted to the heat gradient causing a gradient on the prior austenite grain size and consequently different martensite hardness along the HAZ. For the thermal sprayed coatings, no HAZ was formed due to low heat input process. All the studied coating systems seem to be very interesting for different technically demanding applications, such as, stress sulfide corrosion and wear resistance

Efeito de diferentes tratamentos t?rmicos sobre microestrutura e microdureza de um sistema a?o C-Mn/revestimento de inconel 625.

A utiliza??o de tubos de a?o C-Mn na ind?stria de ?leo e g?s ? muito comum desde o nascimento desta ind?stria. Mesmo com a grande evolu??o da metalurgia destes a?os ao longo das ?ltimas d?cadas, o desafio de desempenho em ambientes severos de corros?o devido ?s caracter?sticas reativas (H2S, CO2) do petr?leo e seus derivados, imp?em uma nova era para a fabrica??o de tubos. A solu??o tecnol?gica mais direta seria a utiliza??o de a?os com alta liga (Ni, Cr) e/ou superligas de n?quel. No entanto, os custos de produ??o tornariam invi?veis pelo alto custo destes materiais. Neste contexto, ? crescente iniciativas de pesquisas para o desenvolvimento de overlay e/ou cladding, ou seja, revestimentos de a?os C-Mn usando superligas de n?quel e a?os inoxid?veis. Neste trabalho, foi utilizada a deposi??o de uma camada da superliga de n?quel Inconel 625 atrav?s do processo laser. Uma das desvantagens da deposi??o a laser ou qualquer outro processo de fus?o ? a forma??o de uma regi?o de descontinuidade microestrutural no a?o, chamada de ZTA (zona termicamente afetada pelo calor). Neste estudo, diferentes rotas de tratamentos t?rmicos foram investigadas com o objetivo de eliminar a ZTA e preservar as caracter?sticas originais do substrato e do revestimento.The application of C-Mn steel pipe in the oil & gas industry is quite common since starting of this industry. Even with the great evolution of the metallurgy of this type of steel over the last decades, the challenge is to overcome the corrosion severity caused by sour (H2S, CO2) species present in the petroleum and its derivates. The direct technological solution would be to replace the C-Mn steel by Ni-based superalloys and/or stainless steels. However, the high costs of these materials would make several projects impracticable. In this context, there are several initiatives in order to develop overlay and/or cladding, that means, coatings of C-Mn steels using superalloys and stainless steels. In this work, it was used an overlay deposition of Inconel 625 on the surface of a C-Mn steel using the laser process. A disadvantage of laser deposition, as it is for any deposition melting process, is the formation of a microstructural discontinuity in the steel substrate caused by the thermal cycle (HAZ = heat affected zone). In this study, different heat treatment routes were investigated aiming to eliminate the HAZ preserving the original characteristics of the substrate and of the coating

Experimental and computer thermodynamics evaluations of an Al-Si-Coating on a quenchable steel

Abstract High-strength steels are commonly used in the automobile industry in order to reduce the weight of the vehicles. However, a technical difficulty appears due to the need of hot stamping of the components, which leads to oxidation. Therefore, the application of a coating on the substrate to avoid high-temperature oxidation is used. In this work, experimental analysis and computer thermodynamic calculation were used to describe the phase transformations within an Al-Si coating on a quenchable high strength steel. The Al-Si coating was deposited by hot dipping and its characterization was done using SEM and XRD techniques. Computer thermodynamics calculations were done using the commercial software FactSage using the Calphad methodology. It demonstrated a good relationship between the experimental results and the computer calculations of phase stabilities for the as-deposited condition and after diffusion experiment at 920ºC for 7 minutes, which simulates the thermal cycle of hot stamping of the quenchable steel used