EP0074918B1 - Procédé de grenaillage et polissage simultanés - Google Patents

Procédé de grenaillage et polissage simultanés Download PDF

Info

Publication number
EP0074918B1
EP0074918B1 EP82630084A EP82630084A EP0074918B1 EP 0074918 B1 EP0074918 B1 EP 0074918B1 EP 82630084 A EP82630084 A EP 82630084A EP 82630084 A EP82630084 A EP 82630084A EP 0074918 B1 EP0074918 B1 EP 0074918B1
Authority
EP
European Patent Office
Prior art keywords
shot
workpiece
peening
range
surface finish
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP82630084A
Other languages
German (de)
English (en)
Other versions
EP0074918A3 (en
EP0074918A2 (fr
Inventor
James Wesley Neal
Joseph Frederick Loersch
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Raytheon Technologies Corp
Original Assignee
United Technologies Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US06/300,727 external-priority patent/US4514469A/en
Priority claimed from US06/300,718 external-priority patent/US4426867A/en
Priority claimed from US06/300,725 external-priority patent/US4454740A/en
Application filed by United Technologies Corp filed Critical United Technologies Corp
Publication of EP0074918A2 publication Critical patent/EP0074918A2/fr
Publication of EP0074918A3 publication Critical patent/EP0074918A3/en
Application granted granted Critical
Publication of EP0074918B1 publication Critical patent/EP0074918B1/fr
Expired legal-status Critical Current

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C24/00—Coating starting from inorganic powder
    • C23C24/02—Coating starting from inorganic powder by application of pressure only
    • C23C24/04—Impact or kinetic deposition of particles
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
    • C21D7/04—Modifying the physical properties of iron or steel by deformation by cold working of the surface
    • C21D7/06—Modifying the physical properties of iron or steel by deformation by cold working of the surface by shot-peening or the like
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working

Definitions

  • the present invention concerns a method of surface treating a workpiece, to provide residual compressive stresses corresponding to a peening intensity of at least 0.1 mm N and a surface finish smoother than 40 AA by impacting the workpiece with spherical shot particles having a hardness greater than the workpiece.
  • Shot peening is a manufacturing process wherein the surface of a workpiece is impacted by particles or shot.
  • An important use of peening is to generate a residual compressive stress in surface of a metal workpiece, to improve fatigue resistance.
  • localized areas of tensile stress, phase transformations, machine and grinding marks, pits, scratches, and the like, can be blended and effectively eliminated from acting as stress concentration points.
  • Shot peening at low intensities, most often with glass beads, is used in the aircraft gas turbine engine field to enhance the performance of disks, vanes, and blades which are subject to high fatigue stresses. Characteristically, shot peening leaves a textured surface owing to the slightly rounded depressions each particle impact produces.
  • shot size is usually chosen according to the size of the workpiece and finish desired. There are many different choices, as indicated by the specification SAE J444a (Society of Automotive Engineers).
  • the nominal size of shot varies from 4.75 to 0.075 mm, and typically is cast steel or iron material. Glass beads in the range of 1.4 to 0.038 mm nominal diameter are also commonly used.
  • Commercial shot is characterized by a relatively wide particle distribution about the mean or nominal size. In addition, the shot tends to fragment during use, leading to the presence of smaller jagged fragments. As a result, shot peening gives a textured surface finish and the surface finish can vary over time with a given shot mass.
  • US-A-937 180 discloses a method of obtaining a mottled effect on otherwise smooth sheets. Hardened steel balls are dropped from a series of funnels onto an inclined sheet workpiece placed below. US-A-3 705 511 describes a low penetration ball forming process, for contouring aluminum sheet which is stretched across a convex die. Steel balls in the range of 3-6 mm diameter fall by gravity from the edge of an inclined surface, impacting the exposed convex surface of the sheet at about 5 m/sec.
  • the workpiece is translated under the shot stream for a time sufficient to permanently deform the sheet (owing to the residual stresses) but insufficient to deform the sheet greater than the die shape provides.
  • the contouring process is followed by a conventional shot peening using smaller S230 (-0.7 mm) shot, to obtain the requisite uniform residual stress for fatigue resistance.
  • the method of the present invention is characterized in that said impacting is carried out with shot particles being infrangible, having a surface finish better than 30 AA and diameters lying in the range of 1-2.5 mm which are substantially uniform to within at least ⁇ 0.5%.
  • An object of the invention is to produce parts having both a uniform residual surface stress state and a smooth surface finish.
  • the method of the invention is based on the discovery of critical interdependencies between shot size, energy, peening intensity, and surface finish.
  • a workpiece is simultaneously provided with compressive stresses corresponding to a peening intensity of 0.1 mm N or greater, and a surface finish smoother than 40 AA by impacting it with spherical shot having substantially uniform diameter in the range 1-2.5 mm, preferably 1.5-2 mm, traveling at a substantially uniform velocity.
  • the shot must be infrangible, so it maintains its sphericity in use, and have a surface finish better than 30 AA.
  • substantially uniform diameter is meant that the shot body will be comprised of particles having diameters within about ⁇ 0.05 mm, or uniform within ⁇ 5%. This will provide unit masses uniform within about ⁇ 16%.
  • the shot is impacted on the workpiece at a velocity less than 15 meter/sec, preferably in the range 1.4-12 m/s, more preferably in the range 2.5-7.8 m/s.
  • the impact velocity will vary according to the desired peening intensity and the diameter of the shot used, with higher velocities being associated with higher intensity and smaller diameter.
  • the impact velocity will be uniform within about ⁇ 4% when the preferred method of acceleration, by force of gravity, is used.
  • Resultant unit impact energies will be uniform within about ⁇ 25%, in the range of 0.2x 10- 4 to 12x10- 4 J.
  • the final surface finish depends on the initial finish. If a titanium workpiece surface has an initial finish of less than about 40 AA, the process is capable of producing final finishes of 15 AA or better. When the workpiece is provided with a smoother initial finish, final finishes down to 6 AA are attainable.
  • the workpiece finish is dependent on the peening intensity and diameter of shot. For any given shot size, higher peening intensities are associated with poorer finishes. However, at any given intensity a better finish is produced by a larger shot size. As an example, to obtain better than 15 AA surface finish, the intensity of shot peening must be less than about 0.30 mm N. Using 1.8 mm shot enables up to about 0.50 mm N. As a corollary, at any given peening intensity the finish will be better for the larger shot.
  • shot significantly smaller than 1 mm will not be capable of producing a requisite smooth surface of 15 AA, whereas shot greater than 2 mm gives a good finish, but without advantage over 2 mm shot.
  • Shot up to 2.5 mm is useful, nonetheless, when high peening intensities are required. But associated with larger shot and especially that over 2.5 mm are long peening (saturation) times and low impact velocities which introduce practical problems in controlling uniformity and obtaining good results on inside radius contours.
  • the invention also improves the properties of overlay coatings, such as physical vapor deposition (PVD) and plasma are sprayed coatings.
  • PVD physical vapor deposition
  • plasma coatings For example, 0.13 mm thick MCrAIY PVD and plasma coatings are peened with 1-2.5 mm shot to an intensity of 0.3-0.6 mm N and subsequently heat treated. Not only are leaders and voids in the coatings healed to a degree greater than possible with the prior art air propelled glass bead peening, but the coatings are substantially smoothed.
  • PVD coatings of 60 AA finish are improved to 25-35 AA while plasma coatings with 300 AA finish are improved to finishes of less than 100 AA.
  • the workpiece When the invention is applied to thin edged workpieces such as gas turbine airfoils, the workpiece is manipulated with respect to the collimated shot stream in a manner which avoids damage to the thin edges but at the same time produces the desired residual compressive stress in the edge.
  • the manipulating involves careful rotation of the workpiece about an axis parallel to the edge so that only a portion of the edge is presented to the collimated shot stream; direct impacts on the centerline of the edge are avoided.
  • first one side and then the other side of the airfoil is presented to the shot stream. When each side is presented the airfoil is given an oscillatory rotation about its longitudinal axis to thereby finish both of the opposing edges.
  • the invention herein is described in terms of the finishing of a titanium alloy (Ti-6A1-4V by weight) blade designed for use in the compressor section of a gas turbine engine.
  • the invention is also described in terms of attaining the following objectives: a surface finish of better than 15 AA and a residual compressive stress intensity of 0.25­0.30 N, (in millimeters according to the Almen test). Both parameters are described in more detail below.
  • the invention will be useful for finishing other workpieces and metals to other criteria; such as where the surface finish may range up to 40 AA, and the intensity may range between 0.10-1.0 N.
  • the present invention employs very uniform sized spherical shot, such as utilized in the construction of ball bearings.
  • the hardness of the shot should be greater than the hardness of the metal being peened, to insure that the shot is not deformed during use.
  • a preferred material for peening Ti-6A1-4V (having a hardness of about Rc 40) is a carbon tool steel, such as AISI C1013, which has been heat treated to a hardness in the range of Rc 60. It is preferred that the shot be of a relatively high density material such as steel.
  • the shot material must be infrangible to avoid generation of subsized particles during peening; the importance of this is indicated below.
  • the shot of the present invention is seen to be uniform within a tolerance of a plus or minus 0.05 mm.
  • SAE and MIL-SPEC grades of shot it is expected that there is a normal distribution which includes a certain number of fine shot particles. This is evidenced by the lack of a screen specification for the 99-100% cumulative percentage.
  • the grades of shot used in the invention typified by the NL grades, have 100 percent of the shot entirely within a specified narrow range.
  • the shot be spherical.
  • any characteristic shot particle should have a radius which does not vary by more than about 2 percent.
  • the sphericity requirements will be understood within the context of the size uniformity requirements, elaborated upon further herein. Irregular shaped shot can provide impacts which are of lower or greater intensity than their spherical equivalent and may not provide the good results of the invention.
  • the invention provides a smooth surface finish on the workpiece being peened, better than 40 AA, and as low as 6 AA.
  • the shot particles Preferably, the shot should have a finish of 6 AA or better. But, when less fine finish is desired, somewhat poorer shot surface finishes may be usable, up to about 30 AA.
  • the foregoing surface finish requirement in combination with the sphericity requirement precludes the use of shot containing fragments.
  • Shot particles must have substantially uniform energy when they impact the workpiece surface.
  • the preferred way to achieve this is to discharge the uniform sized shot from a discharge gate (perforated plate) positioned above the workpiece, with a very low uniform velocity. The shot is then allowed to fall by the force of gravity. This will impart to all shot, regardless of size, a uniform acceleration and impact velocity. The velocity at the time of impact will depend on the height of the gate above the workpiece.
  • h the height
  • g the gravitational constant
  • the intensity of shot peening, I was measured using the aforementioned Almen steel strip.
  • the surface finish of the titaniums was measured using a standard surface finish measuring system, such as a Bendix Model QEH Digital Profilometer and Amplimeter Peak Counter (Bendix Automation & Measurement Division, Dayton, Ohio).
  • Saturation time is a shot peening parameter which is a measure of the time at which peening of the surface is deemed to be complete; it is determined with the use of an Almen strip. Saturation time is defined as that time, which when doubled, causes less than a 10% increase in measured intensity. Low saturation times are desired for economic production.
  • Table 2 shows various parameters measured for three shot sizes.
  • peening intensity I(N); drop height, h; saturation time, T; total energy, E t (the product of one-half the total mass flow per unit area, over time T, and the square of the shot impact velocity); the efficiency, Eff, which is the ratio of the impact energy, less the rebound energy, to the impact energy of a shot particle, and it is a measure of the energy transferred to the workpiece by the shot; the energy transferred, E tr , which is the product of E t and Eff; and the surface finish, SF.
  • Figure 4 shows the efficiency data from the table, plotted as a function of drop height for different shot diameters.
  • Figure 5 illustrates the relationship between drop height and the shot size at I of 0.25 N.
  • the drop height decreases geometrically as shot diameter increases. From Figure 5 it may be seen that when the shot diameter reaches 2.5-3 mm the permissabIe h becomes small at about 0.25-0.40 m. Such small drop heights are to be avoided, since associated with them are very low impact velocities, less than about 3 m/sec; these make fluctuations in initial velocity more critical.
  • a contoured workpiece such as an airfoil, and particularly one which is rotated or inclined with respect to the shot streamline, may vary in height in space by as much as 50 mm.
  • Figure 6 illustrates the surface finish that is obtained at saturation time T, when titanium alloy workpieces are subjected to different peening intensities with different sized shot.
  • T saturation time
  • Figure 6 also shows how 1 and 1.8 mm shot are effective in reducing the surface finish of a previously rough surface.
  • a GB20 finished panel at 42 AA is provided with a surface of about 15 AA using 1.8 mm shot at 0.25 N.
  • Figure 7 further illustrates the smoothing effect.
  • curves A and B there is initially a roughening of initially smooth specimens, followed by smoothing at T, and still further smoothing if peening is continued.
  • curve C illustrates.
  • Curve D illustrates the roughening which the prior art glass bead peening provides, when saturation time is reached.
  • Curve D portrays the behavior of regular GB20 glass beads. Since within the typical GB20 mass is a certain quantity of broken beads, continued peening time will produce no change in finish. However, if specially selected (virgin, unused) glass beads are used, there can be an improvement of surface finish to the range of 30 AA, if peening is continued beyond saturation time.
  • Figure 8 correlates the foregoing data, showing the important relation of finish with peening intensity. It is seen that as I decreases, the surface finish improves. It is seen that the S110 steel shot and the GB20 glass will not provide the desired results. Only larger shot will produce a very smooth finish while simultaneously providing significant I.
  • the dashed box line on the Figure indicates the desired finish and peening intensities for titanium airfoils. Shot in the range 1-2.5 mm dia. is usable. But, it is seen that for a finish less than 15 AA, the 1 mm shot can only be used up to an I of about 0.30 N. Although data was not obtained it appears evident that shot substantially less than 1 mm, below 0.8 mm, will not be useful.
  • Figure 9 correlates the foregoing data with the input energy, E, which as pointed out was proportionate to drop height, h.
  • the Figure 9 curve is used by first entering at the desired intensity, 0.30 N. Moving to the right, the 1 mm curve is first intersected. Traveling from the intersection vertically downward, the energy per unit shot particle needed to obtain the desired I is indicated as 10- 4 J. (From this the height can be easily calculated). Traveling vertically upward, another curve for 1 mm shot is intersected, and an ordinate location associated therewith indicates a surface finish of about 15 AA will result from the E and shot diameter. Treating the graph similarly for the same 0.30 N, but with 1.8 mm shot diameter shows that higher unit shot energy level of 1.8 ⁇ 10* °J is required but that a better surface finish of 8 AA will be obtained.
  • Figure 10 shows the relationship between shot size and surface finish, utilizing the same data as in Figures 8 and 9. It is seen that when a shot size of greater than about 2 mm is reached there is unexpectedly not a significant further increase in surface finish.
  • Figure 11 is a summary of the prior data and graphically indicates the preferred shot size. It is seen that between 2-2.5 mm diameter, surface finish does not improve, while saturation time goes up substantially. The time disadvantage is more pronounced for the lower I values and has associated with it low drop height. Thus, for I less than 0.40 N, size should be less than 2 mm; for I above 0.40 N, shot size up to 2.5 mm may be used.
  • the shot size should be no less than 1 mm, and preferably greater than 1.5 mm.
  • peening intensities of greater than 0.25 N Most of our concern herein has been with peening intensities of greater than 0.25 N, however, lesser intensities will be on occasion found useful, down to about 0.10 N. They may be provided in the practice of the invention as reference to the figures and limited extrapolation will show. To achieve low intensities, shot diameters from the smaller end of the range will be selected, since required velocities and drop heights become undesirably small for shot in the larger diameter end of the range.
  • the 1-2.5 mm steel shot particles used in our experiments had a diameter tolerance of ⁇ 0.05 mm and a specific gravity of about 7.8. Thus, the diameter was uniform within ⁇ 2.5%.
  • the nominal particle mass ranged between 4-64 x 10- 3 gm; and the mass at a given diameter varied between ⁇ 6-15%, the smaller percentage being associated with the larger shot size.
  • the range of velocity which is usable in the invention is dependent both on the size of the shot (necessary to achieve the energy which produces the desired peening intensity) and practical limits relating to how the shot is accelerated. While we conceive of other means of accelerating shot, only gravity acceleration appears presently to have both simplicity and consistency in providing uniform velocity. Therefore our practical limits are related to the drop heights which are feasible.
  • the drop height should be more than 0.1 m, very preferably greater than 0.3 m, and most preferably in the range 0.6-3 m. When the drop height becomes too low, variations in the placement or controlled movement of the airfoil may significantly affect impact velocity, and thereby the precision of peening required to achieve the objects of the invention.
  • Figure 9 shows the unit shot energy will range from approximately 0.2 ⁇ 10 -4 J to 12x10- 4 J.
  • the unit energy range will be about 0.6x10- 4 to 3x10- 4 J.
  • the mass and velocity must be substantially uniform, within the context of the foregoing tolerances.
  • the mass and velocity tolerances are cumulative in their effect on energy and peening intensity.
  • the permissible tolerance for the energy level within a shot stream depends on the relationship between the desired intensity and finish which has been presented herein, and the requirements of the particular application. Generally, in most applications it is preferred that the energy level be held within about 15 percent for best results and dependable saturation times; with the above presented mass tolerances of ⁇ 6-15% and velocity tolerances of ⁇ 4% (meaning v 2 is ⁇ 16%), a statistical summation indicates energy tolerance is about ⁇ 25%, and this has provided good results.
  • the practice of our invention calls for substantially uniform shot velocities. Uniform velocities may be attained using gravity acceleration. However, any mode of propelling the shot may be used, so long as the criteria of the invention are met. Also, the best mode involves peening in dry air. In special circumstances, the invention may be carried out as well in other environments, such as in liquids or vapors.
  • the invention provides for the use of substantially uniform size shot, it would at first appear that the use of two or more different sizes of shot would not conform with the invention. It is true that the preponderance of the shot must be substantially uniform at the selected size to effectively practice the invention. And inclusion of any significant quantity of shot which is substantially larger than-outside the tolerance of-the selected size will not be in accord. However, the presence of some smaller shot is contemplated as lying within the scope of the invention when such inclusion may be desirable for secondary purposes or is without specific purpose. The reasoning behind this is as follows.
  • the time to saturation is the measure of time upon which the desired residual stress accumulates. This in turn is a direct function of the number of impacts and energy of each impact which the surface receives. Therefore, decreasing the mass flow rate will increase the saturation time in inverse proportion to the change. From the data presented, it will be understood that using gravity accelerated shot, all the shot in a mixed size mass will have the same velocity. The energy will be less for the smaller shot particles and the intensity produced therefrom will be less. Accordingly, it can be seen that if the shot size was mixed, for example if 1.8 and 1 mm shot were mixed together, the time to saturation will be longer than the time for either of the independent shot sizes. Saturation time and intensity will be controlled only by the larger shot size, the mass flow of which would be effectively reduced.
  • the presence of smaller shot will merely serve to extend the saturation time. Where the small shot hits, the I will be lower than that desired, which will be that provided by the larger size shot. In a mixed size shot mass, at best the presence of small shot will be benign. At worst, it will be impelled with unwanted excess energy, as when a large shot drives a small shot against the workpiece, and locally causes a poor surface finish and excess intensity.
  • shot material than the steel of our best embodiment may be used.
  • the shot must of a material harder than the workpiece, and elastic in its impacts with the workpiece and apparatus. It must be substantially infrangible, that is, significant amounts cannot fragment during impact with the workpiece or pieces of the apparatus.
  • the good results we obtained are based on the relationships between energy and diameter. Thus it would appear that, for example, a low density material impelled at a given velocity may produce the same results as a higher density material with the same energy and a lower velocity. While this is true qualitatively, there is probably a velocity effect which we cannot presently fully delineate, and low and high density particles of equal energy may not produce comparable results. Evidently, absolute velocity level is influential.
  • the invention is also useful in the finishing of various kinds of coatings and surface depositions, as illustrated by an MCrAIY coating on a nickel super-alloy gas turbine blade.
  • the coating is deposited by physical vapor deposition (PVD) or plasma spraying.
  • PVD physical vapor deposition
  • MCrAIY coatings are described in U.S. Patents 3,542,530, 3,676,085, 3,918,139 and 3,928,026.
  • PVD coatings When PVD coatings are deposited, they frequently may have defects which are generally characterized as leaders. These are voids which extend transverse to the surface of the substrate, along the direction of the multiplicity of columnar grains which characterizes the coating.
  • a typical coating will be about 0.13 mm thick and it will have nominally the same surface finish as the substrate.
  • the coating is preferably peened using 1.8 mm diameter hardened spherical steel shot using substantially the same practices as above.
  • the shot velocity will lie in the range of 4.7-6.3 meters per second and the shot peening intensity I will be in the range of 0.47 ⁇ 0.5 mm N.
  • the shot will impart plastic deformation to the coating and thereby close the discontinuous leader regions in the coating.
  • the coating will be left with residual elastic mechanical stresses and the coating will be smooth.
  • the coating is heated at a temperature of 1040 ⁇ 14°C in an inert atmosphere such as a vacuum. After this the density will be found to be almost 100% of the solid metal value and the surface finish will be of the order of 25-35 AA, compared to a typical 50-60 AA of the coating before peening.
  • a coating prepared in the foregoing manner will be contrasted with one prepared according to the techniques of the prior art.
  • the coating is peened according to the prior art with glass beads of SAE J1173 designation GB20 (about 0.2-0.3 mm diameter) using conventional air propulsion, the peening intensity will be about 0.47 N.
  • the coating defects have been closed to a lesser depth than with the invention and the surface finish of the coating will only be improved to about 40-50 AA. This correlates with measurements of the residual compressive stress of titanium alloy test panels using x-ray diffraction.
  • the residual stress state for the larger steel shot of the invention will extend deeper into the workpiece surface.
  • the invention may also be used with plasma spray coatings. Characteristically these coatings have porosity defects more or less uniformly dispersed through the coating.
  • An MCrAIY coating will have a density of about 6.77 grams per cc, about 94% of the theoretical density of the solid alloy.
  • the finish of the coating typically is of the order of 250-370 AA. When a coating is peened in the same manner as described above, it will be found that there will be mechanical closure of many of the defects.
  • the surface of the coating will be significantly smoothed to a finish of about 60-80 AA. Heat treating at 1065-1093°C for four hours in hydrogen or vacuum will somewhat further improve the density of the coating. Measurements show a density of about 7.14 grams per cc or 99% of theoretical is achievable. The result is contrasted with a coating peened using the GB20 glass shot mentioned above. An inferior surface finish of about 100-150 AA will be produced and the coating will not be as dense.
  • the shot size should be of a diameter of 1 mm or greater, preferably between 1-2.5 mm and more preferably between 1.5-2 mm.
  • the shot should be uniform within ⁇ 0.05 mm.
  • the shot peening intensity should be greater than 0.3 N. Up to 0.6 N will be useful.
  • the drop heights should be greater than 0.3 m but less than 6 m, and preferably between 0.5 and 2.0 m.
  • a gas turbine blade 20 has a longitudinal axis 30 and a cross section normal to the axis which has the characteristic cambered shape of an airfoil.
  • the blade has a leading edge 22 and a typically thinner trailing edge 24.
  • To peen such a workpiece it is mounted in a holder 32 adapted to rotate it about its longitudinal axis through a prescribed arc M while the longitudinal axis is held nominally in a plane parallel to the strain line 36 of the stream of shot 34. Shot impacts the surface 28.
  • the workpiece is rotated from a mean position to a certain maximum oblique angle to the shot stream line for each edge as shown in Figure 13.
  • Line 44 is the nominal chord of the airfoil and its position normal to the shot streamline 36 is a reference position for rotation.
  • Lines 41a a and 40a are the center lines for the leading and trailing edges. Referring to the leading edge 22 the airfoil is rotated through angle B from its reference position to second reference position 71 where the center line 41 a is normal to the shot streamline. From position 71 it is then moved through angle +C" to position 73 and then back to position 71, repetitively to peen the upper half of the edge. To peen the other side of the edge the airfoil is turned over on its holder and moved in analogous fashion.
  • the trailing edge 24 is peened by first oscillating it through angle +C' and then turning the part over and oscillating it through angle -C'.
  • both the leading and trailing edge are peened when one side is presented to the shot stream, as the workpiece is first rotated to position 73 and then rotated to position 72.
  • the approximate angle of rotation C for a particular workpiece edge is calculable from the edge radius R, the depth of stressing D desired at the center line of the edge, and the depth q of stressing which the 45° angle shot impacts produce in the workpiece material at a reference location, such as at a point 54 in Figure 14. Namely,

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)

Claims (16)

1. Procédé de traitement de la surface d'une pièce; en vue de réaliser des contraintes compressives résiduelles corréspondant à une intensité de grenaillage d'au moins 0,1 mm N et une finition de surface lisse supérieure à 40 AA par impacts sur la pièce de particules de grenaille sphériques d'une durété supérieure à celle de la pièce, caractérisé en ce que les impacts sont, obtenus à l'aide de particules de grenaille infrangibles, présentant une finition de surface supérieure à 30 AA et des diamètres se situant entre 1 et 2,5 mm qui sont sensiblement uniformes dans des limites d'au moins+ou -0,5%.
2. Procédé selon la revendication 1, caractérisé en ce que les masses de particules de grenaille sont uniformes dans des limites de + ou -16%.
3. Procédé selon la revendication 1, caractérisé en ce que les particules de grenaille ont une vélocité se situant entre 1,4 et 12 mètres par second, vitesse qui est uniforme dans des limites de + ou -4%.
4. Procédé selon la revendication 3, caractérisé en ce que la vitesse se situe entre 2,5 et 7,8 m/second.
5. Procédé selon la revendication 1, caractérisé en ce que les diamètres des particules de grenaille se situent entre 1,5 et 2 mm.
6. Procédé selon la revendication 1,2,3,4, ou 5, caractérisé en ce que l'intensité de grenaillage se situe entre 0,1 et 1,0 mm N, mesure effectué par la méthode d'Almen.
7. Procédé selon la revendication 6, caractérisé en ce que les particules de grenaille présentent des énergies unitaires se situant entre 0,2x 10-4 et 12x10-4 J.
8. Procédé selon la revendication 6, caractérisé en ce que les particules de grenaille sont accélérées par gravité sur une distance de 0,3―6 m.
9. Procédé selon la revendication 5, caractérisé en outre en ce que les particules de grenaille ont une intensité de grenaillage se situant entre 0,20 et 0,50 mm N et une finition de surface d'au moins 15 AA sur une pièce en alliage de titane, l'énergie moyenne unitaire de la grenaille se situant entre 0,6×10-4 et 3x10-4 J.
10. Procédé selon la revendication 9, caractérisé en outre en ce que la grenaille est en acier durci.
11. Procédé selon la revendication 1, caractérisé en outre en ce qu'il consiste à finir la pièce avec une finition de surface inférieure à 40 AA avant grenaillage afin d'obtenir une finition de surface d'au moins 15 AA environ après grenaillage.
12. Procédé selon la revendication 1, caractérisé en ce que la pièce comporte une couche de recouvrement, caractérisée en ce que la surface de la couche de la pièce est soumise à des impacts par des particules de grenaille d'une intensité de grenaillage entre 0,3 et 0,6 mm N.
13. Procédé selon la revendication 13, caractérisé par un traitement thermique de la couche après l'étape qui consiste à soumettre la surface des impacts de particules de grenaille.
14. Procédé selon la revendication 13, caractérisé en ce que la couche est du type MCrAIY caractérisée par un traitement thermique d'environ 1040°C.
15. Procédé selon la revendication 1, caractérisé en ce que les particules de grenaille suivent un trajet sensiblement collimaté et en ce que la pièce présente un bord arrondi s'étendant parallèlement à un axe longitudinal de la pièce, le bord ayant une ligne médiane et une surface tangente normalement à celle-ci, caractérisé en ce qu'il consiste à faire tourner la pièce autour de son axe longitudinal d'un angle suffisant pour présenter une portion du bord au courant de particules de grenaille et insuffisant pour provoquer des impacts normaux à ladite tangente.
16. Procédé selon la revendication 15, dans lequel la pièce présente deux bords opposés, caractérisé par une rotation oscillatoire pour présenter des portions de chaque bord en alternance à la ligne de courant de grenaille.
EP82630084A 1981-09-10 1982-09-08 Procédé de grenaillage et polissage simultanés Expired EP0074918B1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US06/300,727 US4514469A (en) 1981-09-10 1981-09-10 Peened overlay coatings
US300725 1981-09-10
US300727 1981-09-10
US06/300,718 US4426867A (en) 1981-09-10 1981-09-10 Method of peening airfoils and thin edged workpieces
US06/300,725 US4454740A (en) 1981-09-10 1981-09-10 Method for simultaneous peening and smoothing
US300718 1981-09-10

Publications (3)

Publication Number Publication Date
EP0074918A2 EP0074918A2 (fr) 1983-03-23
EP0074918A3 EP0074918A3 (en) 1984-09-05
EP0074918B1 true EP0074918B1 (fr) 1987-07-01

Family

ID=27404758

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82630084A Expired EP0074918B1 (fr) 1981-09-10 1982-09-08 Procédé de grenaillage et polissage simultanés

Country Status (8)

Country Link
EP (1) EP0074918B1 (fr)
AU (1) AU556101B2 (fr)
BR (1) BR8205191A (fr)
DE (1) DE3276662D1 (fr)
IE (1) IE53894B1 (fr)
IL (1) IL66717A (fr)
IN (1) IN157173B (fr)
SG (1) SG69287G (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0318887A1 (fr) * 1987-12-01 1989-06-07 BBC Brown Boveri AG Procédé pour augmenter la résistance à la fatigue et diminuer la tendance à la fissuration à haute température d'une pièce en superalliage à base de nickel durci par dispersion d'oxydes
EP0323388A2 (fr) * 1987-12-24 1989-07-05 United Technologies Corporation Composants revêtus d'un compresseur pour moteur de turbine à gaz
EP0492323A2 (fr) * 1990-12-21 1992-07-01 Mtu Motoren- Und Turbinen-Union MàœNchen Gmbh Procédé de traitement de surfaces de pièces
GB2269393A (en) * 1992-08-08 1994-02-09 Mtu Muenchen Gmbh Treating MCrALZ layers by material-moving machining and then heat treating
US6706331B2 (en) 2000-11-08 2004-03-16 Bhp Steel (Jla) Pty Ltd Cold-formable metal-coated strip

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2708940B1 (fr) * 1993-08-12 1995-09-22 Snecma Procédé de durcissement de pièces métalliques.
US5591009A (en) * 1995-01-17 1997-01-07 General Electric Company Laser shock peened gas turbine engine fan blade edges
IL117347A (en) * 1995-03-06 1999-10-28 Gen Electric Laser shock peened gas turbine engine compressor airfoil edges
US5569018A (en) * 1995-03-06 1996-10-29 General Electric Company Technique to prevent or divert cracks
FR2812286B1 (fr) * 2000-07-28 2003-03-07 Univ Troyes Technologie Procede de generation de nanostructures et dispositif de generation de nanostructures
GB2382641A (en) * 2001-11-28 2003-06-04 Johnson Matthey Plc A refractory furnace block with a surface coated in a platinum alloy
EP1980631A1 (fr) * 2007-04-13 2008-10-15 Siemens Aktiengesellschaft Procédé de grenaillage d'une aube de turbine pour la zone chaude d'une turbine à gaz
US20090098286A1 (en) * 2007-06-11 2009-04-16 Honeywell International, Inc. Method for forming bond coats for thermal barrier coatings on turbine engine components
CN112643554B (zh) * 2020-12-22 2022-07-05 中船重工龙江广瀚燃气轮机有限公司 一种叶片液体喷丸控制方法
CN113322468B (zh) * 2021-05-25 2023-03-28 合肥学院 一种提高钛锆基合金耐磨性的表面强化方法
CN114657490B (zh) * 2022-03-22 2022-11-01 合肥学院 一种钛锆基合金表面处理工艺及喷丸强化装置

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT267567B (de) * 1965-12-03 1969-01-10 Knapsack Ag Siziliumhaltiges Stahlschrot als Strahlmittel
US3542530A (en) * 1968-05-23 1970-11-24 United Aircraft Corp Nickel or cobalt base with a coating containing iron chromium and aluminum
US3705511A (en) * 1969-10-17 1972-12-12 Avco Corp Low penetration ball forming process
US4287740A (en) * 1978-09-12 1981-09-08 Rockwell International Corporation Method of increasing the fatigue life of titanium alloy parts
US4217769A (en) * 1978-10-10 1980-08-19 Consolidated Papers, Inc. Method of forming a coating application roll
US4222793A (en) * 1979-03-06 1980-09-16 General Motors Corporation High stress nodular iron gears and method of making same

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
MACHINERY AND PRODUCTION ENGINEERING, vol. 129, 4th August 1976, pages 98-102, Burgess Hill, US A. DART: "Improving fatigue strength of metals - 1" *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0318887A1 (fr) * 1987-12-01 1989-06-07 BBC Brown Boveri AG Procédé pour augmenter la résistance à la fatigue et diminuer la tendance à la fissuration à haute température d'une pièce en superalliage à base de nickel durci par dispersion d'oxydes
CH676126A5 (fr) * 1987-12-01 1990-12-14 Bbc Brown Boveri & Cie
EP0323388A2 (fr) * 1987-12-24 1989-07-05 United Technologies Corporation Composants revêtus d'un compresseur pour moteur de turbine à gaz
EP0323388A3 (en) * 1987-12-24 1990-07-11 United Technologies Corporation Coated gas turbine engine compressor components
EP0492323A2 (fr) * 1990-12-21 1992-07-01 Mtu Motoren- Und Turbinen-Union MàœNchen Gmbh Procédé de traitement de surfaces de pièces
EP0492323A3 (en) * 1990-12-21 1992-10-07 Mtu Muenchen Gmbh Method for the surface-treatment of parts
GB2269393A (en) * 1992-08-08 1994-02-09 Mtu Muenchen Gmbh Treating MCrALZ layers by material-moving machining and then heat treating
GB2269393B (en) * 1992-08-08 1995-08-09 Mtu Muenchen Gmbh Method of treating MCrAlZ layers
US6706331B2 (en) 2000-11-08 2004-03-16 Bhp Steel (Jla) Pty Ltd Cold-formable metal-coated strip

Also Published As

Publication number Publication date
IL66717A (en) 1985-07-31
SG69287G (en) 1988-02-19
IL66717A0 (en) 1982-12-31
EP0074918A3 (en) 1984-09-05
IE822161L (en) 1983-03-10
BR8205191A (pt) 1983-08-16
IE53894B1 (en) 1989-04-12
DE3276662D1 (en) 1987-08-06
AU556101B2 (en) 1986-10-23
AU8813982A (en) 1983-03-17
EP0074918A2 (fr) 1983-03-23
IN157173B (fr) 1986-02-01

Similar Documents

Publication Publication Date Title
US4454740A (en) Method for simultaneous peening and smoothing
EP0074918B1 (fr) Procédé de grenaillage et polissage simultanés
CA1192387A (fr) Methode de grenaillage de profils aerodynamiques et de pieces a rives amincies
US4428213A (en) Duplex peening and smoothing process
CA1191672A (fr) Dispositif de grenaillage
US20030088980A1 (en) Method for correcting defects in a workpiece
MX2008011226A (es) Proceso para la reparacion y restauracion de componentes tensionados dinamicamente que comprenden aleaciones de aluminio para aplicaciones de avion.
CN1372502A (zh) 部件的表面处理方法及装置
JP5776991B2 (ja) 硬化防食鋼板部材の表面仕上げ方法
EP0492323B1 (fr) Procédé de traitement de surfaces de pièces
US20100119375A1 (en) Pre-Coating Burnishing of Erosion Coated Parts
Kulkarni et al. Investigation of shot peening as a forming process for aircraft wing skins
US5090870A (en) Method for fluent mass surface texturing a turbine vane
US5120613A (en) Pocess for increasing the resistance to corrosion and erosion of a vane of a rotating heat engine
Yao et al. Fretting fatigue life improvement of nickel-based superalloy GH4169 dovetail slots by deflecting abrasive waterjet peening process
JP3651665B2 (ja) プレス成形性および塗装後鮮映性に優れた冷延鋼板
CA1196486A (fr) Methode de grenaillage et de lissage en simultane
Kostilnik Shot peening
Griffiths et al. A definition of the topography of grit-blasted surfaces for plasma sprayed alumina coatings
JPS62224405A (ja) 冷延鋼板の製造方法
Korzynski Predicting the height of uneven surface after ball-peening machining
Rao et al. Effect of surface configuration during solid particle impingement erosion
Heaton Shot peening
Loersch et al. Simultaneous Peening and Smoothing of Part-Surfaces for Aerospace Applications
Rao et al. A study of the effect of solid particle impact and particle shape on the erosion morphology of ductile metals

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): BE CH DE FR GB IT LI NL SE

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Designated state(s): BE CH DE FR GB IT LI NL SE

17P Request for examination filed

Effective date: 19841212

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): BE CH DE FR GB IT LI NL SE

ET Fr: translation filed
REF Corresponds to:

Ref document number: 3276662

Country of ref document: DE

Date of ref document: 19870806

ITF It: translation for a ep patent filed

Owner name: UFFICIO BREVETTI RICCARDI & C.

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
ITTA It: last paid annual fee
EAL Se: european patent in force in sweden

Ref document number: 82630084.0

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: CH

Payment date: 19950814

Year of fee payment: 14

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: BE

Payment date: 19950824

Year of fee payment: 14

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Effective date: 19960930

Ref country code: CH

Effective date: 19960930

Ref country code: BE

Effective date: 19960930

BERE Be: lapsed

Owner name: UNITED TECHNOLOGIES CORP.

Effective date: 19960930

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19990807

Year of fee payment: 18

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 19990816

Year of fee payment: 18

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19990818

Year of fee payment: 18

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19990819

Year of fee payment: 18

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19990825

Year of fee payment: 18

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20000908

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY

Effective date: 20000929

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20010401

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20000908

EUG Se: european patent has lapsed

Ref document number: 82630084.0

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20010531

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee

Effective date: 20010401

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20010601

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST