1. A strengthening method for improving the surface quality of an exhaust casing is characterized in that:

(1) fixing parts: the exhaust casing (4) is fixed on a mechanical arm flange plate (5) through a fixing device;

(2) laser shock peening: the method comprises the following steps of applying adhesive tape or aluminum foil on the surface of an area to be strengthened of an exhaust casing (4), applying a layer of stable flowing water film on the surface of the area to be strengthened, wherein the thickness of the water film is 1-3 mm, the width of the water film is 5-15 mm, and performing surface strengthening on the area to be strengthened of the exhaust casing (4) by adopting laser shock strengthening equipment, wherein the process parameters are as follows: the laser power density range is 1GW/cm²～10GW/cm²The effective spot size is phi 1 mm-phi 5mm, the laser pulse width is 10 nm-28 nm, the overlap ratio between spots is 30% -70%, and the laser scanning mode is S-type or II-type;

(3) mechanical shot peening: the matching surface and the screwed hole spraying-forbidden area of the exhaust casing (4) are shielded by adopting an adhesive tape, secondary surface strengthening is carried out on the to-be-strengthened area of the exhaust casing (4) by adopting pneumatic mechanical shot blasting strengthening equipment, and the technological parameters are as follows: the shot is ceramic shot, the shot blasting strength is 0.07A-0.30A, and the shot blasting coverage rate is 100-400%;

(4) cleaning: tearing off the adhesive tape, blowing off the residual shot on the surface of the exhaust casing (4) by adopting compressed air, cleaning all the surfaces of the exhaust casing (4) by adopting alcohol and acetone, and packaging and boxing after drying.

2. An enhanced method of improving the surface quality of an exhaust casing according to claim 1, wherein: the area to be strengthened is a fillet (9) of a support plate (8) of the exhaust casing (4), and a disc body and a support plate surface which are connected with the fillet (9), and the distance range between the surfaces and the fillet (9) is 0-50 mm.

3. An enhanced method of improving the surface quality of an exhaust casing according to claim 1, wherein: firstly, carrying out laser shock strengthening on a fillet (9) of a large surface (901) of a support plate (8) of an exhaust casing (4), and strengthening surface by surface; then carrying out laser shock strengthening on the fillet (9) of the side surface (902) of the support plate (8) of the exhaust casing (4), and strengthening face by face; the range of the boundary allowing the overlapping of the large face 901 and the side face 902 is 1mm to 5 mm.

4. An enhanced method of improving the surface quality of an exhaust casing according to claim 1, wherein: the mechanical shot peening region should cover the entire laser shock peening region and have an area 5% to 25% larger than the area of the laser shock peening region.

5. An enhanced method of improving the surface quality of an exhaust casing according to claim 1, wherein: the surface roughness value after laser shock strengthening is not more than Ra3.2 mu m.

6. An enhancement method for improving the surface quality of an exhaust casing according to any one of claims 1 to 5, wherein: the fixing device consists of a locking end (1), a fixing end (2), a positioning pin (3), a mechanical arm flange plate (5), an inner hexagonal socket head cap screw (6) and a connecting bolt (7); the air inlet end of the exhaust casing (4) is connected with the locking end (1), the exhaust end of the exhaust casing (4) is connected with the fixed end (2), and the locking end (1) and the fixed end (2) are fixedly connected through a connecting bolt (7); the fixed end (2) is connected with a mechanical arm flange plate (5), is positioned by a positioning pin (3) and is fixed by an inner hexagonal cylindrical head screw (6); the locking end (1) can also be connected with a mechanical arm flange plate (5), is positioned by a positioning pin (3) and is fixed by an inner hexagonal socket head cap screw (6).

7. An enhanced method of improving the surface quality of an exhaust casing according to claim 6, wherein: the shape structure of the locking end (1) is composed of three parts, namely a locking flange (101), a casing air inlet end connecting disc (102) and a butt joint disc (103), wherein the flange (101) is fixedly connected with a flange of a robot, the casing connecting disc (102) is fixedly connected with an inner flow air inlet end of a casing, and the butt joint disc (103) is fixedly connected with a fixing disc (203) of the fixing end (2).

8. An enhanced method of improving the surface quality of an exhaust casing according to claim 6, wherein: the fixed end (2) is composed of a fixed flange disc (201), a casing exhaust end connecting disc (202) and a fixed disc (203), the flange disc (201) is fixedly connected with a flange disc (5) of a robot, the casing connecting disc (202) is fixedly connected with an inner flow exhaust end of a casing, and the fixed disc (203) is fixedly connected with a butt joint disc (103) of the locking end (1).

9. An enhanced method of improving the surface quality of an exhaust casing according to claim 4, wherein: the coaxiality of the air inlet end of the clamped exhaust casing (4) and the flange plate (5) of the robot is not more than phi 0.05 mm.

10. An enhanced method of improving the surface quality of an exhaust casing according to claim 4, wherein: the locking end (1) and the fixing end (2) are made of stainless steel or die steel.

Background

The aeroengine exhaust casing is positioned at the tail part of the engine and is mainly used for fixing a turbine part of the engine and outputting residual fuel gas. The exhaust casing is usually cast by high-temperature alloy, bears multiple loads such as high-temperature heat flow impact, cyclic load and the like, and is easy to generate high-temperature fatigue failure at parts such as a fillet, an injection groove and the like of a support plate after service. The main reasons are that: 1) residual tensile stress distribution exists on the surface of the cast exhaust casing, and fatigue cracks are easy to initiate and expand at high stress concentration parts such as fillets and injection grooves of the support plate under the action of alternating load; 2) the surface roughness value of the cast exhaust casing is larger (more than or equal to Ra6.0 mu m), high local surface stress concentration is generated, and fatigue cracks are easily induced. At present, the main method for improving the exhaust casing is to reduce the residual tensile stress of the surface by stress relief annealing and then reduce the roughness value of the surface by vibration finishing. The method can reduce the amplitude of the residual tensile stress to a certain extent and properly reduce the surface roughness value (Ra3.2-Ra6.0 mu m), but cannot generate high-amplitude residual compressive stress distribution and deep tissue hardening layers on the surface, and has very limited improvement on the high-temperature fatigue performance, so that a novel surface treatment technology is urgently needed to obviously improve the surface quality of the exhaust casing and improve the high-temperature fatigue performance.

Disclosure of Invention

The purpose of the invention is: a strengthening method for improving the surface quality of an exhaust casing is provided, which obtains high-amplitude surface residual compressive stress distribution and a deep hardened layer in a region to be strengthened of the exhaust casing, and obviously reduces the surface roughness value of the region to be strengthened, thereby providing a technical approach for improving the surface quality of the exhaust casing and improving the high-temperature fatigue performance.

The technical scheme of the invention is as follows:

a strengthening method for improving the surface quality of an exhaust casing is characterized in that:

(1) fixing parts: fixing an exhaust casing on a mechanical arm flange plate through a fixing device;

(2) laser shock peening: the method comprises the following steps of applying adhesive tape or aluminum foil on the surface of an area to be strengthened of the exhaust casing, applying a layer of stable flowing water film on the surface of the area to be strengthened, wherein the thickness of the water film is 1-3 mm, the width of the water film is 5-15 mm, and performing surface strengthening on the area to be strengthened of the exhaust casing by adopting laser shock strengthening equipment, wherein the process parameters are as follows: the laser power density range is 1GW/cm 2-10 GW/cm2, the effective spot size is phi 1 mm-phi 5mm, the laser pulse width is 10 nm-28 nm, the lap joint rate between spots is 30% -70%, and the laser scanning mode is S type or II type.

(3) Mechanical shot peening: the matching surface and the threaded hole spraying-forbidden area of the exhaust casing are shielded by adopting an adhesive tape, secondary surface strengthening is carried out on the area to be strengthened of the exhaust casing by adopting pneumatic mechanical shot blasting strengthening equipment, and the technological parameters are as follows: the shot is ceramic shot, the shot blasting strength is 0.07A-0.30A, and the shot blasting coverage rate is 100-400%;

(4) cleaning: tearing off the adhesive tape, blowing off the residual bullets on the surface of the exhaust case by adopting compressed air, cleaning all the surfaces of the exhaust case by adopting alcohol and acetone, drying, packaging and boxing.

The area to be strengthened is the fillet of the support plate of the exhaust casing, and the disc body and the support plate surface bordering on the fillet, and the distance range between the surfaces and the fillet is 0-50 mm.

Firstly, carrying out laser shock strengthening on the round corners of the large surface of the support plate of the exhaust casing, and strengthening the round corners one by one; then carrying out laser shock strengthening on the round corners of the side surfaces of the support plates of the exhaust casing, and strengthening the round corners one by one; the margin for allowing overlap on the large face and the side face ranges from 1mm to 5 mm.

The mechanical shot peening region should cover the entire laser shock peening region and have an area 5% to 25% larger than the area of the laser shock peening region.

The surface roughness value after laser shock strengthening is not more than Ra3.2 mu m.

The fixing device consists of a locking end, a fixing end, a positioning pin, a mechanical arm flange plate, an inner hexagonal socket head cap screw and a connecting bolt; the air inlet end of the exhaust casing is connected with the locking end, the exhaust end of the exhaust casing is connected with the fixed end, and the locking end and the fixed end are fixedly connected through a connecting bolt; the fixed end is connected with the mechanical arm flange plate, is positioned by a positioning pin and is fixed by an inner hexagonal socket head cap screw; the locking end can also be connected with the mechanical arm flange plate, positioned by a positioning pin and fixed by an inner hexagonal socket head cap screw.

The shape structure of the locking end is composed of a locking flange, a connection disc of the air inlet end of the casing and a butt joint disc, the flange is fixedly connected with the flange of the robot, the connection disc of the casing is fixedly connected with the inner flow air inlet end of the casing, and the butt joint disc is fixedly connected with a fixed disc of the fixed end.

The fixed end consists of three parts, namely a fixed flange plate, a casing exhaust end connecting plate and a fixed disk, the flange plate is connected and fixed with the flange plate of the robot, the casing connecting plate is connected and fixed with the inner flow exhaust end of the casing, and the fixed disk is connected and fixed with the butt joint plate of the locking end.

The coaxiality of the air inlet end of the clamped exhaust casing and a flange plate of the robot is not more than phi 0.05 mm.

The locking end and the fixing end are made of stainless steel or die steel.

The invention has the advantages that:

firstly, after the fillet of the support plate of the exhaust casing is treated by two surface strengthening methods of laser impact and mechanical shot blasting, the residual compressive stress value on the surface can reach-800 MPa to-1000 MPa, the depth of a hardened layer is 0.2 to 0.3mm, the surface roughness value is reduced to the range of Ra2.0 to Ra3.2 mu m from more than or equal to Ra6.0 mu m, and the good surface quality is favorable for improving the high-temperature fatigue life of the exhaust casing.

Secondly, after the treatment by the method, the surface quality presents good high-temperature thermal stability, after the treatment by the method at 647 ℃ and in the atmospheric atmosphere, the residual stress distribution on the surface still remains and is in the range of-200 MPa to-500 MPa, the depth of a hardened layer still remains at 0.2-0.3 mm, the surface roughness value is not changed obviously, and the good high-temperature thermal stability is beneficial to prolonging the service life of the exhaust casing.

Drawings

FIG. 1 is a schematic view of the apparatus of the present invention

FIG. 2 is a schematic view of the area of the exhaust casing to be reinforced

Detailed Description

The object to be processed is an as-cast exhaust casing having a surface roughness of Ra6.0 to 7.2 μm and a residual tensile stress state (+50 to +200MPa) on the surface. The fatigue critical area of the exhaust casing is easy to generate fatigue failure, the surface quality of the fatigue critical area is improved through a laser shock peening and shot peening process, the fatigue critical area becomes an area to be strengthened, namely a fillet 9 of a support plate 8 of the exhaust casing 4, a disc body and the surface of the support plate, wherein the disc body and the surface of the support plate are connected with the fillet 9, and the distance range between the surface and the fillet 9 is 0-50 mm.

In order to improve the surface quality of a fatigue critical area of an exhaust casing, the invention designs a fixing device of the exhaust casing, which consists of a locking end 1, a fixing end 2, a positioning pin 3, a mechanical arm flange 5, an inner hexagonal socket head cap screw 6 and a connecting bolt 7; the air inlet end of the exhaust casing 4 is connected with the locking end 1, the exhaust end of the exhaust casing 4 is connected with the fixed end 2, and the locking end 1 and the fixed end 2 are fixedly connected through a connecting bolt 7; the fixed end 2 is connected with a manipulator flange 5, is positioned by a positioning pin 3 and is fixed by an inner hexagonal socket head cap screw 6; the locking end 1 can also be connected with a manipulator flange 5, positioned by a positioning pin 3 and fixed by an inner hexagonal socket head cap screw 6.

The shape structure of the locking end 1 is composed of three parts, namely a locking flange plate 101, a casing air inlet end connecting plate 102 and a butt joint plate 103, wherein the flange plate 101 is fixedly connected with a flange plate of a robot, the casing connecting plate 102 is fixedly connected with an inner flow air inlet end of a casing, and the butt joint plate 103 is fixedly connected with a fixed plate 203 of a fixed end 2. The locking end 1 is made of stainless steel or die steel.

The shape structure of the fixed end 2 is composed of three parts, namely a fixed flange plate 201, a casing exhaust end connecting plate 202 and a fixed plate 203, wherein the flange plate 201 is fixedly connected with a flange plate 5 of the robot, the casing connecting plate 202 is fixedly connected with the inner flow exhaust end of the casing, and the fixed plate 203 is fixedly connected with a butt joint plate 103 of the locking end 1. The fixed end 2 is made of stainless steel or die steel.

On the basis, the invention provides a strengthening method for improving the surface quality of an exhaust casing, which comprises the following specific steps:

(1) fixing parts: the exhaust casing 4 is fixed on a manipulator flange 5 through a fixing device; the coaxiality of the air inlet end of the clamped exhaust casing 4 and the flange 5 of the robot is not more than phi 0.05 mm.

(2) Laser shock peening: the method comprises the following steps of applying adhesive tape or aluminum foil on the surface of an area to be strengthened of an exhaust casing 4, applying a layer of stable flowing water film on the surface of the area to be strengthened, wherein the thickness of the water film is about 1-3 mm, the width of the water film is 5-15 mm, and performing surface strengthening on the area to be strengthened of the exhaust casing 4 by adopting laser shock strengthening equipment, wherein the process parameters are as follows: the laser power density range is 1GW/cm²～10GW/cm²The effective spot size is phi 1 mm-phi 5mm, the laser pulse width is 10 nm-28 nm, the overlap ratio between spots is 30% -70%, and the laser scanning mode is S-type or II-type. Firstly, carrying out laser shock strengthening on the round corners 9 of the large surfaces 901 of the support plates 8 of the exhaust casing 4, and strengthening surface by surface; then carrying out laser shock strengthening on the round corners 9 of the side surfaces 902 of the support plates 8 of the exhaust casing 4, and strengthening one by one; the boundary allowing the overlap on the large face 901 and the side face 902 ranges from 1mm to 5 mm.

(3) Mechanical shot peening: the matching surface and the screwed hole spraying-forbidden area of the exhaust casing 4 are shielded by adopting an adhesive tape, secondary surface strengthening is carried out on the to-be-strengthened area of the exhaust casing 4 by adopting pneumatic mechanical shot blasting strengthening equipment, and the technological parameters are as follows: the shot is ceramic shot, the shot blasting strength is 0.07A-0.30A, and the shot blasting coverage rate is 100-400%; the mechanical shot peening region should cover the entire laser shock peening region and have an area 5% to 25% larger than the area of the laser shock peening region.

(4) Cleaning: tearing off the adhesive tape, blowing off the residual shot on the surface of the exhaust casing 4 by adopting compressed air, cleaning all the surfaces of the exhaust casing 4 by adopting alcohol and acetone, drying, packaging and boxing.

Compared with the non-strengthened state, the surface roughness is reduced by 20 to 30 percent after laser shock strengthening; after mechanical shot blasting, the surface roughness is reduced by 10-20 percent, and finally, the surface roughness value is not more than Ra3.2 mu m.

The working principle of the invention is as follows:

this patent treats the intensive district earlier and carries out laser shock peening, can make exhaust casing metal surface take place plastic deformation, forms high-amplitude residual compressive stress distribution (-800 MPa-1000 MPa) and deep tissue hardening layer (0.2 ~ 0.3mm), reduces the surface roughness value (reduces 20% ~ 30%) simultaneously, is favorable to improving the resistance that fatigue crack initiation and early crack propagation.

And then, carrying out mechanical shot blasting reinforcement on the region to be reinforced to form surface residual stress distribution with high amplitude and good two-dimensional uniformity on the metal surface of the exhaust casing, and obviously reducing the original higher surface roughness value (reduced by 10-20%) of the cast alloy by repeatedly impacting the surface of the material by a large number of shots to reach Ra2.0-Ra3.2 mu m, thereby reducing the local stress concentration of the surface of the material.

When the two processes are superposed, the mechanical shot peening strengthening region covers the whole laser shock strengthening region, the area of the mechanical shot peening strengthening region is 5% -25% larger than that of the laser shock strengthening region, a gradual transition region of residual compressive stress can be formed between the laser shock strengthening region and the unreinforced region, and stress concentration is favorably reduced.

Example 1

The object to be processed is an as-cast exhaust casing having a surface roughness of Ra6.0 to 7.2 μm and a residual tensile stress state (+50 to +200MPa) on the surface. The fatigue critical area of the exhaust casing is easy to generate fatigue failure, the surface quality of the fatigue critical area is improved through a laser shock peening and shot peening process, the fatigue critical area becomes an area to be strengthened, namely a fillet 9 of a support plate 8 of the exhaust casing 4, a disc body and a support plate surface which are connected with the fillet 9, and the distance range between the surface and the fillet 9 is 50 mm.

In order to improve the surface quality of a fatigue critical area of an exhaust casing, the invention designs a fixing device of the exhaust casing, which consists of a locking end 1, a fixing end 2, a positioning pin 3, a mechanical arm flange 5, an inner hexagonal socket head cap screw 6 and a connecting bolt 7; the air inlet end of the exhaust casing 4 is connected with the locking end 1, the exhaust end of the exhaust casing 4 is connected with the fixed end 2, and the locking end 1 and the fixed end 2 are fixedly connected through a connecting bolt 7; the fixed end 2 is connected with a manipulator flange 5, is positioned by a positioning pin 3 and is fixed by an inner hexagonal socket head cap screw 6; the locking end 1 can also be connected with a manipulator flange 5, positioned by a positioning pin 3 and fixed by an inner hexagonal socket head cap screw 6.

The shape structure of the locking end 1 is composed of three parts, namely a locking flange plate 101, a casing air inlet end connecting plate 102 and a butt joint plate 103, wherein the flange plate 101 is fixedly connected with a flange plate of a robot, the casing connecting plate 102 is fixedly connected with an inner flow air inlet end of a casing, and the butt joint plate 103 is fixedly connected with a fixed plate 203 of a fixed end 2. The locking end 1 is made of stainless steel.

The shape structure of the fixed end 2 is composed of three parts, namely a fixed flange plate 201, a casing exhaust end connecting plate 202 and a fixed plate 203, wherein the flange plate 201 is fixedly connected with a flange plate 5 of the robot, the casing connecting plate 202 is fixedly connected with the inner flow exhaust end of the casing, and the fixed plate 203 is fixedly connected with a butt joint plate 103 of the locking end 1. The fixed end 2 is made of die steel.

On the basis, the invention provides a strengthening method for improving the surface quality of an exhaust casing, which comprises the following specific steps:

(1) fixing parts: the exhaust casing 4 is fixed on a manipulator flange 5 through a fixing device; the coaxiality of the air inlet end of the clamped exhaust casing 4 and the flange 5 of the robot is 0.05 mm.

(2) Laser shock peening: the method comprises the following steps of applying an adhesive tape on the surface of an area to be strengthened of the exhaust casing 4, applying a layer of stable flowing water film on the surface of the area to be strengthened, wherein the thickness of the water film is about 2mm, the width of the water film is 15mm, and performing surface strengthening on the area to be strengthened of the exhaust casing 4 by adopting laser shock strengthening equipment, wherein the process parameters are as follows: the laser power density range is 10GW/cm²The effective spot size is phi 3mm, the laser pulse width is 28nm, the overlap ratio between spots is 70%, and the laser scanning mode is S-shaped. Firstly, carrying out laser shock strengthening on the round corners 9 of the large surfaces 901 of the support plates 8 of the exhaust casing 4, and strengthening surface by surface; then carrying out laser shock strengthening on the round corners 9 of the side surfaces 902 of the support plates 8 of the exhaust casing 4, and strengthening one by one; the boundary range allowing overlap on the large face 901 and the side face 902 is 5 mm.

(3) Mechanical shot peening: the matching surface and the screwed hole spraying-forbidden area of the exhaust casing 4 are shielded by adopting an adhesive tape, secondary surface strengthening is carried out on the to-be-strengthened area of the exhaust casing 4 by adopting pneumatic mechanical shot blasting strengthening equipment, and the technological parameters are as follows: the shot is ceramic shot, the shot blasting strength is 0.07A, and the shot blasting coverage rate is 100-200%; the mechanical shot peening region should cover the entire laser shock peening region and have an area 25% larger than the area of the laser shock peening region.

(4) Cleaning: tearing off the adhesive tape, blowing off the residual shot on the surface of the exhaust casing 4 by adopting compressed air, cleaning all the surfaces of the exhaust casing 4 by adopting alcohol and acetone, drying, packaging and boxing.

Compared with the non-strengthened state, the surface roughness is reduced by 30 percent after laser shock strengthening; after mechanical shot blasting, the surface roughness is reduced by 20 percent, and finally, the surface roughness value reaches Ra2.0-Ra3.2 mu m.

Example 2

The thickness of the water film is about 1mm, the width is 5mm, the laser shock peening equipment is adopted to carry out surface strengthening on the area to be strengthened of the exhaust casing 4, and the technological parameters are as follows: the laser power density range is 1GW/cm²The effective spot size is phi 1mm, the laser pulse width is 10nm, the overlap ratio between spots is 70%, and the laser scanning mode is II type.The margin of overlap allowed on the large face 901 and the side face 902 is 1 mm.

The shot blasting strength is 0.30A, and the shot blasting coverage rate is 200-400%; the mechanical shot peening region should cover the entire laser shock peening region and have an area 5% larger than the area of the laser shock peening region.

Compared with the non-strengthened state, the surface roughness is reduced by 20% after laser shock strengthening; after mechanical shot blasting, the surface roughness is reduced by 20 percent, and finally, the surface roughness value Ra2.6-Ra3.2 mu m.