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7 Steps of Inconel 718 Processing and Heat Treatment

Views:68     Author:RONSCO     Publish Time: 2021-06-10      Origin:RONSCO

Inconel 718 is a precipitation hardening nickel-chromium-iron alloy containing niobium and molybdenum. It has high strength, good toughness and corrosion resistance in high and low temperature environments below 650°C. The state can be solid solution treatment or precipitation hardening state. Inconel 718 is a difficult-to-process material in the field of mechanical processing.


Warm up


The surface of the workpiece must be cleaned before and during the heating process to keep the surface clean. If the heating environment contains sulfur, phosphorus, lead or other low melting point metals, Inconel 718 alloy will become brittle. Impurities come from marking paint, chalk, lubricating oil, water, fuel, etc. The sulfur content of fuel should be low. For example, the impurity content of liquefied gas and natural gas should be less than 0.1%, the sulfur content of city gas should be less than 0.25g/m3, and the sulfur content of petroleum gas should be less than 0.5%.


The heated electric furnace should have a more precise temperature control capability, and the furnace gas must be neutral or weakly alkaline, and fluctuations in the oxidizing and reducing properties of the furnace gas should be avoided.


Thermal processing


The suitable hot working temperature of Inconel 718 alloy is 1120-900℃, and the cooling method can be water quenching or other rapid cooling methods. After hot working, it should be annealed in time to ensure the best performance. The material should be heated to the upper limit of the processing temperature during hot processing. In order to ensure the plasticity during processing, the final processing temperature when the deformation reaches 20% should not be lower than 960°C.


Cold working


Cold working should be carried out after solution treatment. The work hardening rate of Inconel 718 is greater than that of austenitic stainless steel, so the processing equipment should be adjusted accordingly, and there should be an intermediate annealing process during the cold working process.


Heat treatment


Different solution treatment and aging treatment processes will result in different material properties. Due to the low diffusion rate of γ" phase, Inconel 718 alloy can obtain the best mechanical properties through long-term aging treatment.


Polished


The oxide near the weld of Inconel 718 workpiece is more difficult to remove than stainless steel. It needs to be polished with a fine sanding belt. Before pickling in a mixed acid of nitric acid and hydrofluoric acid, the oxide should be removed with sandpaper or a salt bath is required. deal with.


Machining


The machining of Inconel 718 needs to be carried out after solution treatment, and the work hardening of the material should be considered. Unlike austenitic stainless steel, Inconel 718 is suitable for low surface cutting speeds.


Welding


The precipitation hardening type Inconel 718 is very suitable for welding and has no tendency to crack after welding. Weldability, ease of processing, and high strength are the major advantages of this material.


Inconel 718 is suitable for arc welding, plasma welding, etc. Before welding, the surface of the material should be clean, free of oil, powder, etc., and the bright metal should be polished within 25mm of the weld.


Inconel 718 recommended welding materials:

GTAW/GMAW

Nicrofer S 5219

W.-Nr. 2.4667

SG-NiCr19NbMoTi

AWS A 5.14 ERNiFeCr-2

BS 2901 Part 5: NA 51


PH Stainless Steel
17-4PH
17-7PH
15-5PH
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