Abstract: A semi-finished product is taken made of a metastable beta titanium alloy containing oxygen in the range 0.4% to 0.7% by weight, and nitrogen in the range 0.1% to 0.2% by weight (oxygen+nitrogen.ltoreq.0.8%). The product is subjected to solution treatment at a temperature in the range 800.degree. C. to 900.degree. C. It is then cooled very quickly (.gtoreq.200.degree. C. per hour), the part is machined, ageing treatment is applied at a temperature in the range 550.degree. C. to 650.degree. C. for in the range 10 minutes to 2 hours so as to transform half of the beta titanium into alpha prime titanium. The titanium alloy part contains 40% to 60% of beta alloy, the remainder being alpha prime alloy. The part has good mechanical properties, good breaking strength, and a good elastic limit.

Abstract: The present invention relates to a method and apparatus for surface treating and putting under compression prestress the inside wall of a cavity, in particular a cylindrical cavity of circular section. The apparatus comprises a bulb-shaped vibrator provided with a tubular portion designed to be engaged in an orifice of a cavity to be treated. It is associated with a vibration exciter designed to excite the vibrator at its resonant frequency. The treatment is obtained by shot in the form of balls being projected against the walls of the cavity and returned into the treatment field by a reflector. The method is particularly applicable to treating holes that are designed to receive the fixing pins of turbine blades.

Abstract: A surface coating (6) on martensitic steel for portions that rub by rotation is characterized in that it comprises a matrix (9) of NiMo in which grains of Cr.sub.3 C.sub.2 are embedded, 90% of which by weight are constituted by grains (8) in the range 10 .mu.m to 30 .mu.m. The coating has a low coefficient of friction and good adhesion.

Abstract: A method of nitriding a piece made of titanium alloy, in which a laser beam is directed onto the piece to obtain a small amount of surface melting in the impact zone of the laser, nitrogen under high pressure is blown immediately behind the impact zone of the laser beam so that the nitrogen penetrates into the impact zone once it has become semi-solid, and an inert gas is blown around the nitrogen so as to cover and overlap the laser impact zone. The apparatus of the invention includes a central tube for conveying the nitrogen and a circularly symmetrical duct around the axis of the central tube having inside and outside walls that are conical and that serve to convey the inert gas. The invention serves to obtain a hard surface layer having a thickness of 1 mm to 2 mm.

Abstract: An intermediate layer (3) constituted essentially by one or more of the following metals: Ni, Cu, Ti, and Al is interposed between the insert (2) and the part (1) to be clad, e.g. a vane for a steam turbine. After the part and insert assembly has been calibrated in an isothermal matrix, it is inserted in an isostatic pressing oven and raised to a temperature that is lower than the melting temperature of the layer (3) but higher than the forging temperature of the part. This method makes it possible to retain the metallurgical properties of the part.

Abstract: A method of manufacturing a protective insert (1) on a metal part (2) in which a foil (3) that serves as a barrier for gases is fixed between the part (2) and the insert (1), the edges of a metal capsule (4) are fixed to the edges of the foil (3), the space (5) between the capsule (4) and the part (2) is filled with a metal or ceramic powder and the ends of the capsule (4) are closed, the part (2) together with the filled capsule (4) are inserted in an isostatic pressing oven under a controlled atmosphere, with the pressure and the temperature being selected so that the powder is pressed in situ. The part (2) is cooled and then the capsule is removed before giving the part (2) together with its insert (1) the desired final shape. The method is very simple and it enables reliable products to be obtained.

Abstract: A method of laying a protective coating on a blade (1) made of a titanium alloy including vanadium. Vanadium powder is deposited on the portion of the blade (1) to be coated, the temperature of the powder is then raised to a temperature slightly greater than the melting point of vanadium. A powder of a cobalt-chromium-tungsten alloy is then deposited on the layer of vanadium, and this powder is raised to a temperature greater than its melting temperature and less than the melting temperature of vanadium. A blade made of an alloy of titanium including vanadium is characterized in that the blade includes a coating layer (5) of cobalt-chromium-tungsten alloy at its periphery, said layer being at least 1 mm thick and covering an underlayer of vanadium (6) which has a thickness lying in the range 0.5 mm to 1.5 mm. The resulting blade has very high resistance to abrasion by water droplets.

Abstract: The portion of the blade (1) to be coated has pure vanadium powder deposited thereon and the temperature of the powder is raised to a temperature which is slightly higher than the melting point of vanadium. Thereafter, a powder mixture is deposited on the vanadium layer, said powder comprising about one third by weight of titanium carbides, titanium nitrides, or titanium borides, which are bonded by a martensitic or austenomartensitic stainless steel. The powder is then raised to a temperature which is greater than its melting temperature and less than the melting temperature of vanadium. A titanium alloy blade it includes, on its periphery, a coating layer (5) which is at least 1 mm thick and which includes about one third by weight titanium carbides, or titanium nitrides, or titanium borides bonded by a martensitic or austenomartensitic stainless steel, said coating layer covering an under layer (6) of vanadium having a thickness lying between 0.5 mm and 1.5 mm.

Abstract: A protective tip (5) for a titanium steam-turbine blade (1), comprises 28% to 40% TiC, 12% to 26% Cr+Co, 1% to 6% Mo, 3% to 8% Ni 0.3% to 1.5% Cu and a balance of Fe. The tip (5) is brazed to the blade (1) by interposing a copper-based strip (6) having a thickness lying between 7/100 mm and 15/100 mm therebetween, then raising the temperature of the blade (1) and its tip (5) to between 900.degree. C. and 950.degree. C. in a vacuum or inert atmosphere oven. This temperature is maintained for a period of between thirty minutes and seventy-five minutes, and the oven is allowed to cool to ambient temperature. Optimal brazing also serves to harden the tip (5) possesses very good resistance to abrasion by water droplets.

Abstract: The present invention provides a steel containing, by mass:from 0.16% to 0.22% carbon (C)less than 0.3% silicon (Si)less than 0.5% manganese (Mn)from 0.6% to 0.9% nickel (Ni)from 10.7% to 12.3% chromium (Cr)from 0.8% to 1.1% molybdenum (Mo)from 0.2% to 0.35% vanadium (V)from 0.07% to 0.20% niobium (Nb)from 0.05% to 0.11% nitrogen (N.sub.2)less than 0.008% boron (B)and not more than the following residual percentages by mass:0.020% sulfur, 0.020% phosphorous, 0.025% cobalt, 0.010% aluminum, 0.02% titanium, 0.02% tin, 0.10% copper, 0.015% tungsten, 0.020% arsenic, and 0.0025% antimony;the remainder of the alloy being iron; said steel having a nickel equivalent calculated using the formula:Ni eq=30C+0.5Mn+2Ni+25N.sub.2 +40B,lying in the range 9 to 10.2;and a chromium equivalent calculated using the formula:Cr eq=Cr+2Si+1.5Mo+5V+1.75Nblying in the range 14.5 to 15.5;the ratio between the chromium equivalent and the nickel equivalent lying in the range 1.49 to 1.65.

Abstract: Percussion apparatus having a compressed air inlet (3) and serving to impart percussive movement to a tool (10), the said tool (10) sliding inside an envelope (1) fixed to the apparatus and being terminated by a spherical portion (22), includes the improvement wherein the said tool (10) includes a hollow tube (13) with one end (21) holding a ball (22) captive, which ball is urged against the end (21) by a spring (24) lodged in the tube (13). When the ball (22) is worn, it is easily changed.

Abstract: The apparatus is particularly intended for depositing chromium on the bearing surfaces of bearings and end stops of turbine rotors made of chromium steel in order to obtain a good coefficient of friction thereon. The apparatus comprises a vat (1) having a vertical axis 00' constituted by a cylindrical portion (2) terminated by a conical portion (3), said vat (1) being filled with electrolyte, first means (7, 8) disposed near the top of said vat (1) for feeding the vat (1) with electrolyte, second means (4) situated at the bottom of the vat (1) for emptying the electrolyte, third means (32, 33) situated between the second means (4) and the first means (7, 8) for regenerating and circulating the electroylte, fourth means (15) for supporting a curtain of anodes (17) made of the metal to be deposited and for rotating the electrolyte about the axis 00', and fifth means (29) for applying current of given polarity to the curtain of anodes (17 ).

Abstract: A method and apparatus for depositing a metal on a large-diameter cylindrical bore which passes right through the central portion of a large part. The invention consists in placing and centering the large part (1) between an upper tank (4) and a lower tank (3), so as to define a chamber (8) inside which the bore (2) is disposed and outside which the peripheral portions (9) of the part (1) extend, said chamber being filled with electrolyte. The electrolyte is homogenized and regenerated continuously outside the chamber (8) before being injected in the chamber (8) and before being entrained in a spirally descending motion to the level of the bore (2). The metal deposit takes place under the effect of a direct current which circulates between metal anodes (14) disposed in the bore (2) and the part (1) which serves as a cathode.The invention is used for depositing nickel on the bores of turbine rotor wheels so as to adjust dimensions or prevent fretting corrosion.

Abstract: A method and assembly for depositing a metal on a cylindrical bore which passes through the central portion of a large part. The invention consists in placing and centering the large part (1) between an upper tank (4) and a lower tank (3), so as to define a chamber (8) inside which the bore (2) is disposed and outside which the peripheral portion (9) of the part (1) extends, said chamber being filled with electrolyte. The electrolyte is homogenized and regenerated continuously by a current which flows between metal anodes (14) in the bore (2) and the part (2) serving as a cathode.The invention is used for depositing nickel on the bores of turbine rotor wheels so as to adjust dimensions or prevent fretting corrosion.

Abstract: The invention concerns welded turbine rotors. It is characterized in that, n the elements constituting a welded rotor which consist of a blade bearing block having at least one axial protuberance, that axial protuberance is made of steel having a lower carbon and nickel content than the remainder of the element and is joined thereto by a transition zone also made of steel. The invention applies more particularly to high-power steam turbines.

Abstract: The invention concerns welded turbine rotors. It is characterized in that, n the elements constituting a welded rotor which consist of a blade bearing block having at least one axial protuberance, that axial protuberance is made of steel having a lower carbon and nickel content than the remainder of the element and is joined thereto by a transition zone also made of steel. The invention applies more particularly to high-power steam turbines.