Incoloy Alloy 825

Chemical Composition

Incoloy 825 high temperature alloy is mainly composed of nickel, chromium, copper, molybdenum and iron, but also contains phosphorus, sulfur, carbon, manganese and other trace elements. The nickel content of 38 - 46%, chromium content of 19.5 - 23.5%, copper content of 1.5 - 3%, molybdenum content of 2.5 - 3.5%, iron as a residual play a role in balancing the elements to ensure that the overall composition of the alloy, while providing a certain degree of strength and toughness of the alloy.

Performance characteristics

Corrosion resistance

A variety of media resistance: Incoloy 825 alloy in a variety of media corrosion resistance performance is excellent, able to resist sulfuric acid, phosphoric acid, nitric acid, hydrofluoric acid, hydrochloric acid, organic acids and other corrosive substances, as well as sodium hydroxide, potassium hydroxide and other alkali metal erosion.

Application in complex environments: in the nuclear combustion dissolver such as the need to simultaneously deal with sulfuric acid, nitric acid and sodium hydroxide and other corrosive media in complex environments, the alloy can also rely on its excellent corrosion resistance to do the job.

High temperature stability

Can maintain stable performance in high temperature environment, the applicable temperature is generally not more than 550 ℃, in this temperature range of its structure and performance stability, can withstand high temperatures and high stress.

Toughness

At room temperature and high temperature can maintain good toughness, in terms of mechanical properties of the elongation can usually reach 30% or so, showing good plasticity and ductility, can be a large deformation in the force without fracture.

Molding and weldability

Has good molding and welding, whether cold or hot processing, can maintain good performance and stability, which makes it easy to deal with in a variety of processing operations.

Physical Properties

Melting point range between 1370 - 1400℃.

Mechanical properties

Tensile strength of about 550MPa, able to withstand large tensile loads without fracture.

Brinell hardness (Brinell hardness) is about 160. indicating a certain degree of hardness and wear resistance.

Heat treatment

Annealing and solution treatment: Annealing and solution treatment can be carried out in the temperature range of 1000 - 1150°C. Solution treatment is usually carried out in the temperature range of 980 - 1140°C with heating and holding, followed by rapid cooling. Solution treatments increase the plasticity and toughness of the alloy while reducing the hardness and strength.

Sink Hardening: Can be used to increase the hardness and strength of Incoloy 825 alloy. During sink quenching treatment, the alloy is heated and held at a higher temperature and then rapidly cooled, causing changes in the lattice structure of the alloy and the formation of reinforcing phases.

Quenching and tempering treatment: This is a further treatment after the immersion quenching treatment and is designed to reduce the brittleness of the alloy and increase the toughness. In the process of quenching and tempering treatment, the alloy is firstly subjected to immersion quenching treatment, and then tempered and annealed, so that the alloy reaches the ideal balance of strength and toughness.

Machining Processes

Hot working:

Suitable hot working temperatures are 1150 - 900°C. Cooling may be by water quenching or rapid air cooling.

For hot working, the workpiece can be fed directly into a furnace that has been brought to temperature. After the furnace has come to temperature, the material is held for 60 minutes per 100 mm thickness. Immediately after the holding time to the specified time, out of the furnace, in the specified temperature range processing. If the temperature of the metal drops below the minimum processing temperature, it should be heated again. After hot working, it should be annealed promptly to ensure that the corrosion resistance and suitable crystal structure are obtained.

Cold working:

Should be carried out after solution treatment, work hardening rate and austenitic stainless steel close, so the processing equipment should be adjusted accordingly.

There should be an intermediate annealing process when the amount of cold working is large. When the final cold deformation is greater than 15% of the final stabilization process is required.

Cutting: relatively difficult, because it has high hardness and plastic deformation resistance. When cutting process is carried out, it is necessary to use suitable tools and cutting parameters to minimize cutting forces and wear.

Thermal compression: Thermal compression can be performed within a certain temperature range to improve its plasticity and machinability. In the hot compression process, the temperature, deformation rate and stress need to be controlled to obtain the desired deformation and microstructure.

Hot Extrusion: It is a commonly used hot processing method to prepare rods, tubes and profiles of Incoloy 825 alloy. In the process of hot extrusion, the extrusion temperature, extrusion speed and extrusion ratio need to be controlled to obtain the desired shape and properties.

Hot Forging: can be used to prepare large and complex shaped parts of Incoloy 825 alloy. In the hot forging process, the forging temperature, forging speed and stress need to be controlled to obtain the desired shape and properties.