Titanium-based carbonitride alloy with nitrided surface zone

Details Titanium-based carbonitride alloy with nitrided surface zone Titanium-based carbonitride alloy with nitrided surface zone

1999-07-22

2001-02-27

Mai, Ngoclan (Department: 1742)

Specialized metallurgical processes, compositions for use therei

Compositions

Consolidated metal powder compositions

C075S242000, C051S307000, C407S119000

Reexamination Certificate

active

06193777

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a liquid phase sintered body of a carbonitride alloy with titanium as main component which has improved properties particularly when used as cutting tool material in cutting operations requiring sharp edges in combination with high wear resistance and plastic deformation resistance. This has been achieved by heat treating the material in a nitrogen atmosphere.
Titanium-based carbonitride alloys, so-called cermets, are today well established as insert material in the metal cutting industry and are especially used for finishing. They comprise carbonitride hard constituents embedded in a metallic binder phase. The hard constituent grains generally have a complex structure with a core surrounded by a rim of other composition.
In addition to titanium, group VIa elements, normally both molybdenum and tungsten and sometimes chromium, are added to facilitate wetting between binder and hard constituents and to strengthen the binder by means of solution hardening. Group IVa and/or Va elements, i.e., Zr, Hf, V, Nb and Ta, are also added in all commercial alloys available today. All these additional elements are usually added as carbides, nitrides and/or carbonitrides. The grain size of the hard constituents is usually <2 &mgr;m. The binder phase is normally a solid solution of mainly both cobalt and nickel. The amount of binder phase is generally 3-25 wt %. Other elements are sometimes added as well, e.g., aluminum, which are said to harden the binder phase and/or improve the wetting between hard constituents and binder phase.
One main advantage with cermets compared to WC-Co-based material is that relatively high wear resistance and chemical inertness can be obtained without applying surface coatings. This property is utilized mainly in extreme finishing operations requiring sharp edges and chemical inertness to cut at low feed and high speed. However, these desirable properties are generally obtained at the expense of toughness and edge security as well as ease of production. The most successful materials have a large nitrogen content (N/(C+N) often exceeding 50%) which makes sintering in conventional processes difficult due to porosity caused by denitrification. The high nitrogen content also makes the material difficult to grind. Grinding may be necessary to obtain sharp defect free edges and close tolerances. Ideally, for extreme finishing operations, one would like to have an uncoated cermet with low to moderate nitrogen content for ease of production, but with a wear resistance essentially the same as PVD- or CVD-coated material.
U.S. Pat. No. 4,447,263 discloses inserts of a titanium-based carbonitride alloy provided with a wear resistant surface layer of carbonitride or oxycarbonitride alone or in combination where the surface layer is completely free from binder phase. The layer is obtained by a heat treatment at 1100-1350° C. in an atmosphere of N
2
, CO and/or CO
2
at subpressure.
Another example is in U.S. Pat. 5,336,292 where the surface layer contains a low amount of binder phase but is separated from the interior of the material by a sharp interface to a binder phase enriched zone. The layer is obtained by heat treatment in an atmosphere of N
2
and/or NH
3
possibly in combination with at least one of CH
4
, CO and CO
2
at 1100-1350° C. for 1-25 hours at atmospheric pressure or higher.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of this invention to avoid or alleviate the problems of the prior art.
It is further an object of the present invention to provide a sintered titanium-based carbonitride alloy, which has been heat treated to obtain a 5-60 &mgr;m thick surface zone with high nitrogen content. The heat treatment is performed as a process step included in the cooling part of the sintering cycle or as a separate process, e.g., as last production step, after any optional grinding operation has been performed.
In one aspect of the invention, there is provided a cutting tool insert of sintered titanium-based carbonitride alloy containing hard constituents based on Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and/or W in a cobalt binder phase wherein said alloy has a 5-60 &mgr;m thick nitrogen enriched surface zone and a Co content at the surface in the range 50-150% of the nominal Co value in the insert as a whole.
In another aspect of the invention, there is provided a method of manufacturing a sintered body of titanium-based carbonitride alloy, containing hard constituents based on Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and/or W in a cobalt binder phase comprising liquid phase sintering followed by a nitriding process said nitriding being performed at a temperature of 1150-1250° C. in an atmosphere comprising 500-1500 mbar nitrogen gas for 1-40 hours.


REFERENCES:
patent: 4276096 (1981-06-01), Kolaska et al.
patent: 4447263 (1984-05-01), Sugizawa et al.
patent: 4985070 (1991-01-01), Kitamura et al.
patent: 5110543 (1992-05-01), Odani et al.
patent: 5336292 (1994-08-01), Weinl et al.
patent: 5577424 (1996-11-01), Isobe et al.
patent: 5694639 (1997-12-01), Oskarsson et al.
patent: 95/30030 (1995-11-01), None

Affiliated with

Also associated with

Rating

Titanium-based carbonitride alloy with nitrided surface zone does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Titanium-based carbonitride alloy with nitrided surface zone, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Titanium-based carbonitride alloy with nitrided surface zone will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2573419