RU2288295C1 - Method of treatment of articles of complex configuration made from nickel-based dispersion hardening alloys - Google Patents

Abstract

FIELD: metallurgy; manufacture of articles of complex configuration from nickel-based dispersion hardening alloys.

SUBSTANCE: proposed method includes heat treatment for hardening articles, holding them at this temperature, fast cooling in flow of inert gas to temperature of 650-700°C followed by further cooling in immovable inert medium to temperature of 150°C and final cooling in the air. Prior to fast cooling, additional cooling with furnace by 120-150°C is carried out; after heat treatment, articles are subjected to machining for removal of oxides; then, articles are subjected to X-ray test for volume residual stresses; subjected to treatment are articles with equiaxial, oriented or mono-crystalline structure.

EFFECT: enhanced reliability of articles.

1 dwg, 1 tbl

Description

The invention relates to the field of manufacturing products of complex configuration from precipitation hardening alloys, for example, on a nickel base with equiaxed, oriented or single crystal structure, including their heat treatment, and can find application in aircraft engine building, ground turbine aggregate construction, for example, in the manufacture of hollow turbine blades.

A known method of processing hollow turbine blades, including stabilizing annealing in vacuum furnaces according to the VIAM modes (Yu.S. Eliseev, A.G. Boytsov, V.V. Krymov, L.A. Khvorostukhin. Production technology of aircraft engines. - M.: Engineering, 2003. - S.327-329).

Using this method does not provide the required performance of the products due to the low mechanical properties of the alloy.

Closest to the proposed is a method of heat treatment of products from precipitation hardening alloys according to the copyright certificate SU 1765247 A1, C 22 F 1/10, 09/30/1992, 3 pages, which discloses a method for processing products from dispersion hardening alloys on a nickel basis.

In the manufacture of products of complex configuration, for example, hollow cooled turbine blades made of dispersion hardening alloys, heat treatment requires accelerated cooling to form a strengthening γ'-phase after heating under quenching and holding at a given temperature. This process, like thermal cycling, causes significant volumetric stresses arising inside the blade, which can be summed up with surface ones arising after machining to remove oxides, for example, after sandblasting, as well as with operating stresses.

The technical result to which the invention is directed is to increase the reliability of products.

The technical result is achieved by the fact that in the method of processing products of complex configuration from dispersion hardening alloys, for example, on a nickel base, which includes heat treatment with heating the products for quenching, holding at this temperature, accelerated cooling in an inert gas stream to a temperature of 650-700 ° C and further cooling in a stationary inert medium to 150 ° C, and then in air, in contrast to the known one, before cooling is additionally cooled with an oven at 120-150 ° C, and then thermally machining processing is performed to remove oxides and volumetric control of residual stress by X-ray full release, including the products oriented with equiaxed or single crystal structure.

Cooling with a furnace in a heating chamber by 120-150 ° C allows to increase the strength characteristics of products at high temperatures before accelerated cooling.

The mechanical treatment for removing oxides makes it possible to control single crystal blades for the presence of bulk and surface stresses by the X-ray method. Measurement of stresses on the surface of parts with equiaxed, oriented or single-crystal structure by the X-ray method is possible after machining to remove oxides due to the rotation of the blocks of fine crystalline structure from plastic deformation of the surface layer. Confirmation of the process of formation of a pseudo-polycrystalline structure is the appearance on the surface of a single crystal of a fine-crystalline structure after heat treatment following mechanical treatment.

The control of volume residual stresses makes it possible to determine the possibility of the appearance of internal and external discontinuities and in general the suitability of the obtained products for operation.

The method is as follows.

The parts made of precipitation hardening nickel-based alloys are subjected to heat treatment during the manufacturing process, which produce: heating to a temperature of 30-50 ° C above the temperature of complete dissolution of the strengthening γ'-phase in the heating chamber of a two-chamber vacuum furnace, holding at this temperature, cooling with a furnace in the heating chamber at 120-150 ° C, accelerated cooling in an inert gas stream in the cooling chamber to a temperature of 650-700 ° C and cooling in a stationary inert medium to a temperature of 150 ° C and then in air.

Then the products are machined to remove oxides, for example, in a sandblasting apparatus with regulated particle diameters, nozzle diameters and outlet pressures.

After that, the products are sampled for the presence of volumetric and surface residual stresses by the X-ray method of complete release, which consists in the fact that the selected one is installed on the goniometer of an X-ray diffractometer to irradiate the space against the hollow area, the total residual stresses (surface and volumetric) are measured, then the irradiated area is released electroerosive method, repeat the measurement of residual surface stresses and determine volumetric stresses by algebraic a first subtraction result from the second.

The cooling channel, together with the walls, the back and the trough, is a classic beam with two supports (drawing), which is affected by stresses that tend to tear it away from the supports, i.e. from the jumpers between the back and the trough, carrying one of the main power loads during the operation of the engine blades. Firstly, the voltages σ _vol (table 1) act on the radius R (arising from insufficiently slow cooling during heat treatment; Second - voltage induced mechanically, such as by sandblasting σ _dressings, they have a negative sign in the workpiece surface, and a radius R, they change its sign reversed (+), and then during engine operation the walls are heated from outside and cooling the inside - this is the third component of the stresses σ _t arising from the heating of the blades, and the fourth component of σ _p is the stress from centrifugal loads and from the action of the gas stream. Therefore, a selective X-ray control of residual stresses (surface and volumetric) is proposed by the method of complete release with opening the cavity of the blade and metallographic examination of the radius of the transition from the wall of the blade to the jumper, which determines the first two components of the stresses and the engine warms up at low speeds to reduce the third and initial effects of the fourth.

The proposed X-ray method of complete release in comparison with the method of load cells recommended by CIAM for parts of complex configuration, i.e. for hollow cooled turbine blades, it is more local and allows to separate residual stresses into surface and bulk, and after machining it is possible to determine residual stresses in blades with equiaxed oriented and single-crystal structures.

In the presence of residual stresses above established standards, a decision is made on the suitability of the entire batch of products.

Table 1 - Results of measurements of residual stresses σ _sum σ _over | σ _sum | - | σ _over | σ _about σ _IR + σ _IIR one +10 -47 | +10 | - | -47 | +57 + 57 + 47 = + 114 2 -5 -55 | -5 | - | -55 | +50 + 50 + 55- + 105 3 0 -twenty | 0 | - | -20 | +20 + 20 ++ 20 = + 40 four -5 -27 | -5 | - | -27 | +22 + 22 + 27 = + 49

1, 2 - measurements of residual stresses before changes in the technological process, and 3, 4 - after;

σ _IR is the first component in the radius R;

σ _IIR is the second component in the radius R.

Claims (1)

A method of processing products of complex configuration from precipitation hardening nickel-based alloys, including heat treatment with heating the products for quenching, holding at this temperature, accelerated cooling in an inert gas stream to a temperature of 650-700 ° C and further cooling in a stationary inert medium to 150 ° C, and then in air, characterized in that before accelerated cooling, cooling is additionally carried out with a furnace at 120-150 ° C, and after heat treatment, mechanical processing is carried out to remove oxide fishing and control of volumetric residual stresses by the X-ray method of complete release, while processing products with equiaxial, oriented or single-crystal structure.