Overview of Inconel718 (N07718) nickel-based deformed high-temperature alloy
Inconel718 (N07718) nickel-based deformed high-temperature alloy
US brand: Inconel718/UNS N07718
French brand: Nc19FeNb
German brand: W.Nr.2.4668/NiCr19Fe19Nb5
ISO gred: NiCr19Nb5Mo3
1. Overview of Inconel718
Inconel718 alloy is a nickel-based high-temperature alloy precipitated and strengthened by body-centered tetragonal " and face-centered cubic ' phases. It has good comprehensive properties in the temperature range of -253~700 degree . The yield strength below 650 degree ranks among the highest deformation temperatures. It ranks first among alloys and has good fatigue resistance, radiation resistance, oxidation resistance, corrosion resistance, as well as good processing performance, welding performance and long-term structural stability. It can manufacture various parts with complex shapes and is used in aerospace, nuclear energy, In the petroleum industry, it has been widely used in the above temperature range.
Another feature of this alloy is that the alloy structure is particularly sensitive to the thermal processing process. By mastering the phase precipitation and dissolution rules in the alloy and the relationship between the structure, process, and properties, reasonable and feasible process procedures can be formulated according to different use requirements. A variety of parts are available to meet different strength levels and usage requirements. The varieties supplied include forgings, forged bars, rolled bars, cold-rolled bars, round cakes, rings, plates, strips, wires, tubes, etc. It can be made into discs, rings, blades, shafts, fasteners and elastic elements, plate structural parts, casings and other parts for long-term use in aviation.
Inconel718 Chemical Composition The chemical composition of this alloy is divided into 3 categories: standard components, high-quality components, and high-purity components, see Table 1-1. High-quality components reduce carbon and increase niobium on the basis of standard components, thereby reducing the amount of niobium carbide, reducing fatigue sources and increasing the amount of strengthening phases, thereby improving fatigue resistance and material strength. At the same time, harmful impurities and gas levels are reduced. High-purity ingredients are based on high-quality standards to reduce the content of sulfur and harmful impurities and improve material purity and comprehensive performance.
Inconel718 alloy used in nuclear energy needs to control the boron content (other elements remain unchanged), and the specific content is determined by negotiation between the supply and demand parties. When ω (B) Less than or equal to 0.002%, in order to distinguish it from the Inconel718 alloy used in the aviation industry, the alloy grade is Inconel718A.
Inconel718 heat treatment system The alloy has different heat treatment systems to control the grain size, control the δ phase morphology, distribution and quantity, so as to obtain different levels of mechanical properties. Alloy heat treatment systems are divided into three categories:
Ⅰ: (1010-1065) degree ±10 degree , 1h, oil cooling, air cooling or water cooling +720 degree ±5 degree , 8h, furnace cooling at 50 degree /h to 620 degree ±5 degree , 8h, air cooling.
The grains of materials treated by this system are coarsened, there is no δ phase in the grain boundaries and within the grains, and there is notch sensitivity, but it is beneficial to improving impact properties and resisting low-temperature hydrogen embrittlement.
Ⅱ: (950-980) degree ±10 degree , 1h, oil cooling, air cooling or water cooling +720 degree ±5 degree , 8h, furnace cooling at 50 degree /h to 620 degree ±5 degree , 8h, air cooling.
III: 720 degree ±5 degree , 8h, furnace cooling at 50 degree /h to 620 degree ±5 degree , 8h, air cooling.
