A coating process involving machining a notch to minimize metallurgical defects

Abstract

This process of adding filler material to a hardfacing part comprises the following steps: - Machining a notch (13) in a surface (15) of a workpiece (17); - Performing a first hardfacing pass (19) on the workpiece (17), the first end (23) of which is located inside the notch (13); and - Forming a second hardfacing pass (27) on the workpiece (17), covering the first end (23) of the first hardfacing pass (19), the second hardfacing pass (27) being in contact on one side with the surface (15) of the workpiece (17) and on the other side with the first hardfacing pass (19). Figure for the abbreviation: Fig. 3

Description

Title of the invention: Coating method with machining of a notch minimizing metallurgical defects. Technical field

[0001] The present invention relates to the reloading with overlap of two reloading passes.

[0002] In particular, the present invention relates to the reduction of metallurgical defects due to overlaying. Previous techniques

[0003] A schematic cross-sectional view of an example of reloading with overlap according to the prior art is shown in [Fig.1].

[0004] Unlike welding, which allows parts to be joined together, hardfacing consists of covering a surface with one or more layers of a filler material.

[0005] During a hardfacing process with overlapping, a part 1 is covered with a first hardfacing pass 3, and then a second hardfacing pass 5 covers the first hardfacing pass 3. A hardfacing pass is formed by a bead of filler material. The two hardfacing passes consist of two separate beads of filler material or of a single bead of filler material that has formed a loop and whose end overlaps the beginning.

[0006] However, at the location where the first hardfacing pass 3 comes into contact with the second hardfacing pass 5, metallurgical defects appear at the junction of the two passes 3 and 5, for example porosities 7, which impairs the mechanical properties and performance.

[0007] Moreover, since the change of direction of the second reloading pass 5 is particularly abrupt, shrinkage cavities 9 appear on the surface of the second reloading pass 5 also during the solidification of said second reloading pass 5. These defects 7 and 9 are volumetric defects such as porosities, shrinkage cavities or even crack initiations; they are not, however, microstructural defects. Description of the invention

[0008] The present invention therefore aims to overcome the aforementioned disadvantages and to provide a resurfacing with a coating that does not present any metallurgical defects.

[0009] The present invention relates to a method of resurfacing by adding a filler material, the method comprising the following steps:

[0010] - Machining a notch in a surface of a part;

[0011] - Performing a first reloading pass on the part, of which a first The end is located inside the notch; and

[0012] - Formation on the part of a second reloading pass covering the first end of the first reloading pass, the second reloading pass being on one side in contact with the surface of the part and on the other side in contact with the first reloading pass.

[0013] Thus, the presence of the notch makes the formation of the second cladding pass on the first cladding pass less abrupt, and no porosity or shrinkage cavities appear during such cladding. The present invention makes it possible, in particular, to avoid sharp angles at the overlap, preventing the generation of volumetric defects.

[0014] Preferably, any welding process is excluded from the scope of the present invention, which therefore only relates to a cladding process.

[0015] Advantageously, the depth of the notch is determined by the height of the first end of the first reloading pass. The notch is, for example, deeper than half the height of the first reloading pass.

[0016] Advantageously, the notch is less deep than the height of the first reloading pass.

[0017] According to one embodiment, the length of the notch along the direction of the first reloading pass is greater than the length of the slope of establishment of the stabilized regime of the height of the first reloading pass.

[0018] The length of the slope during which the stabilized height of the first hardening pass is established, namely the length during which the first pass has not reached its nominal height, is approximately equal to the diameter of the first pass, plus or minus 50%. Thus, in a particular embodiment, the length of the notch along the direction of the first hardening pass is greater than the diameter of the first hardening pass.

[0019] Advantageously, the notch, according to the direction of the first reloading pass, has a section defined by a first slope and a second slope, each starting from the surface of the part and meeting by a rounded end at the bottom of the notch.

[0020] In a particular embodiment, the first slope of the notch has an angle with the surface of the part less than 30°, preferably less than 20°, and in which the second slope has an angle with the surface of the part greater than the angle between the first slope and the surface of the part and less than 60°.

[0021] Advantageously, the rounding at the bottom of the notch has a radius of curvature greater than half the height of the first reloading pass, preferably greater than the height of the first reloading pass.

[0022] In a particular embodiment, the first reloading pass and the second reloading pass are two portions of one and the same looped cord, the first end of which is located inside the notch, the looped cord overlapping itself above the notch.

[0023] Advantageously, the part and the first reloading pass and the second reloading pass comprise a metal alloy, preferably an alloy comprising steel and / or aluminum, and / or nickel and / or titanium and / or chromium and / or cobalt.

[0024] For example, the steps of carrying out the first reloading pass and forming the second reloading pass are implemented by single-cord reloading. Brief description of the drawings

[0025] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0026] [Fig.1] is a schematic cross-sectional view of an example of resurfacing with overlapping according to the prior art;

[0027] [Fig.2] is a schematic representation of the steps in the reloading process according to the invention; and

[0028] [Fig.3] is a schematic cross-sectional view of the result of the reloading process with overlap according to [Fig.2].

[0029] Detailed description of at least one embodiment

[0030] The steps of the reloading process with recoating according to the invention have been schematically represented on [Fig.2].

[0031] In addition, a schematic cross-sectional view of the result obtained following the implementation of said reloading process has been shown in [Fig.3].

[0032] For the implementation of the process according to the invention, a machining step 11 of a notch 13 in a surface 15 of a part 17 is carried out first.

[0033] Then a first reloading pass 19 is carried out on part 17 according to a step 21. The first reloading pass has a first end 23 located inside the notch 13.

[0034] Finally, a step 25 of formation is carried out on the part 17 of a second reloading pass 27 covering the first end 23 of the first reloading pass 19, the second reloading pass 27 being on one side in contact with the surface 15 of the part 17 and on the other side in contact with the first reloading pass 19.

[0035] The implementation of the preceding steps is carried out in a particular direction, in particular the direction followed by the cut of [Fig.3].

[0036] In addition, steps 21 and 25 of carrying out the first reloading pass 19 and of forming the second reloading pass 27 are for example implemented by single-cord reloading.

[0037] In a particular embodiment, the first reloading pass 19 and the second reloading pass 27 are two portions of one and the same looped cord, the first end 23 of which is located inside the notch 13, the looped cord overlapping itself above the notch 13, allowing the reloading of parts with a circular cross-section such as a housing for example.

[0038] Advantageously, the first reloading pass 19 and the second reloading pass 27 each comprise a metal alloy, preferably an alloy comprising steel and / or aluminum, and / or nickel and / or titanium and / or chromium and / or cobalt.

[0039] Advantageously, part 17 is made of a metal alloy, preferably an alloy comprising steel and / or aluminum and / or nickel and / or titanium and / or chromium and / or cobalt.

[0040] The notch 13 can be machined in a particular way in order to minimize the number of volumetric defects in the reloading passes performed.

[0041] In particular, the notch 13 preferably has a depth P greater than half the height D of the first reloading pass 19.

[0042] Height D is understood to mean the average height, or nominal height, of the cross-section of the first hardfacing pass, even if the cross-section of said first hardfacing pass 19 is not perfectly circular. The cross-section of a hardfacing pass is measured in the direction orthogonal to the surface of the part 17.

[0043] According to one embodiment, the length L of the notch 13 along the direction of execution of the first reloading pass 19 is greater than the height D of the first reloading pass 19.

[0044] Furthermore, the shape of the notch 13 is defined according to the direction of the first reloading pass 19. The notch 13 thus has a cross-section defined by a first slope 29 and a second slope 31 each starting from the surface 15 of the part 17 and joining by a rounded 33 at the bottom of the notch 13. The first slope 29 and the second slope 31 are preferentially tangent to the rounded 33, also called the connecting radius.

[0045] In a particular embodiment, the first slope 29 has an angle A with the surface 15 of the part 17 less than 30°, preferably less than 20°, even more preferably less than 10°.

[0046] The second slope 31 has an angle B with the surface 15 of the part 17 greater than the angle A between the first slope 29 and the surface 15 of the part 17, and less than 60°.

[0047] In a particular embodiment, the rounded 33 at the bottom of the notch 13 has a radius of curvature greater than half the height D of the first reloading pass 19, preferably greater than the height D of the first reloading pass 19.

Claims

Demands

1. A method for adding a filler material to build up a surface, characterized in that it comprises the following steps: - A machining step (11) of a notch (13) in a surface (15) of a part (17); - A step of making (21) on the part (17) a first build-up pass (19) of which a first end (23) is located inside the notch (13); and - A step of forming (25) on the part (17) a second build-up pass (27) covering the first end (23) of the first build-up pass (19), the second build-up pass (27) being on one side in contact with the surface (15) of the part (17) and on the other side in contact with the first build-up pass (19).

2. Method according to claim 1, wherein the notch (13) has a depth (P) greater than half the height (D) of the first reloading pass (19).

3. A method according to any one of claims 1 and 2, wherein the notch (13) has a depth (P) less than the height (D) of the first reloading pass (19).

4. A method according to any one of claims 1 to 3, wherein the length (L) of the notch (13) along the direction of the first reloading pass (19) is greater than the length of the slope of establishment of the stabilized regime of the height of the first reloading pass.

5. A method according to any one of claims 1 to 4, wherein the notch (13), along the direction of the first reloading pass (19), has a section defined by a first slope (29) and a second slope (31) each starting from the surface (15) of the part (17) and joining by a rounded end (33) at the bottom of the notch (13).

6. A method according to claim 5, wherein the first slope (29) of the notch has an angle (A) with the surface (15) of the part (17) less than 30°, preferably less than 20°, and wherein the second slope (31) has an angle (B) with the surface (15) of the part (17) greater than the angle (A) between the first slope (29) and the surface (15) of the part (17) and less than 60°.

7. A method according to any one of claims 5 and 6, wherein the rounding (33) at the bottom of the notch (13) has a radius of curvature greater than half the height (D) of the first reloading pass (19), preferably greater than the height (D) of the first reloading pass (19).

8. A method according to any one of claims 1 to 7, wherein the first reloading pass (19) and the second reloading pass (27) are two portions of a single looped cord, the first end (23) of which is located inside the notch (13), the looped cord overlapping itself above the notch (13).

9. A method according to any one of claims 1 to 8, wherein the part (17) and the first hardfacing pass (19) and the second hardfacing pass (27) comprise a metal alloy, preferably an alloy comprising steel and / or aluminum, and / or nickel and / or titanium and / or chromium and / or cobalt.

10. A method according to any one of claims 1 to 9, wherein the steps (21; 25) of carrying out the first reloading pass (19) and of forming the second reloading pass (27) are carried out by single-bead reloading.

Images