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Types of Corrosion in the Offshore Environment
Published in Karan Sotoodeh, Coating Application for Piping, Valves and Actuators in Offshore Oil and Gas Industry, 2023
Carbon and low-alloy steel materials are not considered corrosion-resistant, so for RTJ flanges in carbon and low-alloy steel material, it is common to apply Inconel 625, which is a highly corrosion-resistant material, on the ring grooves to prevent crevice corrosion. The other two types of corrosion, pitting and CLSCC, can occur in grooves such as those on RTJ flange faces. Thus, applying Inconel 625 on flange ring grooves is a very good way to prevent all three types of localized corrosion. Applying Inconel 625 or other nickel alloys to prevent corrosion on a non-corrosion-resistant alloy is known as “cladding.” Inconel 625 is typically clad by weld overlay method in a thickness of 3 mm. Some specifications may require a minimum of two layers of weld overlay on Inconel 625. If the weld overlay is done in sour services, meaning services with a considerable amount of hydrogen sulfide (H2S), then the hardness of the Inconel 625 should be limited to 35 HRC (Rockwell C) according to ISO 15156 and NACE MR 0175 requirements. These standards address material selection for use in H2S -containing services in the oil and gas industry. Inconel 625 contains more than 50% nickel, between 20% and 23% chromium and between 8% and 10% molybdenum. This nickel alloy provides high corrosion resistance against various types of corrosion, such as crevice, pitting, hydrogen sulfide and carbon dioxide. The other important properties of Inconel 625 are its high strength and very good weldability and ductility. The strength of Inconel 625 is not of benefit for weld overlay application, because weld overlay is not performed for improving mechanical strength.
The Research of Manufacturing for HL-2M Vacuum Vessel
Published in Fusion Science and Technology, 2023
Hong Ran, Jilai Hou, Binbin Song, Yuncong Huang, Dangshen Zhang, Qinwei Yang, Le Tang, Xiaoqiang Wu, Zen Cao, Lijun Cai
The HL-2M VV has a double-wall complex structure with D-shaped cross section. Its manufacturing is feasible through experiences summarized from a long way of R&D and the actual manufacturing. The main results are as follows: Inconel 625 is a nickel-chromium alloy. As it has higher strength and worse molten pool fluidity than 316L, its manufacturing difficulty is greater, especially the weldability. Hot cracks, air holes, and incomplete penetration are likelier to occur than with 316L. A reasonable welding process and corresponding methods shall be taken to avoid these defects.For the thin-walled structures, it is found that welded joint qualities with acceptable conditions can be obtained by the TIG welding method. Welding distortion can be diminished through small heat input, fast welding, and powerful cooling.A 3D cold forming process is used in a hyperboloid thin plate. The frame die can save grinding time and cost and has high production efficiency.Fixture design is very important. Proper fixture is helpful to restrain welding deformation and assembly.
Prediction and optimization of work-piece temperature during 2.5-D milling of Inconel 625 using regression and Genetic Algorithm
Published in Cogent Engineering, 2020
Satish Kumar, Pankaj Chandna, Gian Bhushan
In the field of machining, 2.5D is a term often referred to as a part having multiple flat features with variable depth. 2.5D end milling is among the largely commercially trendy technologies used in machining of different products like aerospace, dies, marine and low rigidity thin-sectioned components (Kumar, Gupta, & Chandna, 2014). Inconel 625 is a high strength nickel-based superalloy that is broadly used in aerospace, automobile, heat exchanger, combustors, seals, steam generators and nuclear applications. Because of low thermal conductivity, high temperature and high hardness, machining of this alloy is quite difficult (Parida & Maity, 2018). During the milling process, the tool work-piece interface generates extreme friction and intense cutting forces. The energy consumed during the cutting is converted into the heat which is further divided among the work-piece, tool & chip (Vallavi, Gandhi, & Velmurugan, 2006). Because of the lower thermal conductivity of the work-piece and the extreme heat generation, thermal expansion causes the deformation in the local area. Nickel-based superalloy work-piece commonly faces such types of challenges in the industries (Cai, Qin, Li, An, & Chen, 2014).
Consolidation mechanism, microstructural evolution and corrosion resistance of Inconel 625 coatings
Published in Surface Engineering, 2021
Eyitayo Olatunde Olakanmi, Kinsman Malikongwa, Sipiwe Trinity Nyadongo, Shaik Hoosain, Sisa Lesley Pityana
Laser cladding (LC) is employed in improving the surfaces of engineering components against wear, corrosion and oxidation problems. It offers unique advantages such as a limited heat-affected zone (HAZ), smaller stress deformation, lower weld dilution and good metallurgical bonding between the coating and the substrate [1–3] over conventional processes such as vacuum plasma spray (VPS), arc welding and high velocity oxy-flame (HVOF). These conventional processes are associated with distortion of engineering parts and formation of intermetallic phases which induce poor mechanical performance and residual stresses [4]. Inconel 625, a nickel-based super alloy consisting of nickel-chromium-molybdenum, derives its excellent mechanical properties from the solution hardening influence of niobium and molybdenum in an austenitic face-centered crystal (FCC) γ matrix. Annealing the alloy between 550 and 580°C increases its strength due to precipitation of fine metastable phase γ” Ni3Nb [5,6]. It is also characterized by high temperature strength and excellent corrosion resistance in different corrosive media. According to Paul et al. [5] and Dinda et al. [6], chromium and nickel are resistant to oxidising atmospheres whereas molybdenum and nickel counteract the influence of reducing environments. Chromium prevents corrosion by forming a layer of Cr2O3, and molybdenum provides resistance to crevice and pitting corrosion [6]. Inconel 625 also has good ductility which accounts for its non-susceptibility to cracking upon solidification and contraction after welding [7,8]. These properties make Inconel 625 an essential alloy for applications in the marine, aerospace and petrol-chemical industries.