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
  • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
  • C23C30/005—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process on hard metal substrates

Definitions

• This invention relates to coated articles comprising hard metals, refractories, and especially cemented carbide substrates. More particularly, it relates to such coated hard metal or coated cemented carbide products which are adapted to receive an aluminum oxide or other oxide wear layer which is very firmly bonded to the substrate.
• Such hard metal and/or cemented carbide substrates are used in tools for machining and cutting metals. Their already high wear resistance can be significantly improved by providing oxide wear layers, such as aluminum oxide wear layers, as described in U.S. 3,736,107 and 3,836,392.. However, it has become apparent that proper steps must be taken to adequately bond the oxide layer to the hard metal or cemented carbide substrate if the superior wear resistance of the oxide layer is to be realized.
• a novel coating procedure has now been discovered which provides aluminum oxide and other oxides (e.g., hafnium oxide, zirconium oxide and the like) bonded to the substrates with adherence equal to that obtained in the said '631 patent, which can be performed at normal coating temperatures.
• Such a procedure in its broadest aspects comprises providing a thin surface-oxidized bonding layer comprising an oxide, a carbide or oxycarbide of at least one of tantalum, niobium and vanadium, optionally aluminiz- ing the bonding layer, and finally providing an outer oxide wear layer.
• the present bonding layer is thin, not useful as a barrier, and possesses a composition novel in its chemical constituents. All of the foregoing patents and publications are incorporated herein by reference.
• an article of manufacture comprising:
• the substrate is a cobalt cemented carbide; the bonding layer is 0.1 to 0.5 microns thick; aluminum is added to the bonding layer by a process to be described layer; the oxide wear layer is aluminum oxide; and the wear layer is 0.5 to 20 microns thick.
• a hard metal or cemented carbide substrate is pretreated for the reception of a wear resistant oxide coating by treating the substrate in a first atmosphere selected from carbide and oxycarbide forming atmospheres to form a bonding layer of metal selected from at least one of tantalum, niobium or vanadium on said substrate and heating the coated substrate in a second oxidizing atmosphere until at least about 50% of the surface is oxidized.
• an oxide outer wear layer preferably an aluminum oxide wear layer
• the bonding layer may bond or form the oxide wear layer directly to the substrate or to other layers with which the substrate is previously coated:
• One preferred previously coated layer is TiC although broadly, this layer may comprise a carbide, nitride or carbonitride of Ti, Zr, Hf, V, Cr, W, Si, B which is an intermediate layer.
• One convenient way of proceeding is to provide a coating furnace held at a temperature of from about 800° C to 1300°C., and to expose a substrate in the furnace to the following sequential steps:
• a commercial cemented carbide cutting tool insert of composition 85.5% WC, 6% TaC, 2.5% TiC and 6% Co was coated in the following manner:
• the coated insert was used to machine cast iron at 400 sfpm, .010 in./rev. feed rate, and the wear resistance was compared with that obtained using a commercial insert which requires a high temperature diffusion operation to make the coating.
• a cemented carbide insert having the same composition as Example 1 above was coated with A1 2 0 3 in the following manner:
• the resultant coated insert had a 3-micron Al 2 0 3 coating firmly bonded to the cemented carbide substrate, through a bonding layer about 0.2 microns thick.
• a cemented carbide insert having the same composition as Example 1 above was pretreated then coated with Al 2 0 3 in the following manner at a furnace temperature of 1050°C, and l atmosphere pressure.
• the resultant coated insert had a 3-4 microns Al 2 0 3 coating firmly bonded to the cemented carbide substrate, through a bonding layer about 0.2 microns thick.
• a coated insert according to this invention was obtained.
• a commercial cemented carbide cutting tool insert comprising 85.5% WC; 6%-TaC 2.5% TiC and 60% Co and coated with TiC of five microns thickness is subjected to the following sequence of steps in a furnace at temperature of 1050°C. and 1 atmosphere pressure:
• Example 2 Iron was incorporated into the surface of a TiC coated cemented carbide cutting tool insert by rubbing its cutting surfaces with a piece of soft iron.
• the general procedure of Example 1 was then used to deposit a very thin coating of niobium carbide by the exposure of the treated surface to a mixture of H 2 and CbCl 5 gases for about 10 minutes at 1050°C.
• the resultant CbC coating was allowed to diffuse with the Fe (and TiC) for about 20 minutes and then this surface was lightly oxidized by exposure to a mixture of H 2 - 5% C0 2 at 1050°C. for about 15 minutes.
• A1 2 0 3 - coated a very strong bond was obtained between the A1 2 0 3 coating and the TiC-coated surface, noticeably better than the adhesion obtained using the same process without the Fe treatment.
• tantalum or niobium chloride in the steps of the. above examples is critically specific for the achievement of the desired high level of coating adherence in a single furnace operation. While titanium chloride may be used in these steps in addition to tantalum or niobium chloride, the adherence is not as good if only titanium chloride is used. Since vanadium belongs to the same group as tantalum and niobium (Group . VB), its effectiveness is probable.
• the bonding layer may be treated with Al, Fe, Co, Ni, to improve the bond with the A 1 2 0 3 outer layer.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Vapour Deposition (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

Priority Applications (1)

Applications Claiming Priority (4)

Publications (2)

Family

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Family Applications (1)

Country Status (3)

Cited By (7)

Citations (4)

• 1982
  • 1982-12-06 EP EP19820306473 patent/EP0083842B1/de not_active Expired
  • 1982-12-06 DE DE8282306473T patent/DE3279814D1/de not_active Expired
  • 1982-12-16 CA CA000417957A patent/CA1198945A/en not_active Expired

Patent Citations (4)

Non-Patent Citations (2)

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