(19)
(11) EP 0 822 265 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
15.04.1998 Bulletin 1998/16

(43) Date of publication A2:
04.02.1998 Bulletin 1998/06

(21) Application number: 97115279.8

(22) Date of filing: 18.05.1995
(51) International Patent Classification (IPC)6: C22C 29/02, C22C 29/08, C22C 29/04
(84) Designated Contracting States:
DE FR GB IT

(30) Priority: 19.05.1994 JP 105584/94
15.02.1995 JP 49290/95

(62) Application number of the earlier application in accordance with Art. 76 EPC:
95107670.2 / 0687744

(71) Applicant: SUMITOMO ELECTRIC INDUSTRIES, LTD.
Osaka-shi, Osaka (JP)

(72) Inventors:
  • Tsuda, Keiichi
    1-1, Koyakita 1-chome, Itami-shi, Hyogo (JP)
  • Isobe, Kazutaka
    1-1, Koyakita 1-chome, Itami-shi, Hyogo (JP)
  • Ikegaya, Akihiko
    1-1, Koyakita 1-chome, Itami-shi, Hyogo (JP)
  • Kitagawa, Nobuyuki
    1-1, Koyakita 1-chome, Itami-shi, Hyogo (JP)

(74) Representative: Herrmann-Trentepohl, Werner, Dipl.-Ing. 
Patentanwälte Herrmann-Trentepohl Grosse - Bockhorni & Partner Forstenrieder Allee 59
81476 München
81476 München (DE)

 
Remarks:
This application was filed on 03 - 09 - 1997 as a divisional application to the application mentioned under INID code 62.
 


(54) Nitrogen-containing sintered hard alloy


(57) A nitrogen-containing sintered hard alloy includes a hard phase containing WC serving as an essential element and a carbide, nitride or a carbo-nitride of at least one transition metal being selected from the groups 4,A 5A and 6A of the periodic table or a composite carbo-nitride thereof and a binder phase containing Ni, Co and unavoidable impurities, an exudation layer containing a metal binder phase, mainly composed of Ni and Co, and WC being present on an alloy of this part, wherein the exudation layer is internally divided into a three layers in order of an outermost layer and an intermediate layer and an lowermost layer, wherein the outermost layer containing at least 0 percent by volume and not more than 30 percent by volume of WC with a rest being formed by a metal binder phase, the intermediate layer contains at least 50 percent by volume and not more than 100 percent by volume of WC with a rest being formed by a metal binder phase, the lower layer containing at least 0 percent by volume and not more than 30 percent by volume of WC with a rest being formed by a metal binder phase, wherein the outermost and lowermost layers being at least 0.1 µm and not more than 10 µm in thickness, the intermediate layer being at least 0.5 µm and not more than 10 µm in thickness. According to this composition, it is possible to provide a nitrogen-containing sintered hard alloy which can be employed as a cutting tool having high reliability with no surface coating also in working under conditions bringing a strong thermal shock.






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