Method for preparing a surface before thermal spray-coating

Abstract

The invention relates to a method for preparing the surface of a substrate (100) for the purpose of accepting and holding a coating sprayed by a plasma torch. Said method includes a machining phase and is characterized that it includes the following phases: producing, by means of a machining tool (200), at least one groove having at least one angled edge; offsetting the tool (200) by moving the tool relative to the surface of the substrate (100) in a direction perpendicular to the longitudinal axis of the groove and along a path shorter than the projected length of the angled edge; and using said tool (200) on the angled edge of the groove such as to subject said edge to stress and create another offset groove, and so on and so forth, such that the tool (200) irreversibly changes the shape of the ribs (111, 112, 113, 114) finally obtained between each groove, and said ribs adopt undercut surfaces.

Claims

1. Method for preparing the surface of a substrate (100) for the purpose of accepting and holding a coating sprayed by a plasma torch, said method being of the type of the one comprising a machining phase, CHARACTERIZED IN THAT it comprises the following phases: producing, by means of a machine tool (200) at least one groove with at least one angled edge, offsetting the tool (200), by moving the tool relative to the surface of the substrate (100), according to a direction perpendicular to the longitudinal axis of the groove and along a path shorter than the projected length of the angled edge, using said tool (200) on the angled edge of the groove in such a way as to subject this edge to stress and create another offset groove and so on and so forth such that the ribs (111, 112, 113, 114) finally obtained between each groove are irreversibly deformed under the action of the tool (200) and adopt undercut surfaces.

2. Method according to claim 1, CHARACTERIZED IN THAT the tool (200) is a milling tool set into rotation with respect to the part.

3. Method according to claim 1, CHARACTERIZED IN THAT the tool (200) is a milling tool having a plurality of cutting edges adopting a substantially triangular profile.

4. Method according to claim 2, CHARACTERIZED IN THAT the tool (200) is a comb threading tool.

5. Method according to claim 2, CHARACTERIZED IN THAT the tool (200) follows a path by helical interpolation by means of a numerical-controlled machine tool.

6. Method according to claim 4, CHARACTERIZED IN THAT the comb tool (200) produces successive machinings according to a pitch corresponding to a division of the pitch for which it is preformed.

7. Method according to claim 6, CHARACTERIZED IN THAT the comb tool (200) produces successive machinings according to a pitch corresponding to a division by 4 of the pitch for which it is preformed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagrammatical drawing of a comb threading tool that is to be applied on the surface of a bore that is to receive a coating via plasma projection;

(2) FIG. 2 is a diagrammatical drawing of a detailed cross-section view of the tool and of the machining carried out on the surface of the bore by the tool;

(3) FIG. 3 is a diagrammatical cross-section drawing of the tool during machining according to a first offset of the tool,

(4) FIG. 4 is a diagrammatical detailed cross-section drawing of the tool and of the machining carried out according to the first offset;

(5) FIG. 5 is a diagrammatical cross-section drawing of the tool during machining according to a second offset of the tool,

(6) FIG. 6 is a diagrammatical detailed cross-section drawing of the tool and of the machining carried out according to the second offset;

(7) FIG. 7 is a diagrammatical cross-section drawing of the tool during machining according to a third offset of the tool,

(8) FIG. 8 is a diagrammatical detailed cross-section drawing of the tool and of the machining carried out according to the third offset;

EMBODIMENT DESCRIPTION

(9) As shown in the drawing in FIG. 1, the method for preparing the surface of the bore 100 for the purpose of accepting and holding a metal coating is implemented by a comb tool 200 driven in rotation according to the arrow F1 and which will come into contact with the surface of the bore 100 according to a first position then be successively axially offset according to the arrow F2 and return to contact with the bore in accordance with the invention.

(10) The succession of FIGS. 2 to 8 shows the detail of the succession of the machinings of 5 triangular shapes 210, 220, 230, 240, 250 constituting a portion of the cutting edges of the tool 200.

(11) As shown in the drawing in FIG. 2, in accordance with conventional machining, the machining path of the tool in rotation 200, path shown by the double-arrow F3, conducted the shapes 210, 220, 230, 240 and 250 to the production by removal of material of grooves and of complementary ribs 110, 120, 130, 140, 150 with a substantially identical profile and according to a pitch P corresponding to the pitch P defined by the shapes of the tool.

(12) As shown in the drawing in FIG. 3, an offset corresponding to a quarter of the pitch P and an equivalent machining path drive the shapes 210, 220, 230, 240, 250 to machine the bore by coming into contact with the latter on the angled surfaces of the ribs 110, 120, 130, 140, 150 already produced by creating two smaller ribs. In accordance with the invention, this offset constitutes a path shorter than the projected length of the angled edge of the groove, with the principle being to return to create a machining on the angled surface that has just been produced.

(13) Taking the example of rib 110, for each first rib machined, a smaller rib 111 and a larger rib 110 result from this new machining.

(14) As shown in the drawings in FIGS. 3 and 4, the stress exerted during machining by the triangular shape 210 on the angled machined plane in the preceding cutting machining 200 and the reduction of the foot of the rib lead to the plastic deformation of the two ribs 111, 110 created. The deformation of the small rib 111 is greater than the deformation of the larger rib 110 and has undercut surfaces. The same applies to all of the ribs.

(15) As shown in the drawings in FIGS. 5 and 6, an equivalent additional offset and a machining path lead to the machining of the rib 110 and to the creation of: a second small rib 112 with a size substantially equivalent to the first small rib 111 but with a more pronounced deformation due to the deformation of the rib 110 in the preceding machining, a third larger rib 110 which itself has been subject to a deformation.

(16) Finally, as shown in the drawings in FIGS. 7 and 8, an equivalent additional offset and machining path lead to the machining of the rib 110 and to the creation of: additional smaller ribs 113 and 114 with a size substantially equivalent to the first two 111 and 112 but with a more pronounced deformation in particular for the fourth 114 due to the deformation of the rib 110 but also the creation of the rib 211 in the vicinity.

(17) As such, unexpectedly, it appears that the succession of machinings produced in these conditions does not provoke the true reproduction of an under-dimensioned version of the profiles of the shapes of the cutting tool but the deformation of the profiles and the creation of undercut shapes allowing for the accepting and the mechanical blocking sought for a coating via thermal spray-coating. According to a test, this deformation was observed on a surface of a molded aluminum substrate.

(18) It is understood that the method, which has just been described and shown hereinabove, was described and shown as a disclosure rather than as a limitation. Of course, various arrangements, modifications and improvements can be made to the example hereinabove, without however leaving the scope of the invention.