FR2541154A1 - COMPOSITE BODY, IN PARTICULAR A HELICAL BIT, CONSISTING OF A SUBSTRATE COATED WITH A HARD SURFACE LAYER RESISTANT TO WEAR - Google Patents

Abstract

COMPOSITE BODY CONSTITUTED BY A SUBSTRATE COATED WITH A HARD SURFACE LAYER RESISTANT TO WEAR. FOR CUTTING TOOLS OR WEAR PARTS COATED WITH A THIN METAL NITRIDE SURFACE LAYER, IT IS POSSIBLE TO OBTAIN A LONGER LIFETIME BY MAKING A LAYER IN THE FORM OF A DOUBLE LAYER, THE LAYER INTERIOR CONSISTING ESSENTIALLY OF SUBSTO-ECHIOMETRIC MEN (X BEING LESS THAN 0.9 AND PREFERREDLY GREATER THAN 0.5), AND THE OUTER LAYER CONSISTING ESSENTIALLY OF STO-ECHIOMETRIC MEN (X BEING GREATER THAN 0.9 AND PREFERREDLY NOT MORE THAN 0.5) EQUAL TO 1), ME REPRESENTING A METAL THAT BELONGS TO GROUPS III TO VI OF THE PERIODIC CLASSIFICATION OF ELEMENTS.

Description

1. The invention relates to shaped bodies,

  for example, cutting tools or wearing parts,

  in thin and extremely wear-resistant surface layers It is known that the service life of different kinds of bodies, for example sintered carbide, ceramic, steel or other material cutting inserts, can be considerably lengthened by the application of layers

  hard surfaces The coating of such bodies by

  refractories, to increase their resistance to usu-

  These layers are usually made of carbides, nitrides and / or metal oxides, which have been used extensively for a long time.

  groups III-VI of the periodic table of

  mentset ellesse characterize by a very great hardness

and good chemical stability.

  Of the coating materials mentioned above,

  metal nitrides belonging to groups III-VI of the Periodic Table, in particular the

  titanium nitride (Ti N), have revealed properties that are particularly

  particularly favorable in combination with other

  coating materials, eg titanium carbide

  (Ti C) and alumina (A 12 03) However, a single layer

  However, nitride only allows limited applications because of its unsatisfactory wear resistance and insufficient substrate adhesion. In accordance with the present invention, it has been established that it is possible, however, to obtain

  improved even when using Ni-based layers.

  as a coating material The layer according to the

  must then include at least two separate layers.

  nitride, the inner layer being Mee Nx

  substoichiometric, where x is less than 0.9 and preferably

  more than 0.5, and the outer layer

  in both stoichiometric and nearly stoichiometric M n, where x is greater than 0, 9 and preferably between 0.9 and 1, O Me represents a metal belonging to groups 2.

  III-VI of the periodic classification of the elements

  total thickness of the nitride layer is generally 1-

  pm, the inner layer generally having a thick

  the outer layer having a thickness of

  usually 1-2 pm. The invention has proved to be particularly

  useful in the coating of substrates by means of

  Although what is known as "PVD" (depotven vapor phase), what follows will be described in detail the use of the invention in the coating of certain cutting tools, for example helico Xdaux drill / titanium nitride (Ti N), through the implementation of

  of this deposit technique.

  Wear-resistant coatings consisting of nitride, carbide and hard oxide with grades

  stoichiometric amounts of nitrogen, carbon and oxygen are de-

  I have known in themselves, for example by the Swedish patent 375 474 which describes carbide coatings, in particular titanium carbide (Ti C), having a substoechiometric carbon content, and by the French patent application 80 13 030 (European patent application published under number

  004378) which discloses Ti N and Ti NX coatings, x va-

  between 0, 4 and 1, 0 In these known techniques, the coating layers are not particularized as

  they are so in the present invention.

  The drill we are referring to is a drill of the type

  carbides (that is, it is equi-

  sintered carbide cutting inserts) and, thanks to

  the present invention, he has shown himself to be excellently

  properties, for example a high speed of penetration

  which allows for excellent diameter tolerances

  pierced, a perfect surface finish, good guidance of

  skins and excellent resistance of the cutting edges, this

  which leads to high productivity for drilling

  preferably alloyed or low carbon.

  This kind of forest is already known; it is a carbide tipped drill with two edges

  helical cutters starting from the center of rotation of the

3-

  ret and extending symmetrically with respect to the

  on both sides of the axis of the forest.

  pe are bent outwards in the direction of the

  rotation of the drill and they have a larger curvature

  from the center to the outer peripheral part of the forest. When using an uncoated drill that has this known geometry, we usually get a speed

  relatively large penetration, diameter tolerances

  relatively good surface finish and finish, and

  moderate shavings Due to the geometric design

  forest and the fact that a forest is always

  days a cutting speed variation that tends to zero in the center of the drill, it is generally created, however, an edge attached to a portion of the cutting edge If the reported edge is welded to the cutting edge and then , detaches, there is a risk of damage to the cutting edge which leads to an increased frequency of defects The formation of this reported edge is particularly troublesome in the area

  of the cutting edge in which its heavily

  gap is connected to a less curved part on the part

  curvature of the cutting edge, the chips are not

  place not only from the cutting edge perpendicular

  culturally to this one, but also along this

  edge in the peripheral direction of the forest In the

  less bent of the cutting edge, the direction of movement of the chips is essentially perpendicular

  at the cutting edge This gives rise to a certain

  chip pressure in the transition zone

  be two directions of chips, which in turn gives rise to increased constraints in operation in

  this area of the cutting edge When performing a drilling

  with an uncoated forest, deterioration is often observed.

  rations in the form of bites or chips, in particular

  bind in this area of the cutting edge These deteriorations

  usually cause a significant decrease in

  life of this kind of forest It has been found that these

  4. tériorations can be almost completely eliminated by applying to the drill a coating consisting of a layer

  titanium nitride (Ti N) in accordance with the present invention.

  This layer prevents the chips from binding to the

  cutting edge, especially in the critical area mentioned above.

born above.

  It is known that layers of nitride coating

  wear-resistant titanium (Ti N) can be prepared

  methods such as the chemical deposition method

  as vapor phase (CVD) or as the method (PVD) above.

  The first method normally requires a temperature of

  latively high substrate, usually 700-1000 O C,

  whereas the second method does not require a temperature

  As a result, this second method is particularly suitable for coating drills and similar articles, in which the support is made of steel

  It has been found that, by applying a coating c-ons-

  tituated by a layer of Ti N, according to the invention, by

  the so-called PVD technique, the thickness of the layer generally being

  At a level of 1 μm, and preferably of 5 μm, surprisingly good properties can be obtained with respect to edge protection and resistance.

  These properties are the result of excellent

  the adhesion of the coating layer to the substrate and the particular composition of the layer as to its content of titanium and nitrogen The Ti N layer consists of two layers of Ti N, the inner layer adhering to the substrate having generally a thickness of 46 feet and

  consisting of substoichiometric Ti NX, x generally

  0.5 to 0.9, and preferably 0.6 to 0.8. This inner layer has a pale yellow color which is characteristic of low nitrogen Ti Nx. If x is less than 0.5 phase, more precisely

  Ti 2 N, is formed but this phase is not suitable as

  The outer layer usually has a thickness of 1 to 2 μm and is formed by 5.

  Ti Nx, x being greater than 0, 9 and being normally

  taken between 0, 9 and 1, O The color of this outer layer

  is bright yellow, characteristic of Ti N stoichiometric

  than. The resulting protection of the cutting edge is

  obtained by eliminating the attached edge which is welded to the

  you as mentioned previously So,

  the cause of the deterioration of the forest is almost entirely

  removed and drills that are coated, depending on the

  the use of a Ti N-based coating

  reliability of production due to the very small decrease in their service life

  In the present invention, a pulverulent

  cathodic coating to coat the carbide tipped carbide drill The general principle of spraying

  conventional cathode, for example titanium> is well

  The titanium material, which is the target, is

  connected to a water-cooled cathode while the

  trat (ie the tool) constitutes the opposite anode

  at the cathode The gas that is used to maintain the effluent

  ve (PLASMA) between the cathode and the anode is generally argon at reduced pressure, of the order of 10 to 100 10 6

  bar, positive argon ions being accelerated towards the

  However, when depositing TiN according to the invention, it is possible to use another method called pulverization by means of a cathode voltage of 25 kV.

reactive magnetron.

  The principle of this alternative method is to

  apply in a dewatering system a magnetic field

  than annular penetrating perpendicular to the surface of the cathode It follows that the secondary electrons,

  who are ejected from the cathode, are captured in front of

  thode because of the Lorentz forces Thus, it creates an intensification of the plasma even stronger in front of the

  cathode This ionization-greatly increased results in a

  significantly higher deposition rate 6- The reactive cathode pulverization method is used when, for example, nitrides, carbides or titanium-type metal oxides have to be applied to a substrate When a titanium nitride coating is applied. , the gas used in the vacuum chamber is argon

or nitrogen -

  During the coating cycle, the substrates are mounted in a vertical position in a rectangular frame and

  are placed in a symmetrical position between two pairs of

  thodes equipped with titanium targets This arrangement of

  thode on both sides of the substrate support frame (pulveri-

  both sides) results in a uniform layer thickness over the entire cylindrical contour of the substrate,

example a helicoidal drill.

  The coating process essentially comprises two phases, namely a spray etching phase and a coating phase itself.

  spray attack, the substrate Pen-

  In this sputter etching phase, the substrate and the substrate support frame are subjected to a negative voltage of between 1000 and 1500 V, i.e.

  that the substrate itself and its support frame constitute

  at the same time kill the cathode and the target During this phase, an efflux occurs under an argon atmosphere at a

  pressure between 50 and 100 10-6 bar and with a

  2 to 4 A attack time (current in the substrate) The attack time should generally be between 5 and min.

  The actual coating phase is carried out

  at a pressure of 5 to 10 bar in a mixture of

  The optimum layers are obtained when using a gas containing 15 to 25% nitrogen. On each of the cathodes, a current of 70 to 80 A is applied.

  current for which an effusion is obtained between the catheter

  and other surfaces, with a voltage drop that varies between 300 and 500 V It is also possible to apply a negative voltage to the substrates (polarization 7. substrates), generally of the order of 100 to 500

  V, resulting in an acceleration of the argon ions posi-

  to the substrate and to the layer being formed.

  The so-called "bias sputtering" method in

  Anglo-Saxon structure (polarization spraying method)

  tion), has a positive effect in that the membership

  this between the layer and the substrate is improved and in that

  the microstructure of the layer is better suited for

  BACKGROUND OF THE INVENTION The coating speed of TiN, under the conditions mentioned above, varies between 0.05 and 0.20 pm / min.

  During the coating process, the temperature

  substrate (ie the tool in the application to the

  must not be less than 300-350 OC If the temperature

  is less than this value, the capacity of the adsorbed atoms to diffuse to the decreasing surface which increases

  the risk of obtaining porous layers.

  The examples below show the conditions in

  which, according to the invention, the wearing tools have been

  pe, as well as the results of cutting tests that were conducted with coated tools and uncoated tools

Example 1

  Two helical drills with

  14.4 mm diameter, were placed on the top row of a substrate support frame in a coating apparatus as mentioned above. The front portion of the drills, the cutting inserts and the tails were polished before the coating operation The drills were of the standard type

  The drills were heated at 5000 C for 10 minutes.

  The drills were drilled for 15 minutes at a substrate voltage of 1200 V and at a pressure of 58 x 10 ± 6 bar. The driving current varied between 1 and 3 A after the attack phase. , the targets were cleaned by

  spraying for 30 seconds, the openings being closed

  A coating of Ti N was applied under the following operating conditions. 8. Time :: 60 min. Bias voltage: 250 V Polarization current: 12 A Pressure: 18 x 10-6 bar Air flow: 1260 ml / min (normal conditions) Cathode current: 75 A The cathode voltage (cathode 1) varied between 392 and 398 V for a constant nitrogen flow rate of 545 ml / min,

  under normal conditions, during the first 27 months

  During the rest of the spraying phase (33 min), the cathode voltage (cathode 1) varied between 387 and 389 V for the same nitrogen flow rate.

Example 2

  The tools, coated with Ti N according to Example 1, were tested in drilling operations using the following operational parameters: Machine: Pedersen Vepematic Emulsion: Castrol Syntilo SW 3030 10% Material: Swedish standard 1672 Cutting characteristics (non-ferrous steel) combined with 0.45% of C) depth of cut: 40 mm / hole speed of rotation n = 1536 rpm linear cutting speed v = 70 m / min penetration speed: s' = 415 mm / min

Feed per revolution: S = 0.27 mm / rev.

  The drills were used on a total drilling depth of 28.2 m, after which the tests were stopped. One of the drills was also tested on another material (Swedish standard 1311, low-grade steel).

  carbon), this drill having drilled for an additional length

  23,5 m Thus, the total length of drilling for this

forest was 51, 7 m.

  A metallographic section of the surface layer

  This and the cutting edge showed that the total thickness was about 6 μm, the outer layer made of yellow Ti N having a thickness of 1.5 μm. The inner layer was more substoichiometric than with nitrogen as the outer layer

Example 3

  A large number of TiN coated drills (a few hundreds) of the invention were tested under the following conditions and compared with uncoated drills: Material: Swedish Standard 1672 (O-alloyed steel 45 % of C Linear cutting speed v = 70 m / min Rotational speed: N = 1114 rpm Penetration speed: s' = 334 mm / min Feed per revolution: S = 0, 30 mm / rev Drill diameter: O = 20 mm Result: Lifetime (mn) Maximum Average Without coating 10 20 With coating: 40 50 40 50

Example 4

  The same drilling tests were performed as in

example 3 to

  Material: Swedish standard Linear cutting speed Rotation speed Penetration speed Advance per revolution Drill diameter Result Uncoated With coating

Example 5

  2541 (reinforced steel, 280-320 HB): v = 55 m / min: N = 1167 rpm: s = = 292 mm / min: S = 0.25 mm / rev: O = 15 mm * Service life (mn) Maximum average

: 0, 5 20

: 30 35 3 35

  Drilling tests similar to those of Examples 3 and 4 to 10 were conducted. Material: Swedish Standard 131 Linear cutting speed Rotational speed Penetration speed Advance per revolution Drill diameter Result Uncoated With coating (low-grade steel) C

0, 13%)

  : v = 85 m / min: N = 1804 rpm: s' = 541 mm / min:: S = 0.3 mm / r 0 = 15 mm: _Lifespan (min) Maximum Average

: 5 -10 25 30

: 50 60 50 60.

  In Examples 35 the apparatus and emulsion were the same as in Example 2 In calculating the

  life expectancy, drills which have been shown to be de-

  for reasons other than damage

of their cutting edges 11.

Claims (1)

1 Composite body consisting of a substrate and a coating which comprises at least one layer of a wear-resistant metal nitride, said coating interesting at least part of the surface of the substrate, characterized in that the layer comprises a double coating with a thickness of I to 10 μm, the inner layer being in substoichiometric Me x, x being less than 0.9, and preferably greater than 0.5, the outer layer being constituted in Me N stoichiometric or almost stoichiometric, xx being greater than 0, 9 and preferably at most equal to 1, Me representing a metal belonging to groups III to VI of the periodic table of elements. Composite body according to claim 1, characterized in that the inner layer consists of Ti N x being between 0.5 and 0.9, and the outer layer consisting of Ti NX, x being greater than 0, 9 and preferably between 0, 9 and 1. 3 Composite body according to one of claims 1 and 2, characterized in that the thickness of the inner layer is from 4 to 6 μm and that the thickness of the outer layer is 1 to 2 μm. Composite body according to one of Claims 1 to 3, characterized in that the coating layer is deposited according to the so-called physical vapor phase (PVD) technique. Composite body according to one of Claims 1 to 3, characterized in that at 4, characterized in that the substrate is a helidrural drill, the cutting ply of which essentially consists of curved parts. Composite body according to one of the claims   1 to 5, characterized in that the substrate is a helical drill   coidus with sintered carbide   two helical cutting edges which start symmetrically   the axis of rotation of the drill and which are bent outwards in the direction of rotation of the drill, the   cutting edges with greater curvature at the center   only at the peripheral part of the forest.