Nickel base alloy is a kind of alloy with high strength and certain anti-oxidation and corrosion ability at 650 ~ 1000 ℃. According to the main properties, it is divided into nickel base heat-resistant alloy, nickel base corrosion-resistant alloy, nickel base wear-resistant alloy, nickel base alloy and nickel base shape memory alloy.

According to different matrix, superalloys can be divided into iron base superalloys, nickel base superalloys and cobalt base superalloys. Nickel base superalloy is called nickel base alloy for short.

The representative materials of nickel base alloys are: 1. Incoloy alloy, such as Incoloy800, the main components are; 32Ni-21Cr-Ti,Al； It belongs to heat-resistant alloy; 2. Inconel alloys, such as inconel600, are mainly composed of:; 73Ni-15Cr-Ti,Al； It belongs to heat-resistant alloy; 3. Hastelloy alloy, i.e. Hastelloy alloy, such as Hastelloy C-276, is mainly composed of; 56Ni-16Cr-16Mo-4W； It belongs to corrosion-resistant alloy; 4. Monel alloy, namely Monel alloy, such as Monel 400, is mainly composed of; 65Ni-34Cu； It belongs to corrosion-resistant alloy;

The main alloy elements are chromium, tungsten, molybdenum, cobalt, aluminum, titanium, boron, zirconium, etc. Among them, Cr, AI and other elements mainly play the role of oxidation resistance, while other elements play the role of solid solution strengthening, precipitation strengthening and grain boundary strengthening.

It has high strength and certain anti-oxidation and corrosion capacity under high temperature of 650 ~ 1000 ℃. Due to its high enough high temperature strength and anti-oxidation and corrosion capacity, it is commonly used to manufacture high-temperature parts of aero-engine blades and rocket engines, nuclear reactors and energy conversion equipment.

Nickel base superalloys are widely used. The main reasons are as follows: firstly, more alloying elements can be dissolved in nickel base alloys, and good structural stability can be maintained; Second, it can form coherent ordered a3b type Intermetallics γ [ni3 (al, Ti)] phase is used as strengthening phase to effectively strengthen the alloy and obtain higher high-temperature strength than iron-based superalloy and cobalt based superalloy; Third, nickel base alloys containing chromium have better oxidation resistance and gas corrosion resistance than iron base superalloys. Nickel base alloys contain more than ten kinds of elements, of which CR mainly plays the role of oxidation and corrosion resistance, and other elements mainly play the role of strengthening. According to their strengthening ways, they can be divided into: solid solution strengthening elements, such as tungsten, molybdenum, cobalt, chromium and vanadium; Precipitation strengthening elements such as aluminum, titanium, niobium and tantalum; Grain boundary strengthening elements, such as boron, zirconium, magnesium and rare earth elements.

Nickel base superalloys can be divided into solid solution strengthening type and precipitation strengthening type.

Production process:

Smelting: in order to obtain more pure and purified molten steel, reduce the content of gas and harmful elements; At the same time, due to the existence of oxidizable elements such as Al and Ti in some alloys, non vacuum smelting is difficult to control; In order to obtain better thermoplasticity, nickel base heat-resistant alloys are usually melted in vacuum induction furnace, or even produced by vacuum induction smelting plus vacuum consumable furnace or electroslag furnace remelting.

Deformation: forging and rolling processes are adopted. For alloys with poor thermoplasticity, extrusion and rolling after blank opening or direct extrusion process with mild steel (or stainless steel) sheath is even adopted. The purpose of deformation is to break the casting structure and optimize the microstructure.

Casting: the master alloy is usually melted in a vacuum induction furnace to ensure the composition and control the content of gas and impurities, and the parts are made by vacuum Remelting Casting method.

Heat treatment: deformed alloys and some cast alloys need heat treatment, including solution treatment, intermediate treatment and aging treatment. Taking udmet 500 alloy as an example, its heat treatment system is divided into four stages: solution treatment, 1175 ℃, 2 hours, air cooling; Intermediate treatment, 1080 ℃, 4 hours, air cooling; One time aging treatment, 843 ℃, 24 hours, air cooling; Secondary aging treatment, 760 ℃, 16 hours, air cooling. To obtain the required organizational state and good comprehensive performance.