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
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
  • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
  • C23C8/24—Nitriding
  • C23C8/26—Nitriding of ferrous surfaces
• • 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
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/80—After-treatment

Definitions

• the present invention relates to a treatment method for simultaneously improving the corrosion resistance and friction properties of ferrous metal parts.
• ferrous metal parts can be imparted by nitriding then oxidation, good friction properties and good corrosion resistance.
• nitriding ferrous metal parts in particular nitriding by baths of molten cyanates and carbonates as described in FR-A-2 171 993 and FR-A-2 271 307, or else nitriding by ionized nitrogen atmosphere, which improve the friction properties of these parts, reducing the coefficient of friction, and increasing resistance to wear and seizure.
• the present invention is also based on the observation that many parts are cleaned in the usual way, in particular before they are assembled, when it is well known that they do not justify such cleaning and for which it is therefore not necessary to carry out a surface treatment resistant to conventional cleaning products.
• the present invention provides a method of treating ferrous metal parts to simultaneously improve their corrosion resistance and their friction properties, method in which the parts are nitrided, oxidized and receive a final coating, characterized in that the nitriding followed by oxidation leads to the formation of a layer consisting of a compact deep sublayer and a porous surface sublayer, said surface sublayer having a thickness of between 5 and 25 "m and having through porosities of diameter between 0.2 and 3 "m, and in that the nitrided and then oxidized parts are impregnated with a hydrophobic wax, said wax being a carbonaceous organic compound with high molecular weight of between 500 and 10,000 , surface tension in the liquid state between 10 and 73 mN / m, the contact angle between the solid phase of the surface layer and the wax in the liquid state being between 0 and 75 degrees.
• the surface sublayer contains more than 60% of solid phase Fe2 ⁇ 3N, has a hardness between 550 and 650 HV 0.1 and a roughness between 0.3 and 1.5 ”CLA
• the impregnation wax is chosen from the list: natural waxes, or synthetic polyethylene, polypropylene, polyesters, fluorinated waxes or modified petroleum residues.
• the method according to the invention has the advantages of being inexpensive and easy to implement even for industrial productions on series parts, of conferring on the treated parts high technical performance even when these are of complex shapes.
• the composition of the nitrided layer, its thickness and its hardness are adjusted so that it resists wear, without however being fragile, because then it would flake under the effect of shocks.
• the compact hexagonal structure of the Fe2 ⁇ 3N phase of the iron / nitrogen equilibrium digram offers good deformation capacity, thanks to a high atomic density on the sliding plane and is thus particularly favorable to friction applications.
• the nitriding is carried out in a bath of molten salts according to FR-A-2 171 993, consisting essentially of carbonates and cyanates of alkali metals K, Na and Li, the anion CO32 ⁇ being present for 1 to 35% by weight and the CNO ⁇ anion for 35 to 65% by weight, while, in the total weight of the alkali cations, the weight proportions are 25-42.6% for Na+, 42, 6-62.5% for K+ and 11.3-17.1% for Li+.
• the nitriding salt bath further comprises a sulfur species in an amount such that the weight content of elemental sulfur is between 0.001 and 1%, according to FR-A-2 271 307.
• the oxidation treatment makes it possible, in addition to already improving the corrosion resistance in itself, but also when it is correctly conducted, to adjust the surface properties of the solid phase, so as to lead to maximum effectiveness of the impregnation of the wax.
• the inventors have good reason to believe that the presence in the combination layer of a strongly electron donor or acceptor element capable of locally creating electric dipoles is highly rewarding; in this case, chemical bonding forces are created which locally reinforce the capillary forces. To this end, preference will be given to the presence of sulfur as well as oxygen in the surface sublayer.
• the oxidation will be carried out in a bath of molten salts according to FR-A-2 525 637, generally at temperatures between 350 ° and 450 ° C.
• Test specimens were used, formed by pairs comprising a ring with a diameter of 35 mm and a plate with dimensions of 30 ⁇ 18 ⁇ 8 mm, made of XC 38 steel.
• the sulfonitrided layer comprises, in composition by weight, approximately 87% of iron nitride ⁇ (Fe2 ⁇ 3N), approximately 10% of nitride ⁇ '(Fe4N), the remainder being iron oxides, sulphides and oxysulphides. Its hardness is 600 HV 0.1.
• the sulfonitrided layer has a thickness of 15 "m with a compact deep underlay of 8" m thick and a porous surface underlay of 7 "m, the pore diameter being between 1 and 2.5" m, with a maximum pore density in the range 1.5 - 2 ”m.
• the parts are immersed for 20 min in a salt bath according to FR-A-2 525 637, at a temperature of 420 ⁇ 15 ° C.
• the nitrided layer of the parts comprises nitride ⁇ with 6% of nitride ⁇ ', while all the oxysulfurized compounds have been transformed into iron oxide magnetite (Fe3O4), with oxygen inserted into the 2 to First 3 surface micrometers.
• Fe3O4 iron oxide magnetite
• the surface roughness is then 0.6 "CLA.
• the corrosion resistance in standard salt spray is established at 50-60 hours for the nitrided parts, and 200-250 hours for the nitrided then oxidized parts, while the parts before treatment exhibit generalized corrosion after only a few hours.
• the parts thus nitrided and then oxidized are impregnated by immersing them for 2 min in polyethylene wax melted at the temperature of 150 ° C. On leaving the melted wax bath, the pieces are wiped with a clean, dry cloth.
• the surface tension of the viscous phase is 32 mN / m and the contact angle between solid phase, here the sulfonitrided then oxidized layer and viscous phase is 41 degrees.
• the corrosion resistance then exceeds 2,000 hours, while the friction test can continue for 50 minutes, for a cumulative wear of only 25 »m and a coefficient of friction of 0.18.
• thermochemical nitrocarburization treatment in a nitrided-carbon medium, for example in a salt bath or alternatively by gaseous route, subject however to limiting the embrittling effect of carbon, which in practice limits its rate to 3%. the surface diffusion layer.
• thermochemical treatment it was also possible to verify that the oxidation subsequent to the thermochemical treatment can be carried out, in addition to a salt bath, by a simple or ionized gas route.
• the final coating can be carried out by immersing the parts, no longer in a bath of molten wax, but in a solvent containing the said wax in the dissolved state.
• Car locksmith parts of complex shape made of stamped sheet metal, punched, folded, were nitrided, according to the conditions taught by FR-A-2 171 993 and FR-A-2 171 993 and FR-A-2 271 307.
• Au leaving the nitriding treatment the parts have undergone an oxidation treatment under the conditions taught by FR-A-2 525 637.
• an impregnation treatment was carried out with a wax of the type derived from sulphonate modified petroleum, by immersing the pieces in said wax dissolved at a rate of 70 g / liter in white spirit.
• the parts meet all the specifications required by car manufacturers and in particular a resistance to corrosion in salt spray for at least 200 hours without “white rust” and at least 400 hours without “red rust", the parts which have undergone, before exposure to the salt spray, a duration of 1 hour at a temperature of 120 ° C.
• tail lifts such as freight elevators for trucks, or for steel forklifts 35 CD 4.
• the method according to the invention was applied to playing balls, in particular for courttanque and Provençal games. These balls are formed by two hemispherical caps in alloy steel type 25 CD 4, welded along a diametrical plane. After calibration adjustment, they are heat treated to present in the mass a specified hardness, greater than or equal to 110 daN / mm2. Finally, they undergo the same surface conditioning as in the four previous examples.
• the balls have a set of characteristics, coefficients of friction and regularity of surface which, in the opinion of specialists, are particularly appreciated by high level players, participating in tournaments and official competitions and in particular: very good resistance to corrosion, very low wear rate guaranteeing compliance with regulations which stipulate that the weight loss due to play must not exceed 15g below the marked weight, ability to withstand shocks without damage, pleasant aesthetics in bright black color .
• the final polish can be maintained by the player himself.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Treatment Of Metals (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=9415150

Family Applications (1)

Country Status (9)

Families Citing this family (20)

Family Cites Families (14)

• 1991
  • 1991-07-16 FR FR9108946A patent/FR2679258B1/fr not_active Expired - Lifetime
• 1992
  • 1992-06-10 TW TW081104531A patent/TW223663B/zh active
  • 1992-06-11 US US07/896,928 patent/US5346560A/en not_active Expired - Lifetime
  • 1992-06-12 EP EP92401633A patent/EP0524037B1/fr not_active Expired - Lifetime
  • 1992-06-12 ES ES92401633T patent/ES2071455T3/es not_active Expired - Lifetime
  • 1992-06-12 DE DE69202114T patent/DE69202114T2/de not_active Expired - Fee Related
  • 1992-07-11 KR KR1019920012368A patent/KR100213670B1/ko not_active Expired - Fee Related
  • 1992-07-13 BR BR929202658A patent/BR9202658A/pt not_active IP Right Cessation
  • 1992-07-15 JP JP4188032A patent/JP2502243B2/ja not_active Expired - Lifetime

Also Published As

Similar Documents

Legal Events