Abstract: The present invention relates to a coated cemented carbide insert with a binder phase enriched surface zone. The WC-grains have an average grain size in the range 1.0-3.5 &mgr;m, preferably 1.3-3.0 &mgr;m and the number of WC-grains larger than 2 times the average grain size is less than 10 grains/cm2 measured on a representative polished section 0.5 cm2 large, preferably less than 5 grains/cm2, and the number larger than 3 times the average grain size is less than 5 grains/cm2, preferably less than 3 grains/cm2. The cemented carbide is made by powder metallurgical methods and is in particular characterized in that the cooling rate, CR, from the sintering temperature, ST, exhibits the relationship 10<CR·(ST-1300)/1000<17.

Abstract: Borehole opener, particularly for enlarging this hole underneath a casing in the field of oil prospecting, comprising a body (2) of longitudinal axis (3), a duct (4) for drilling fluid, formed longitudinally in the body (2), and at least two hole-opening arms (5) which have an active part (7) equipped with cutting means (8), which are distributed symmetrically in the body (2) about the longitudinal axis (3), and which are arranged therein in such a way that they can be moved between a position of rest (9) in the body (2) and an active position (10) partially out of the body (2); in this hole opener in order to move it from the position of rest (9) to the active position (10), each arm (5) has a face (12), internal to the body (2), designed to be subjected directly, in the same way as an active face of a piston, to the pressure of the drilling fluid flowing through the body (2).

Abstract: There is disclosed a method of sintering cemented carbide bodies including heating said bodies to the sintering temperature in a suitable atmosphere and cooling. If said cooling at least to below 1200° C. is performed in a hydrogen atmosphere of pressure 0.4-0.9 bar cemented carbide bodies with no surface layer of binder phase are obtained. This is an advantage when said bodies are to be coated with wear resistant layers by the use of CVD-, MTCVD- or PVD-technique.

Abstract: A coated cemented carbide cutting tool (indexable inserts) for the wet or dry milling, particularly at high cutting speeds, of stainless steels of different composition and microstructure, but also for the milling of non-stainless steels such as low carbon steels and low and medium alloyed steels is disclosed. The coated WC−Co based cemented carbide insert includes a specific composition range of WC+Co without any addition of cubic carbides by a low W-alloyed Co binder and by a narrow range defined average WC grainsize, and a hard and wear resistant coating including a multilayered structure of sublayers of the composition (TixAl1−x)N with repeated variation of the Ti/Al ratio.