Repair method for titanium alloy blade of aircraft engine compressor
Technical Field
The invention belongs to the technical field of welding, and particularly relates to a repair method for a titanium alloy blade of an aircraft engine compressor.
Background
The compressor blade is one of key components of an aircraft engine and is positioned at the air inlet end of the engine. In the service process, the blade profile size is lost due to foreign object impact, airflow scouring, friction and abrasion and the like. The damaged compressor blades are welded, repaired and processed to restore the overall dimension of the blades, so that the replacement number of new blades can be reduced, the maintenance period is shortened, and the service cost of the whole service life of the engine is reduced.
Because the sealing ring, the sealing gasket, the lubricant and the like are remained on the surface of the compressor blade after service and an oxide film exists on the surface, the welding quality is influenced if the compressor blade is not thoroughly cleaned. Because the engine blade bears huge alternating stress in the service process, the requirement on the surface integrity of the repaired blade is high, and the traditional method for performing surface vibration finishing and shot blasting reinforcement after machining has more processes and higher cost.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for repairing a titanium alloy blade of an aircraft engine compressor, which adopts a low-heat-input microbeam plasma arc welding process and realizes a complex motion track of a three-dimensional space by driving a welding gun through a multi-axis linkage robot; the precise forming and repairing of the compressor blade can be realized, the welding repair area has no cracks and impurities, the welding line is full, and a certain machining allowance is reserved.
The technical problem to be solved by the invention is realized by the following technical scheme:
a method for repairing a titanium alloy blade of an aircraft engine compressor is characterized by comprising the following steps: the repairing method comprises the following steps:
step 1: cleaning the titanium alloy compressor blade before welding;
step 2: processing a part to be welded of a titanium alloy compressor blade;
and step 3: carrying out nondestructive testing on the titanium alloy compressor blade;
and 4, step 4: carrying out micro-plasma arc welding on the titanium alloy compressor blade;
and 5: carrying out postweld heat treatment on the titanium alloy compressor blade;
step 6: carrying out electrolytic machining on a titanium alloy compressor blade welding area;
and 7: and carrying out nondestructive testing on the welding repair blade of the titanium alloy compressor.
Moreover, the specific operations of cleaning before welding in the step 1 are as follows: primarily cleaning the blade by using an acetone organic solvent, and thoroughly cleaning a sealing ring, a sealing gasket and a lubricant which are remained on the blade; cleaning an oxide film on the surface of a blade by pickling, wherein the pickling temperature is 30-60 ℃, the pickling time is 1-10 min, the pickling corrosion amount is 0.02mm, and the formula of pickling solution used for pickling is as follows:
10 to 20 percent of nitric acid
50 to 60 percent of hydrofluoric acid
20-40% of distilled water.
And 2, after the damaged part of the compressor blade in the step 2 is cut by a water jet cutter, polishing the cut surface from coarse to fine until the roughness is superior to Ra0.1-0.05.
And in addition, the compressor blade in the step 3 is subjected to crack inspection according to a fluorescent liquid penetration inspection standard.
In addition, the compressor blade in the step 4 is clamped by a flexible clamping mechanism, and the surface to be welded of the damaged blade is required to be 0.5-3.0 mm higher than the chuck; determining the number of weld passes for surfacing repair according to the missing size of the profile of the blade and the surfacing height of each weld joint; setting a welding track as a central line of the surface to be welded, wherein an arc starting position is 0.5-3.0 mm in front of a front edge of the surface to be welded of the blade, an arc receiving position is 0.5-3.0 mm behind a rear edge of the surface to be welded of the blade, and the height of the arc starting/receiving position is 2.0-5.0mm above the surface to be welded of the blade; the welding adopts high-purity argon to construct triple protective atmosphere, the flow of protective gas of a molten pool is 20-40SCFH, an outlet is positioned right above the molten pool and blows towards the molten pool vertically and downwards, the flow of protective gas on the front side of a welding seam is 100-200 SCFH, the outlet is positioned right above the welding seam and blows towards the welding seam vertically and downwards, the flow of protective gas on the back side of the welding seam is 3-10 SCFH, and the outlet is positioned on a blade clamping tool and blows towards the root part of the welding seam laterally; the welding process is as follows:
(1) moving a welding gun to an arc striking position, starting molten pool shielding gas, welding seam front shielding gas and welding seam back shielding gas, staying for 20-50 seconds, and removing air in a welding area to avoid oxygen, nitrogen and hydrogen elements in the air from entering a molten pool to deteriorate the performance of a welding joint;
(2) keeping for 1-10 s after arcing at an arcing position, keeping the welding current at a lower power after plasma arc is stabilized, moving a welding gun to be 2.0-5.0mm right above the front edge of the surface to be welded of the blade under the guidance of a manipulator, and carrying out surfacing welding at a lower power and a larger wire feeding amount to enable the front edge of a surfacing area of the blade to be full and leave enough machining allowance;
(3) the welding gun continues surfacing at a welding heat input amount and a wire feeding speed which are suitable for the width of the welding seam;
(4) starting to reduce welding current at a position 2-10mm away from the rear edge of the blade, improving the wire feeding speed, and moving a welding gun to the arc closing position of the blade under the guidance of a manipulator to avoid the collapse of the rear edge;
(5) closing plasma arcs at arc withdrawing positions, simultaneously drawing back welding wires to be separated from a molten pool, closing protective gas after the temperature of a surfacing area is cooled to be lower than 200 ℃, and finishing first-pass weld surfacing;
(6) the welding process is repeated until the designed number of weld passes is reached.
And performing stress relief heat treatment on the compressor blade in the step 5 in a vacuum or argon atmosphere, wherein the heat treatment temperature is not higher than the phase transition temperature of the titanium alloy.
In addition, the compressor blade in the step 6 removes redundant titanium alloy in a surfacing area through electrolytic machining, a cathode of the electrolytic machining adopts a dispersed hole water outlet mode, and the electrolyte adopts NaCl as the basis of the electrolyte and is added with a complexing agent; the electrolytic voltage is 20V, and the current density is 55-65A/cm2The machining gap is 0.2-1.8 cm, and the machining speed is 0.15-0.20 mm/s.
And moreover, the compressor blade in the step 7 adopts visual appearance detection, X transmission detection and fluorescence penetration detection, and simultaneously detects the relevant sizes of the blade, so that the damaged and repaired area is determined to be complete and clean without undercut and hole defects, the front edge and the rear edge of the repaired area are full in appearance and have no collapse, and the appearance color is silvery white or light golden yellow.
The invention has the advantages and beneficial effects that:
according to the repairing method of the titanium alloy blade of the aircraft engine compressor, a multi-axis linkage robot is adopted to drive a welding gun to realize a complex motion track of a three-dimensional space, the welding process parameters of the upper edges of all the blades are set in a segmented mode by integrating the welding process of the front edge and the rear edge and the welding optimization process parameters of a titanium alloy plate, the fitting track is planned according to an automatic welding system, the compressor blade with a full weld joint shape and no collapse of the front edge and the rear edge can be welded, and the repairing quality and accuracy of the blade are guaranteed.
Drawings
FIG. 1 is a schematic structural view of damaged blades of an aircraft engine compressor according to the present invention;
FIG. 2 is a diagram showing the effect of the titanium alloy after acid washing according to the present invention; (a) the front cleaning effect picture is shown, and the (b) is the side cleaning effect picture;
FIG. 3 is a schematic diagram of the cutting process of a titanium alloy blade of an aircraft engine compressor according to the invention;
FIG. 4 is a schematic diagram of a welding track planning of a titanium alloy blade of an aircraft engine compressor according to the invention;
FIG. 5 is a schematic view of a compressor blade structure after build-up welding in accordance with the present invention;
FIG. 6 is a schematic view of a compressor blade after electrochemical machining.
Detailed Description
The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
The method for repairing the titanium alloy blade of the air compressor of the aircraft engine is characterized by comprising the following steps of: the repairing method comprises the following steps:
step 1, cleaning the blade before welding: for the damaged compressor blade shown in fig. 1, firstly, the blade is preliminarily cleaned by organic solvents such as acetone, and residual sealing rings, sealing gaskets, lubricants and the like on the blade are thoroughly cleaned; the oxide film on the surface of the blade is cleaned by acid washing, and the formula of the acid washing solution is as follows: 10-20% of nitric acid, 50-60% of hydrofluoric acid and the balance of distilled water, wherein the pickling temperature is 30-60 ℃, the pickling time is 1-10 minutes, no oxide film residue exists on the surface of the titanium alloy cleaned by the process, and the pickling corrosion amount is 0.02 mm; the titanium alloy sample after cleaning is shown in fig. 2.
Step 2, processing a part to be welded: as shown in figure 3, after the damaged part is cut by a water jet, the cut surface is polished from coarse to fine until the roughness is better than Ra0.1-0.05.
Step 3, nondestructive testing before welding: the blade is inspected for cracks according to the fluorescent liquid penetrant inspection standard and if a crack is found that is not removed by machining, step 1 is repeated.
And 4, micro-plasma arc welding: clamping by adopting a flexible clamping mechanism, wherein the surface to be welded of the damaged blade is required to be 0.5-3.0 mm higher than the chuck; determining the number of weld passes for surfacing repair according to the missing size of the profile of the blade and the surfacing height of each weld joint; as shown in fig. 4, a visual system is adopted to extract the contour of the surface to be welded of the blade through gray scale change, the welding track is set as the center line of the surface to be welded, the arc starting position is set to be 0.5-3.0 mm in front of the front edge of the surface to be welded of the blade, the arc receiving position is set to be 0.5-3.0 mm behind the rear edge of the surface to be welded of the blade, and the height of the arc starting/receiving position is 2.0-5.0mm above the surface to be welded of the blade; in the welding process, high-purity argon is adopted to construct a triple protective atmosphere, wherein a molten pool protective gas (with the flow rate of 20-40SCFH) outlet is positioned right above a molten pool and blows towards the molten pool vertically downwards, a welding seam front protective gas (100-200 SCFH) outlet is positioned right above a welding seam and blows towards the welding seam vertically downwards, and a welding seam back protective gas (3-10 SCFH) outlet is positioned on a blade clamping tool and blows towards the root of the welding seam laterally; the welding process is as follows:
(1) moving a welding gun to an arc striking position, starting molten pool shielding gas, welding seam front shielding gas and welding seam back shielding gas, staying for 20-50 seconds, and removing air in a welding area to avoid elements such as oxygen, nitrogen and hydrogen in the air from entering a molten pool to deteriorate the performance of a welding joint;
(2) keeping for 1-10 s after arcing at an arcing position, keeping the welding current at a lower power after plasma arc is stabilized, moving a welding gun to be 2.0-5.0mm right above the front edge of the surface to be welded of the blade under the guidance of a manipulator, and carrying out surfacing welding at a lower power and a larger wire feeding amount to enable the front edge of a surfacing area of the blade to be full and leave enough machining allowance;
(3) the welding gun continues surfacing at a welding heat input amount and a wire feeding speed which are suitable for the width of the welding seam;
(4) starting to reduce welding current at a position 2-10mm away from the rear edge of the blade, improving the wire feeding speed, and moving a welding gun to the arc closing position of the blade under the guidance of a manipulator to avoid the collapse of the rear edge;
(5) and closing the plasma arc at the arc withdrawing position, simultaneously drawing back the welding wire to separate from the molten pool, and closing the protective gas after the temperature of the surfacing area is cooled to be lower than 200 ℃ to finish the first welding seam surfacing. If the number of welding passes is more than 1, the welding process can be repeated until the designed number of welding passes is reached, and the compressor blade after surfacing is finished is shown in figure 5.
Step 5, postweld heat treatment: and (3) performing stress relief heat treatment in a vacuum or argon atmosphere environment, wherein the heat treatment temperature is not higher than the phase transition temperature of the titanium alloy.
Step 6, electrolytic machining after welding: removing redundant titanium alloy in a surfacing area through electrolytic machining, wherein a cathode of the electrolytic machining adopts a dispersed water-leaving scheme, NaCl is used as the basis of the electrolyte, and a complexing agent is added; the electrolytic voltage is 20V, and the current density is 55-65A/cm2The machining gap is 0.2-1.8 cm, and the machining speed is 0.15-0.20 mm/s. The compressor blade after electrolytic machining is shown in fig. 6.
Step 7, nondestructive testing after welding: visual detection of appearance, X transmission detection and fluorescence penetration detection are adopted, meanwhile, the relevant sizes of the leaves are detected, the damaged repairing area is determined to be complete and clean, the defects such as undercut and holes do not exist, the front edge and the rear edge of the repairing area are full in appearance and do not collapse, and the appearance color is silvery white or light golden yellow.
Although the embodiments of the present invention and the accompanying drawings are disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the disclosure of the embodiments and the accompanying drawings.