How to process Inconel 718?

Inconel 718 is a Fe-Ni-Cr-based precipitation hardening deformation superalloy with good overall performance. The long-term use temperature range is -253~650℃, the short-term use temperature is 800℃, and it has high strength, good toughness and good toughness below 650℃. It is resistant to oxidation and corrosion in both high and low temperature environments. The alloy has good processing performance, welding performance and long-term structural stability, and can manufacture various parts with complex shapes, including rods, plates, tubes, ribbons, wires, etc. Inconel 718 is suitable for the production of rings, blades, fasteners and structural parts in gas turbines, rocket engines, atomic reactors and petrochemical industries in aviation and aerospace.

Similar grades of Inconel 718:

Inconel718 executive standard:

DIN, UNS, ASTM, GB/T14992, AMS, ASME

Inconel 718 chemical composition:

Inconel 718 main specifications: 

cold rolled sheet 4mm-50mm, hot rolled plate 4mm-14mm, hot rolled rod 15mm-100mm, forged rod 100mm-350mm, hot drawn rod 8mm-45mm, band 0.8mm-10mm, tube 10mm-60mm

Inconel 718 physical properties: 

density ρ=8.24g/cm3, melting temperature range 1260～1320℃

Processing considerations：

The processing and heat treatment of Inconel 718's pipes, bars, forgings, pipe fittings, etc. are difficult to process in the field of mechanical processing. The following are the precautions:

★Preheating and heating: W.Nr.2.4668 materials must be surface cleaned during the preheating and heating process to keep the metal surface clean. If the heating environment contains sulfur, phosphorus, lead or other low melting point metals, the nickel alloy material 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 accurate 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.

★Hot and cold processing: The suitable hot processing temperature for this nickel alloy is 1120-900℃, and the cooling method is water quenching or other rapid cooling methods. After hot processing, the metal material should be annealed in time to ensure the best mechanical properties. During hot processing, the material should be heated to the upper limit of the processing temperature. In order to ensure plasticity during processing, the final processing temperature when the deformation reaches 20% should not be lower than 960°C. Cold working should be carried out after solution treatment, and the work hardening rate 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.

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

★Cold sanding: The oxide near the weld of UNS N 07718 workpiece is more difficult to remove than stainless steel. It needs to be sanded with a fine sanding belt. Before pickling in a mixed acid of nitric acid and hydrofluoric acid, sandpaper should also be used to remove oxides or Carry out salt bath pretreatment.

★Machining: Machining needs to be carried out after solution treatment, and the work hardening of the material should be considered. Unlike austenitic stainless steel, Alloy718 is suitable for low surface cutting speeds.

★Welding performance: The precipitation hardening type Inconel718 alloy is very suitable for welding, and there is no tendency to crack after welding. Weldability, ease of processing, and high strength are the major advantages of this material. Suitable for arc welding, plasma welding, etc. Before welding, the surface of the material should be clean, free of oil stains, no powder notes, etc., and the bright metal should be polished within 25mm around the weld.

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