Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Patent
1997-11-03
2000-03-07
Turner, Archene
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
51295, 51307, 51309, 2041921, 428336, 428697, 428698, 428699, C23C 1414
Patent
active
060337680
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to PVD hard coating materials for engineering components used in a hot environment, especially for tools for the coolant-free and lubricant-free machining of materials.
The coolant-free and lubricant-free machining of materials, in particular of metals like die steels or aluminium alloys, is increasingly gaining in significance, in particular in the automotive industry.
2. Description of the Prior Art
TiN and TiCN layers deposited by the known PVD and CVD methods cannot satisfy this object satisfactorily because both begin to oxidize at operating temperatures beyond 400.degree. C. and thus considerable wear arises, in particular at the cutting edges. This is because the oxides which are formed are very brittle and spall off from the TiN or TiCN coating due to their low bond strength and different thermal expansion. This leads to a continuous and considerable reduction of the layer thickness in the edge region during cutting operations at elevated temperatures. Analogous effects can also arise with forming tools.
It has been found that TiAlN applied by the PVD process as a hard material coating is much better suited to resisting the oxidation processes. It has been reported that the temperature at which oxidation sets in can be increased to 700 to 800.degree. C when the hard material layer consists, for example, of 50 at % Ti and of 50 at % Al.(W.-D. Munz, J. Vac. Sci. Technol., A4 (6) (1986) 2117).
Even higher Al contents have been reported, i.e. Al contents of up to 70 at % of the respective metal content. It is known from the field of turbine blade coating that the addition of yttrium increases the oxidation resistance of superalloys such as CoCrAlY or of thermally insulating layers of zirconium oxide.
In the hard material coating field a layer of TiYN has admittedly been reported with a Y-content of more than 10 at %; however, this layer proved to be unsuitable for industrial use, mainly because of its brittleness. (J. R. Roos, J. P. Celis, E. Vancoille, H. Veltrop, S. Boelens, F. Jungblut, J. Ebberink, H. Homberg, Thin Solid Films, 193/194 (1990) 1542).
SUMMARY OF THE INVENTION
An object of the invention is to thermally stabilize the interface between the hard material coating and the respective substrate and to further reduce the onset of oxidation.
For this purpose, the invention proposes the addition of small quantities of yttrium to binary, ternary or quaternary TiAl-based multi-component layers. Preferably the yttrium is unevenly distributed with respect to the growth direction of the coating. That means that the distribution is not uniform perpendicular to the substrate surface.
In particular, pure yttrium or alloys containing yttrium and scandium, are added to todays well known TiAlN.
In accordance with the invention, yttrium is preferably added in the concentration range between 0.1 to 4.0 at % in ternary TiAlN alloys or in TiAlN/CrN, TiAlN/ZrN, TiAlN/TiN, TiAlN/MoN and TiAlN/WN multi-layer coatings. It will be understood that the percentage value of yttrium is quoted as a percentage of the metallic constituents only. Preferably a Y-content of only 1.5 to 2.0 at % of the Ti and Al constituents is recommended and used.
The coating of the tools is preferably produced by sputtering (unbalanced magnetron UBM) (W.-D. Munz, Surf. Coat. Technol., 48(1991) 81), cathodic arc evaporation (e.g. steered arc) or with combination methods as cathodic arc evaporation/sputtering (W.-D. Munz, D. Schulze, F. J. M. Hauzer, Surf. Coat.Technol., 50 (1992) 169) or sputtering/low voltage electron beam evaporation (anodic arc evaporation) or combined low voltage evaporation/cathodic arc evaporation.
The uneven or non-uniform distribution of yttrium in the growth direction of the hard coating is achieved by the special choice of the deposition conditions. It has to be stated that the lateral distribution of the yttrium parallel to the substrate surface has to be as uniform as possible. The uneven distribution in growth direction is obtained
REFERENCES:
patent: 4252862 (1981-02-01), Nishida
patent: 4761346 (1988-08-01), Naik
patent: 4871434 (1989-10-01), Munz et al.
patent: 5208102 (1993-05-01), Schulz et al.
patent: 5306407 (1994-04-01), Hauzer et al.
patent: 5330853 (1994-07-01), Hofman et al.
patent: 5549975 (1996-08-01), Schulz et al.
Brooks John Stuart
Donohue Lee Adrian
Muenz Wolf-Dieter
Smith Ian
Hauzer Industries BV
Turner Archene
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