China brand: GH738 nickel-base superalloy.

American brand: Waspaloy

French brand: NC20K 14

Overview of 1.GH738 nickel-base superalloy:

GH738 is a Ni-based superalloy precipitation hardened by γ′ phase, which has good gas corrosion resistance, high yield strength and fatigue performance, good process plasticity and stable microstructure. Widely used in aero-engine rotating parts, the service temperature is not higher than 865438 05℃. It can produce cold-rolled and hot-rolled plates, pipes, strips, wires and forgings, castings and fasteners.

1, GH738 material brand: GH738

2. Similar brands of 2.GH738: Waspaloy (USA), NC20K 14 (France).

3, GH738 material technical standards:

4. Chemical composition of 4.GH738:? See table 1- 1.

Note: Trace impurities are ω(Pb)≤0.00 1%, ω(As)≤0.0025%, ω(Sn)≤0.00 12%, ω(Sb)≤0.0025% and ω (Bi) ≤ 0.000. ?

5. Heat treatment system of 5.GH738: 1080℃ 10℃, 4h, air cooling +840℃, 24h, air cooling +760℃, 16h, air cooling.

6. Variety specification and supply status of 6.GH738: It can produce bars, profiles, forging blanks, rings, thick plates, thin plates, strips, pipes, wires, sand castings, precision castings and fasteners. , usually delivered without heat treatment, and the board is delivered after solution treatment.

7. smelting and casting process of 7.GH738:? Vacuum induction melting and vacuum arc remelting processes are adopted.

8. General situation and special requirements of 8.GH738 application: The alloy is widely used in aero-engines and gas turbines abroad, mainly used as rotating parts such as turbine blades and disks, with mature experience. Because of the high cobalt content, this alloy is rarely used in China.

Second, physical and chemical properties of GH738:

Thermal characteristics of 1 and GH738;

The melting temperature range of (1) and GH738: 1330 ~ 1360℃.

(GH738 thermal conductivity: see table 2- 1.

2. Density of 2.GH738: ρ=8.22g/cm3.

3. Electrical characteristics of 3.GH738:?

4. Magnetism of 4.GH738: The alloy has no magnetism. ?

5. Chemical properties of 5.GH738:

Oxidation resistance of (1) and GH738: See Table 2-4 for the oxidation rate of the alloy after100h in air.

(Corrosion resistance of GH738: The alloy has good salt spray corrosion resistance.

Four. Tissue structure of GH738:

1 and GH738 phase transition temperature: the dissolution temperature of γ′ phase in the alloy is 980 ~ 1050℃, the initial precipitation temperature from the matrix is 630℃, and the precipitation peak temperature is 800℃. The initial precipitation temperature of M23C6 carbide phase in the alloy is 700℃, and the complete dissolution temperature is 1020℃.

2.GH738 time-temperature-microstructure transition curve:

3. Microstructure of 3.GH738 alloy;

After standard heat treatment, except for the austenite matrix, the number of γ′ phases in the alloy aged at 650℃ and 730℃ for 3000h has no obvious change, with about 3% and 1% of supplementary precipitation respectively, and the size of γ′ phases has increased from 146nm to 196nm and/kloc-respectively. When carbide MC is transformed into M23C6, the total amount of carbide increases slightly, from 0.5% of the total matrix before aging to 0.76% and 0.78%. No new phase is precipitated during long-term aging, and the structure is stable.

Technical properties and requirements of verb GH738 (abbreviation of verb);

Molding properties of 1 and GH738;

The plasticity diagrams of (1) and GH738 alloys are shown in figure 5- 1.

(See Figure 5-2 for the recrystallization diagram of GH738 alloy.

(3) GH738 This alloy has good hot working plasticity and is a nickel-based superalloy with good formability. The heating temperature of forging cogging is1150 ~1170℃, the suitable hot working temperature is1040 ~1170℃, and the final forging temperature is not lower than/kloc. The forging temperature of turbine blades is usually between1070 ~110℃, and the minimum deformation of die forging should be greater than 25%. Hot working at high temperature (65,438+065,438+080℃) with small deformation (about 65,438+00%) should be avoided. At this time, a continuous MC-type carbide film may be formed on the grain boundary, resulting in notch sensitivity. At low temperature (980 ~ 1080℃), MC carbide film is rarely formed on the grain boundary, only discontinuous M23C6 carbide. After heat treatment, 4 ~ 5 grades of uniform grains can be obtained, which has good comprehensive properties.

2. Heat treatment process of 2.GH738 parts:? During the heat treatment of parts, attention should be paid to prevent the surface elements of parts from being exhausted, and the heating should be uniform.

3, GH738 surface treatment process:? When the alloy is used as rotating parts such as turbine blades, turbine disks, etc., in order to improve the fatigue performance, argon protection stress relief annealing and shot peening treatment are carried out. In order to improve the gas corrosion resistance and thermal fatigue resistance of turbine blades, diffusion aluminizing treatment can be carried out.

Six, GH738 varieties specifications and supply situation:

1. Variety classification: Special alloy can produce GH738 seamless pipe, GH738 steel plate, GH738 round steel, GH738 forging, GH738 flange, GH738 circular ring, GH738 welded pipe, GH738 steel strip, GH738 wire rod and GH738 supporting welding material of various specifications.

2, delivery status: seamless pipe: solid solution+acid white, the length can be determined; Plate: solid solution, pickling and trimming; Welded pipe: solid solution acid white +RT% flaw detection, forging: annealing+turning; Bar forging and rolling, surface polishing or turning; The strip is output after cold rolling, solution softening and descaling; The wire is delivered in the state of solution pickling, disc shape or straight bar, and the solution straight bar is finely polished.