The method of complex hardening

 

The invention relates to mechanical engineering and can be used to improve the fatigue characteristics of parts from titanium alloys, in particular of compressor blades of GTE made of wrought titanium alloys. A method for complex hardening of parts from titanium alloys, including shot blasting with subsequent thermal treatment, while blasting treatment on the treated area of the sheet exercise speeds of 30-70 m/C for 30-60 s, and as a heat treatment to spend for 3-6 hours at a temperature of not lower operational and not higher than 450°C. In preferred embodiments of the invention blasting may be made of glass and/or metal beads with a diameter of 50-400 μm, the temperature of the leave is 300-450°C, and as parts of titanium alloys using blades of the compressor turbine engines. The invention improves the fatigue limit due to the complex hardening of titanium alloys. 2 C.p. f-crystals, 1 tab., 2 Il.

The invention relates to mechanical engineering and can be used to improve the fatigue characteristics of parts from titanium alloys, chastnostb>Known methods of surface plastic deformation of metal parts and glass shot (balls), dispersed by compressed air, liquid or rotating blades blast wheel. TTD can improve the fatigue detail by pointing in a thin surface layer of residual compression stress, work hardening, and "healing" (smoothing, rounding) surface microdefects (verbov, scratches, pores, etc.) (see Odintsov L., Hardening and finishing details by surface plastic deformation. The Handbook. - M.: Mashinostroenie, 1987, S. 242-250).

The efficacy of the DPP is limited not only by an elastic-plastic state of the surface layer parts that carry the features of the previous treatments (so-called technological "heredity"), but the presence of the design stress concentrators (radii of the edges of the blades). These features do not allow a proper use of the energy possibilities of surface hardening processes, because it can lead to proclaiming edges of the blades.

It was found that after TTD hardened surfaces have a high energy and will is the R loads can diffuse into the details, lowering resistance to the emergence of cracks. These factors can lead not only to lower values of durability, but the fatigue limit of the details.

The prior art method of heat treatment of titanium alloys products, including mechanical treatment in air or protective environments, the subsequent low-temperature annealing at 450-510°C for 5-10 h with subsequent cooling and polishing (SU 411154, IPC-2 C 22 F 1/18, 15.01.1974, formula).

The disadvantages of this method include the fact that the annealing allows only to neutralize the negative effects of mechanical processing, but to create an optimal controlled quality of the surface layer can only superficial hardening, the use of which in the author's evidence is missing.

Closest to the claimed method is a method of machining of titanium alloys, including shot blasting the beads with a diameter of 160-200 μm at a pressure of 2.5-3 ATM for 5-6 min, followed by annealing at 550±10°C for 4-7 min (SU 872595, IPC-3 C 22 F 1/18, 15.10.1981, formula).

The disadvantage of this method is that the residual compressive stress and the work hardening that occurs when shot peened on the ProcName, since the maximum allowable temperature, which is an effect of hardening450°C. Further, the exposure time of the annealing (5-7 min) is not sufficient to neutralize the adsorbed oxygen on the surface, diffusing into it, and thereby causing an accelerated growth of fatigue cracks.

The objective of the invention is to increase the fatigue limit of parts from titanium alloys.

The objective of the invention is achieved by the implementation of the method of complex hardening of parts from titanium alloys, including shot blasting with subsequent thermal treatment, according to the invention blasting treatment on the treated area of the sheet exercise speeds of 30-70 m/C for 30-60 s, and as a heat treatment to spend for 3-6 hours at a temperature of not lower operational and not higher than 450°C.

In a preferred embodiment, the method of shot blasting conducting glass and/or metal beads with a diameter of 50-400 μm.

In a preferred embodiment of the invention, the temperature of the leave is 300-450°C.

In a preferred variant of the invention, the parts made of titanium alloys useddock on the treated area of the sheet i.e. at the site equal to the diameter of the torch fraction. After processing one portion of the items within 30-60 spend processing the next unprocessed area details within 30-60 and so until then, will not be processed until the entire part. This is due to the fact that the workpiece can be of different shapes and sizes and sometimes it is not possible to process the entire part at the same time because of insufficient diameter of the torch fraction.

Integrated hardening, reducing the value of the residual compression stress and work hardening by 25-30%, formed after injection at the same time, reduces their variance, which is based on technological "inheritance" from 25-100% 30-40%, i.e., along with the decline, is aligned over the entire surface detail, which is especially important for the design of the hub, because it prevents them from proclip, as well as the technological hub, removing the sharp transition of the stress values. In addition, the reduction and equalization of stresses leads to a decrease leashes detail, ensuring its value within the specified tolerance.

Combined hardening provides a "compacted" and reasonably "oriented" homogeneous structure with fine grain, EF is ska adsorbed oxygen is bound in stable chemical compound (Tio2), not allowing it to diffuse into the surface. Which reduces the likelihood of subsurface cracks.

The following examples illustrate, but not limit application of the claimed method.

Effectiveness of complex hardening was carried out on the blades of titanium alloy VTZ-1, made in accordance with OST1 90002-86, the minimum radius of the edges of which was equal to Rto=0,2-0,22 mm

The following table shows the modes pneumogastric processing (DTP) and the subsequent tempering blades.

In Fig.1 and 2 presents the results of the experiment, allowing to evaluate the effectiveness of an integrated hardening.

The experiment showed that the padding on modes 1 and 2 gives the greatest effect compared to less intensive modes. When changing modes in the direction of increasing their energy parameters (modes 1.1 and 2.1) has a drop fatigue limit compared to modes 1 and 2 with 460-480 MPa to 430-440 MPa.

Integrated reinforcement profiles 1.3 and 2.3) allows to obtain the highest values of the fatigue limit of 540 MPa, which corresponds to a residual compression stress value of 200-300 MPa and a depth of 40-60 microns.

The choice of modes blasting simplified in order to obtain their most rational values for specific sections of the radii of the edges of GTE blades.

Modes hardening adjusted towards reducing their energy level because of the tendency of higher values of the quality parameters to relax more intensively and, thereby, reduce the hardening effect.

When assigning temperature must assume that it must be not lower operational and not to exceed 450°C, because above this value the hardening effect disappears (according to mode 1.4 increasing the tempering temperature up to 450°C caused a decrease of the fatigue limit to 510 MPa).

Claims

1. The method of complex hardening of parts from titanium alloys, including shot blasting with subsequent heat treatment, characterized in that the blasting treatment on the treated area of the sheet exercise speeds of 30-70 m/C for 30-60 s, and as a heat treatment to spend for 3-6 hours at a temperature of not lower operational and not higher than 450°C.

2. The method according to p. 1, characterized in that the blasting treatment is carried out, the glass and/or metal beads with a diameter of 50-400 μm.

3. The method according to p. 1 or 2, characterized in that t is of titanium alloys using blades of the compressor turbine engines.

 

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SUBSTANCE: invention relates to valve of internal combustion engine, method of its manufacture and heat-resistant titanium alloy used for manufacture of valve consisting of following components, mass %: aluminum 7.5-12.5; molybdenum 1.6-2.6; zirconium 1.4-2.4; silicon 0.1-0.2' yttrium 0.005-0.1; titanium - the rest. It has α+α2+β phase composition with intermetallide α2 phase on Ti3Al base dispersed in α phase. Proposed method includes forming of valve from cylindrical blank by deformation machining with preliminary heating and subsequent heat treatment. Preliminary heating of part of blank related to rod done to temperature 5-20oC lower than temperature of complete polymorphic transformation of alloy, and its deformation machining is carrying out by wedge cross rolling. Deformation machining of part of blank related to head is done by forging with preliminary heating to temperature 5-50oC higher than temperature of complete polymorphic transformation of alloy corresponding to beginning of forging, and forging is finished at temperature lower than complete polymorphic transformation of alloy to form plate head of valve and transition section provided smooth changing of head into rod. Invention provides designing of valve, method of its manufacture and heat-resistant alloy used in manufacture of valve making it possible to operate valve within operating temperature range owing to increased long-term strength and creep resistant of valve head material and increased strength, modulus of elasticity and hardness of valve rod material.

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