Cutters – for shaping – Comprising tool of specific chemical composition
Patent
1998-05-01
2000-06-27
Pitts, Andrea L.
Cutters, for shaping
Comprising tool of specific chemical composition
407120, 407118, 428698, B23B 2714
Patent
active
060799137
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a cutting tool, especially for chip-removal machining, comprised of a hard-metal substrate body, ceramic substrate body, or cermet substrate body, which is coated with a surface coating. The invention also relates to a process for coating this cutting tool as well as to the use of this cutting tool.
BACKGROUND OF THE INVENTION
Aside from uncoated cutting tools of hard metals, cermets or ceramics, coated cutting inserts have developed into considerable significance in metal machining. It is known, for example, to provide shaped bodies which are comprised of at least the carbide of tungsten, titanium, niobium and tantalum, as well as metallic cobalt, as the binder, whereupon one or more surface layers can be applied by CVD, PVD or plasma CVD processes. These can be comprised of hard carbides, nitrides or carbonitrides of the elements titanium, zirconium or hafnium, or also of aluminum oxide.
It is especially known also to provide multilayer coatings of the layer sequence TiC, Ti(C,N), and TiN, optionally with an outer Al.sub.2 O.sub.3 layer. With such coated cutting tools, high machining rates and long working lives can be achieved when in turning, milling or boring of the workpiece a lubricating liquid is supplied for corresponding cooling. The cooling lubricant liquid uses mainly an aqueous emulsion whose main component, namely water to 95% effects the requisite cooling of the cutting edge. The emulsified or solubilized additives are necessary to supply the requisite lubrication during the machining process, for resisting corrosion and to protect the workpiece against chemical attack. It is a drawback of the mentioned additives that they are environmentally unfriendly. Indeed it has been found that toxic additives like chloroparaffins or benzotriazol should be replaced by less environmentally hazardous substances and simultaneously that the recycling or disposal of the cooling lubricant, are associated with not insignificant costs which may not be overcome as a consequence of the increased machining efficiency and the higher useful lives of the tools.
From an economical viewpoint it is advantageous to operate without a cooling lubricant in a dry mode and to be satisfied with a higher tool wear. This latter approach is largely practiced for example with short-chip workpieces like those of cast steel. With long-chip steels, the removed chip contacts the cutting tool over a large region and because of the increased contact area at the cutting wedge of the cutting tool, increased heat development arises from friction. A solution known in the art is to provide low-friction coatings of the cutting tool, for example of aluminum oxide, to minimize the cutting tool wear. This approach does not provide general satisfaction when the operation uses a cooling lubricant.
In EP 0 634 905 B1 it is proposed to provide workpieces with "soft" layers of a chalcogenide compound like molybdenum disulfide or molybdenum diselenide. Such layers can only be produced by means of a costly PVD process and increase, because of reduced abrasion resistance, the useful life of the cutting tool in the case of steel machining only marginally.
OBJECT OF THE INVENTION
It is an object of the present invention to provide a surface-coated cutting tool which, even without a cooling lubricant, supplies a satisfactory machining rate and life.
SUMMARY OF THE INVENTION
Surprisingly it has been found that thin surface coating of both hexagonal and amorphous boron nitride can significantly improve life of cutting inserts in dry cutting.
Boron nitride can be available in several modifications. One of these modifications is cubic boron nitride (CBN) or polycrystalline cubic boron nitride (PCB). CBN has a crystal structure which has a very high hardness (Vickers hardness of 4000 to 6000). This cubic modification corresponds to that known from diamonds and results when boron nitride is pressed under high temperatures (1500 to 1700.degree. C. and high pressure (5.times.10.sup.10 Pa (like that for pro
REFERENCES:
patent: 4853196 (1989-08-01), Koshida et al.
patent: 5053365 (1991-10-01), Shore et al.
patent: 5223337 (1993-06-01), Van Den Berg et al.
patent: 5286533 (1994-02-01), Komatsu et al.
patent: 5299892 (1994-04-01), Pickert
patent: 5364209 (1994-11-01), Santhanam et al.
patent: 5624766 (1997-04-01), Moriguchi et al.
"Wenn das Umfeld stimmt . . . " by Abel, published in Industrie-Anzeiger 86/1990.
"Eigenschaften und Anwendungen von Cermet-Schneidplatten" by Urano et al., published in Werkstatt 7 Betrieb 118/1985/9.
"Beschichtete Umformwerkzeuge . . . " by K. Keller et al. published in Bander Bleche Rohre Jul. 1991.
"CVD-Beschichtung bei Mitteltemperaturen" by Mathesius et al., published in Industrie-Anzeiger No. 31 of 17.4 1985/107.
"Hartstoffbeschichten von Werkzeugen" by K. Herden, published in Technische Rundschau No.36-1993.
"Polykritsalline Diamant--und Bornitrid-Werkzeuge" by Schwaighofer et al., published in Prazisions-Fertigungstechnik Sep. 1985.
"Boron nitride coating of cutting tools" by Morita et al., Chemical Abstracts 117 (1992) No. 2, Columbus, OH, US.
"Mit passenden Schneidstoffen innovativ fertigen" (VDI-Z 132 (1990) No. 3, Mar. 1987.
"Infrared spectroscopic investigantion on h-BN and mixed h/c-BN thin films" by Jager et al. (2194 Thin Solid Films 245(1994) Jun. 1, Nos. 1/2 Lausanne, CH.
Konig Udo
Tabersky Ralf
Westphal Hartmut
Dubno Herbert
Pitts Andrea L.
Tsai Henry W. H.
Widia GmbH
LandOfFree
Cutting tool, process for coating a cutting tool and use thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cutting tool, process for coating a cutting tool and use thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cutting tool, process for coating a cutting tool and use thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1778958