FR2594851A1 - METAL PARTS WITH AT LEAST SIDE OF AT LEAST ONE AREA OF WEAR-RESISTANT ZONES - Google Patents

Abstract

The invention relates to metal parts at least one face of which has at least one region of wear-resistant zones. These parts consist of a controlled distribution of areas hardened by localized melting effect, characterized in that said areas, whatever their length and shape, have a width and a depth of between 3 and 150 μm and that the surface fraction of areas for every mm ** 2 of a region is between 5 and 60%. These parts can be used in the manufacture, in particular of liners and pistons of engines, of valve seats, of brake drums and discs, of toothed transmission pulleys, of dies, of gears, of bearings, of bearing seats. 'drive shafts, ball bearings and various electrical parts for sliding contacts. (CF DRAWING IN BOPI)

Description

METAL PIECES WITH AT LEAST SIDE OF AT LEAST ONE AREA

OF ZONES RESISTANT TO WEAR

  The present invention relates to metal parts of which one face

  at least has at least one region of wear-resistant zones.

PRESENTATION OF THE PROBLEM

  Those skilled in the art know that the metal parts subjected to friction must have technological characteristics such that, in particular, the wear resistance and the resistance to galling at least on their "active" face, that is, to say that which is in contact with the

  antagonist piece. In most cases, these features are not necessary.

  only in areas representing only a portion of

  face, and in well-localized areas of said regions.

  These areas generally result from super-hardening treatment.

  parts obtained by different means.

PRIOR ART

  For example, the French patent 2,371,520 describes a

  process of a given exposed region of an aluminum article

  nium or one of its alloys in the presence or absence of an alloying agent, with a laser beam or a high energy electron beam (at least 10,000 watts / cm2) and with a diameter of between 250 and 1250 μm, of

  to be able to heat the article in a first zone and to

  in a second zone within said first zone: a fine-grained structure is thus created at least in said zone, for the purpose, inter alia, of improving the wear resistance and eliminating

  or to reduce the deformations resulting from the treatment.

  Claim 24 of this patent states that "said beam is moved along a plurality of separate and spaced paths so as to affect

  areas forming spaced regions on the exposed surface of said article.

  Similarly, French Patent 2,367,117 claims "a method of treating

  A metallic surface of a component is characterized in that it consists in heat-treating only bearing areas to modify their metallurgical properties and improve their wear resistance. "According to a particular example of this process , the treatment is applied to a carburized hardened cast iron cylinder liner and consists in directing on it a laser emitting a beam such that it forms

a point with a diameter of 3,000 μm.

  Japanese Patent Application Publication No. 59 212 572 teaches

  also a hardening treatment process of the integrated surface

  of an internal combustion engine cylinder by means of a laser

  in which the surface ratio of the untreated zones to the treated zones

  is preferably between 10 and 70% and the size of the zones

processed is several mm.

  These documents thus teach that areas capable of friction can be obtained on parts by thermally treating their surface.

  to locally obtain areas of a width exceeding 250 μm.

  The applicant, seeking to apply such teachings, has found that it is possible, of course, to obtain localized hardening at the treatment zones, but that this hardening is accompanied by localized fusion, on the one hand, by deformation of the part as it required reworking before use, on the other hand, sometimes

  cracks and fatigue crack initiation due to

  perfected by the local overheating resulting from the treatment

ment.

PURPOSE OF THE INVENTION

  Therefore, the request has sought to develop metal parts of which at least one side is treated by thermal melting effect so as to develop at least a region of areas resistant to wear and friction but such that they contain very few surface stresses likely to develop cracks or other degradation during their use and also as they

  can be used raw for processing, that is to say without success.

  swimming, expensive and delicate operation on hardened parts and which, by its thermal and mechanical effects, can modify the structure of the zone

  treated and, consequently, its tribological characteristics.

SUMMARY OF THE INVENTION

  According to the invention, the metal parts with at least one face present

  at least one wear-resistant region formed by a

  Controlled partition of localized melting hardened zones are characterized in that said zones, irrespective of their length and shape, have a width and a depth of between 3 and

  am and that the area fraction of the areas for each mm2 of a

  is between 5 and 60 Z. Thus, do the active faces of the invented

  surface area, and in areas suitably selected according to the

  age, hardened areas that meet both

  following ticks: - on the one hand, a more or less elongated shape, but a very small width and depth compared to the parts of the prior art - on the other hand, a fine distribution of said zones, since for each mm2 of surface belonging to a region, they represent 5 to 60% of said area, that is to say that they are spaced apart from each other.

  others by a distance of less than 1 mm.

  In addition to these features, it was found to be interesting when

  areas intersect to limit the surface area of

  2, said zones for each mm of a region at 50% of the area

total areas.

  Under these conditions, it is observed that, in addition to the significant increase in the wear resistance caused by the presence of hardened zones, the deformation stresses caused by the melting-resolidification at the zone level were much lower than those observed on the zones. areas of greater width and depth or overlapping

  more broadly the surface or intertwining more fre-

quente.

  Similarly, we note that the differences in ratings between zones and

  interzonal spaces do not exceed 10 pm, which avoids any success in

  parts before use. In other words, the treatment modifies little the geometrical profile of the treated part and involves only a slight modification of the roughness. Furthermore, the presence of spaces between the zones significantly improves the ability of the parts to friction by creating on the surface and on a thin scale an alternation of hardened areas and soft spaces, very effective disposition generally in wear resistance by adhesion, fatigue

  or abrasion and also effective in friction since the spaces

  soft terzones are traps for lubricants or even traps for

wear debris.

  However, in the range of width and depth of

  sold, it was noted that it was better to stick to

  their between 010 and 100 pm for best results.

  The invention itself does not impose: - uniformity of shape of the zones: in the case of a zone of any shape, the notion of width quoted above can be defined as being twice the dimension 1/2 which leads in techniques

  so-called squelletization used in image analysis to

zone,

  - nor a regular layout of the surface areas.

  In fact, the invention involves the statistical idea of

  only to reduce the width and depth of the zones and to separate them, the distribution at the mm2 scale and the shape of the zones having a second-order effect with respect to the width-depth and surface fraction effect. However, for the sake of convenience of creating these areas on the surface of the parts, the invention also encompasses the zones regularly arranged on the surface of the parts in the form of periodic or quasi-periodic networks of strips whose width and depth are

  obviously between 3 and 150 pun.

  Thus, the zones can be arranged in the form of continuous strips separated from each other by a distance between

  and 1000 μm, these bands having either any direction or

  at least one network of parallel bands. But these zones can also be arranged in the form of discrete strips separated along their length and from each other by a distance of

  between 20 and 1000 PM; these bands having, as before, either a direct

  whatever is at least one network of parallel bands.

  The invention applies in particular to any alloy, in particular aluminum

  nium, whose tribological properties are likely to be improved

  by a superficial fusion treatment. It also applies

  to all parts where the zones consist of a molten base metal alloy with a filler or a feed compound such as

  that said alloy has better tribological properties than the

  base. This element may be, for example, iron or nickel,

  when the base metal is an aluminum alloy.

  Zones meeting the characteristics of the invention may be obtained

  held by any process which makes it possible to locally modify the nature or the structure of the surface of the part to a shallow depth and a small width so as to confer on it by thermal effect and / or

  chemical better rubbing ability.

  We can notably mention the use of high energy radiation

  such as electron beams and laser radiation suitably

  focused in such a way as to create by fusion areas of width and

depth less than 150 pum.

  Obtaining axial, circular or helical strips or any other shape can be easily achieved by controlling the relative displacement

  of the part and the beam via a microprocessor.

  For example, with a conventional 18-watt argon laser beam focused enough to achieve power density

6 2

  greater than 1.10 watts / cm 2, it has been possible to realize on the surface of aluminum-silicon alloy parts a square-meshed network formed of strips of width 30 μm separated from each other by a distance of 100 μm and this by exposing the parts to the beam action for less than 1. 10-1 second and moving the beam relative to the

  to describe a series of parallel trajectories

  in two perpendicular directions. But we can also use

  energy sources capable of emitting a large number of

  This allows a more practical realization of the network.

  In this way, a set of small processed areas (width <150 μm) separated from each other and formed one

  surface made of a hard material embedded in a softer matrix

  the. The pieces thus treated showed only a minor deformation of the surface profile, this avoiding reworking; their application to an aluminum alloy motor jacket did not lead to any deterioration

  by release of constraints and their tribological behavior

  plunger / segment tact was better than that of shirts which any

  the surface had been treated with beams creating areas of

3000 pm.

  The invention can be illustrated with the aid of the accompanying drawings which

  with regard to Figures 1, 2 and 3, different

  zones produced according to the invention on a region of a face

  active part of a room while Figure 4 refers to a microphoto-

  graphing a portion of a region of a room according to the invention and FIGS. 5, 6 and 7 to micrographic sections of rooms according to the art

  front (Figures 5 and 7) and according to the invention (Figure 6).

More precisely:

  FIG. 1 shows zones (1) of any shape and width

  distributed in any way but all of which have a width of between 10 and 100 μm and a surface fraction for each mm 2

  surface area of between 5 and 60%.

  FIG. 2 shows zones arranged regularly in a square-mesh network consisting of strips (2) with a width of

  40 pm spaced from each other 360um.

  FIG. 3 represents point zones (3) with a dimension of

  pm spaced from each other by 100 -pm.

  FIG. 4 is a microphotograph at 100 magnification of zones distributed in 40 μm wide bands spaced from each other by 200 μm and intersecting at right angles and which are obtained

  on aluminum alloy parts of the type A-S17U4G (Silicon 17% -

  4% copper - <1% magnesium - aluminum balance).

  Figures 5, 6 and 7 will be discussed in the following discussion of the example.

EXAMPLE OF APPLICATION

  Parts made of A-S5U3 (that is to say containing by weight 5% of silicon, 3% of copper and the balance of aluminum and impurities) and of A-S17U4G (17% Si, 4% Cu, <1 % Mg) developed in the same way were divided into two lots numbered 1 and 2, both including both types of alloy.

  Lot 1 was subjected to a laser treatment to obtain the following zones:

  prior art and Lot 2 to another laser treatment to obtain

zones according to the invention.

  The conditions of these treatments are as follows: Laser beam Power (watts) 25. Beam width (pm) Power density (watts / cm) Treatment time (sec) Width of the treated area (pm) Depth of the treated area (Fm) Lot 1 CO2 2,5xo106 6/100

* 3000

  Lot 2 Ar 7xl o6 1/40 M20 The following observations have been made: From the relief point of view: on lot 1 (fig 5), which shows, in section and at magnification, an area (4), a relief is observed macroscopically extending over the entire width of the zone and whose amplitude reaches 100 μm, which

requires to succeed the room.

  on the contrary, on lot 2 (figure 6) which represents, seen in section, and

  at magnification 1000 a zone (5), no macroscopic relief is observed.

  Spades. Only the microroughness is slightly affected but it does not

no re-manufacturing.

  In these figures 5 and 6, there is also a radical change in the structure of

  which allows a precise location of the area and the measurement of its dimensions. Of the 2 lots, a Vickers hardness greater than 200 was measured in

area and 80 between areas.

  Consequently, the parts according to the invention and which therefore have areas of small width and shallow depth have a degree of deformation of the surface profile such that it is no longer necessary to machine them. Other pieces of the same type were previously coated with an electrolysis iron film in such a quantity as to allow after fusion

  to achieve on the surface an alloy with 15% iron.

  These pieces were shared equally in 2 lots that suffered the same

  than those described above, except as regards the

position of the treated areas.

  Indeed, the surface of the parts of lot 1 was treated according to

  unidirectional parallels overlapping (lot IA) or not (lot lB: distance between bands 2000 pm) while that of lot 2 was treated

  following a network of parallel bands intersecting at right angles and

  from each other by 200 μm.

  Micrographic examination of the surfaces has shown that in some cases the

  treated areas of lots IA and IB showed fissures (6) (Fig.

  7), while those in Lot 2 (Figure 6) did not have one.

  In another series of tests, iron was replaced by a galva-

  nickel in order to carry out on the surface after melting a 10% nickel alloy and the parts of the two batches were subjected to measurements of

  friction-wear using the CAMERON-PLINT tribometer.

  This tribometer consists of a chromed cast iron segment which presses against the surface to be controlled and which is reciprocated so as to simulate approximately the friction that occurs between the segments inserted in the piston and the jacket of an engine. internal combustion. In this case, the backing load was 100 N, the room temperature was 100 C, the frequency of the movement was 12 Hz and the test time was 30 minutes. The surface was previously lubricated with an oil of the type

Neutral 150.

  Parts of lot 1 deteriorated rapidly (large debris detachment> 1 μm from the treated surface). It was the same

chrome cast iron segment.

  As for the parts of lot 2, they did not give rise to any deterioration

  visible or measurable weight loss.

  The present invention finds its application in the manufacture of parts intended to be subjected to friction such as for example

  mechanical parts (engine liners and pistons, wheelchairs)

  pes, drums and brake discs, toothed transmission pulleys,

  dies, gears, bushings, driving shafts, rollers

  ball bearings, etc.) and electrical contact parts

  combines friction and the passage of electric current (connectivity,

  sliding tact, electric motor collector, etc ...).

  It has been developed on aluminum alloys, but can also be

  apply to other metallic materials and alloys: steel, copper, zirconium, titanium, nickel. It has been verified on

  some examples: nickel, copper, titanium.

Claims (12)

  1. Metal parts with at least one surface surface having at least one wear-resistant region constituted by a controlled distribution of the hardened zones by localized melting effect, characterized in that these zones, whatever their length and their shape, have a width and a depth of between 3 and 150 μm and that the area fraction for each mm 2 of a region is between 5 and 6%. 2. Metal parts according to claim I characterized in that   when the zones intersect, the surface fraction of   areas for each mm2 of a region is less than 50% the total area of the areas.   3. Metal parts according to claim I characterized in that the areas have a width and a depth between 10 and 100 Am. 4. Metal parts according to claim I characterized in that the zones are arranged in the form of continuous strips of any direction and separated from each other by a distance between between 20 and 1000 jum.   5. Metal parts according to claim 4, characterized in that   the zones are arranged in the form of at least one network of pa-   rallèles. 6. Metal parts according to claim I characterized in that the zones are arranged in the form of discontinuous strips, of any direction, separated along their length and from each other by   a distance of between 20 and 1000 μm.   7. Metal parts according to claim 6, characterized in that   the zones are arranged in the form of at least one network of pa-   rallèles. 8. Metal parts according to claim I characterized in that   they consist of an alloy whose properties tribolDgi-   They are likely to be improved by superficial melting treatment. 9. Metal parts according to claim 8 characterized in that they consist of an aluminum alloy. 10. Metal parts according to claim 1, characterized in that   the zones consist of an alloy of the base metal with an element   or a feed compound such as said alloy has better   tribological properties as the base metal.   Metal parts according to claim 10, characterized in that   the feed compound belongs to the family of iron, nickel.   12. Process for obtaining metal parts according to claim 1, characterized in that a focused laser radiation of   merging areas of smaller width and depth. less than 150 pum.