Abstract: Provided is a titanium cast product for hot rolling made of commercially pure titanium, the titanium cast product including a melted and resolidified layer in a range of more than or equal to 1 mm in depth on a surface serving as a rolling surface, the melted and resolidified layer being obtained by adding one or more elements out of any one of or both of at least one ? stabilizer element and at least one neutral element to the surface, and melting and resolidifying the surface. An average value of a total concentration of the at least one ? stabilizer element and the at least one neutral element in the range of more than or equal to 1 mm in depth is higher than a total concentration of the at least one ? stabilizer element and the at least one neutral element in a base metal by, in mass %, more than or equal to 0.1% and less than 2.0%.

Abstract: A lamination molding apparatus is provided capable of preventing damage to a cutting device. Every time a sintered body including a sintered layer group consisting of a predetermined number of sintered layers is formed, gas is injected from a gas injector toward a vicinity of a side surface of the newly formed sintered body so as to blow off material powder, and then the side surface of the sintered body is shaved by a cutting tool of the cutting device, wherein the gas injector blows off the material powder by only intermittent injection which repeats short-time gas injection or by a combination of the intermittent injection and continuous injection which continuously injects the gas.

Abstract: A wave gear device includes a circular spline that has an annular shape and rigidity; a flex spline that has an annular shape and flexibility, and is disposed in the circular spline; and a wave generator that is disposed in the flex spline, is configured to cause the flex spline to be distorted in a radial direction and is configured to partially mesh with the circular spline, and is configured to move a meshing position between the circular spline and the flex spline in a circumferential direction. The ratio of the Vickers hardness on an inner circumferential surface of the flex spline to the Vickers hardness on an outer circumferential surface of the wave generator is 1.2 or more and 1.7 or less.

Abstract: A method of hardfacing a component includes generating a laser beam and directing the laser beam to an area of a wear surface of the component. The method includes feeding a flexible cord of a cladding material into the laser beam to melt the flexible cord and produce a bead of the cladding material on the wear surface. The flexible cord includes an inner metal wire surrounded by an agglomerate of abrasion and wear-resistant material that contains diamond particles. The method further includes moving the laser beam and the flexible cord along the wear surface to produce a cladding layer over the wear surface of the component.

Abstract: A method of manufacturing a recirculating ball nut for a ball screw drive, comprising a base body which includes at least one recirculating ball track, the method comprising the following manufacturing steps: manufacturing the base body by precision forging; and finishing the recirculating ball track by a cutting method subsequent to manufacturing the base body.

Abstract: A radial piston machine includes at least one piston unit with a piston and at least one rolling element rotatably mounted in a rolling element receptable of the piston. The piston of the piston unit is polished.

Abstract: Various embodiments include apparatuses adapted to be used as a replacement oil cartridge tip. In some embodiments apparatuses include a replacement swirler ring for an oil cartridge tip, the replacement swirler ring having an annular main body including an inner diameter surface sized to be joined to an outer diameter surface of the oil cartridge tip by a metal joining process including one of brazing, welding temperature or mechanical interference and an outer diameter surface including channels evenly spaced about a primary axis of the annular main body, wherein the annular ring includes a material that is at least as wear-resistant as a material of the oil cartridge tip.

Abstract: A method of manufacturing a solid oxide fuel cell stack having an electrically conductive interconnect, including the steps of: (a) providing a first fuel cell and a second fuel cell, (b) providing a substrate having an iron-chromium alloy, (c) depositing a layer of metallic cobalt over a portion of substrate surface, (d) subjecting the layer of metallic cobalt to reducing conditions, (e) then exposing the remaining portion of the layer of metallic cobalt to oxidizing conditions for a predetermined time and temperature, such that the surface portion of the layer of metallic cobalt is oxidized to cobalt oxide, thereby forming the electrically conductive interconnect having a layer of metallic cobalt sandwiched between a surface layer of cobalt oxide and the layer of cobalt-iron-chromium alloy, and (f) sandwiching the substrate between the first and second fuel cells.

Abstract: A method for fabricating crystalline surface structures (4) on a template (1). The method comprises the steps of providing a template (1) into a reaction environment, wherein one or more elements (3) required for the formation of the crystalline surface structure (4) are contained within the template (1); heating the template (1) inside the reaction environment to increase the mobility of the element (3) within the template (1), and to increase the surface diffusion length of the element (3) on the template-environment interface; and activating the template (1) by altering the conditions within the reaction environment, to make the mobile element (3) slowly migrate towards the template-environment interface and to make the element (3) organize on the surface of the template (1) as a crystalline structure (4).

Abstract: Polysilicon rods from the Siemens process are crushed into fragments and further processed to fragments having very low metal contamination in an economical manner by purposefully fabricating parts contacting the polysilicon from materials which cause high metal contamination, and removing the metal contamination by a cleaning bath or baths tailored to the particular metal contamination. By this process, economical materials previously scrupulously avoided, such as low alloy steel, can be used for crushers, conveyors, and other polysilicon-contacting parts of the crushing and classifying system.

Abstract: Methods for depositing low resistivity tungsten in features of substrates in semiconductor processing are disclosed herein. Methods involve using a germanium-containing reducing agent during tungsten nucleation layer deposition to achieve thin, low resistivity nucleation layers.

Abstract: An agricultural auger for conveying grain material is provided. The agricultural auger includes a shaft that is adapted to rotate about a central axis. A flight extends and spirals about the shaft. The flight further includes a base material of a first hardness. A laser treated material is formed on or into the base material along a portion of the flight. The laser treated material comprises a second hardness greater than the first hardness.

Abstract: A direct manufacturing technique involving rapid solidification processing uses a reaction between a metallic molten pool and a reactant gas in an inert atmosphere to form alloys with improved desired properties. By utilizing rapid solidification techniques, solubility levels are increased resulting in alloys with unique mechanical and physical properties. Laser deposition of alloys in atmospheres of varying reactant content produce compositions with intermingled and significantly improved overall properties.

Abstract: A method for producing a piston for an internal combustion engine, composed of first and second piston components, has the following steps: (a) providing a blank of the first piston component composed of a tempered or precipitation-hardened steel, having at least one joining surface, (b) providing a blank of the second piston component composed of a tempered or precipitation-hardened steel, having at least one joining surface, (c) tempering or precipitation-hardening the blanks, (d) friction-welding the joining surfaces of the blanks to produce a piston blank, with the formation of at least one friction-welding seam and a heat influence zone in the region of the at least one friction-welding seam, (e) annealing or low-stress annealing of the piston blank, thereby obtaining the heat influence zone(s), (f) re-machining and/or finishing the piston blank to produce a piston. A piston so produced is also provided.

Abstract: A variable hardness gradient armor alloy is produced with a liquid-state reaction between a metallic molten pool and a gaseous atmosphere having a small fraction of reactive gas. The content of the reactant gas is varied as the armor is fabricated in order to vary the properties of the resultant material across its thickness and typically include, for example, a hardened outer or initial layer for impact resistance, and at least one inner layer having a lower hardness than the outer layer but greater energy absorption.

Abstract: A method for producing a torque transmission device such as a fixed constant velocity ball joint constructed as an opposed track joint in which the curvatures bases of the tracks of the joint deviate in their axial course from the curvatures of the ball contact lines. The method is characterized in that prior to the formation of a longitudinal profile of a joint component, the component is brought to an increased hardness by a hardening process and a diffusion layer is partially or completely removed in the region of the longitudinal profile.

Abstract: Provided are novel multidimensional electrode structures containing high capacity active materials for use in rechargeable electrochemical cells. These structures include main support structures and multiple nanowires attached to the support structures and extending into different directions away from these supports. The active material may be deposited as a layer (uniform or non-uniform) surrounding the nanowires and, in certain embodiments, the main supports and even substrate. The active material layer may be sufficiently thin to prevent pulverization of the layer at given operating conditions. Interconnections between the electrode structures and/or substrate may be provided by overlaps formed during deposition of the active layer. Silicide-based nano wires structures may be formed on the main supports in a fluidized bed reactor by suspending the metal-containing main supports in a silicon-containing process gas. A layer of silicon may be then deposited over these silicide nanowires.

Abstract: The present invention provides a constant velocity universal joint component and a manufacturing method thereof capable of achieving increased strength without significant procedural changes, and that can contribute to size reduction and weight reduction. In the constant velocity universal joint component of the present invention, a sharp-angled portion 15 is formed by machining after cold plastic working is applied. A carburization process is then performed in which surface carbon concentration of 0.45 mass % to less than 0.60 mass % is obtained. Quenching is then performed. High-frequency induction hardening is subsequently performed.

Abstract: A method of manufacturing a ceramic/metal composite structure includes the steps of: performing a multi-stage pre-oxidizing process on the copper sheet; placing the copper sheet on a ceramic substrate; and heating the copper sheet and the ceramic substrate to a joining temperature to join the copper sheet and the ceramic substrate together to enhance interface strength between the copper sheet and the ceramic substrate according to the multi-stage pre-oxidizing process. The multi-stage pre-oxidizing process includes a first stage of pre-oxidizing process and a second stage of pre-oxidizing process, and the first and second stages of pre-oxidizing processes are performed in atmospheres with different oxygen partial pressures and at different temperatures.

Abstract: The performance of a worm assembly seal is improved by (1) the use of a hardened steel worm with a bronze worm gear; (2) a tribological coating on one or both of the worm thread or spiral and the gear teeth; 3) a tribological coating on one or both of the input or output shaft or shaft sleeves; or (4) a tribological coating applied to the worm thread, the gear teeth, the input and output shafts or shaft sleeves, or combinations thereof. In each of the approaches, the worm, worm gear, and input and output shafts or shaft sleeves can have surface finishing treatments. Additionally, in each of the three approaches, carbon or carbon/nitrogen concentration gradients can be added to the worm.

Abstract: Grooves as ball rolling grooves are formed in a side peripheral wall of a preparatory formed body that is to be an inner member. A recess opened so as to be continuous to curved bottom sections of the grooves, which face a through-hole, is formed in one end surface of the preparatory formed body. In carburizing, carburizing gas entering into space between the through-hole and a support shaft member flows through the recess after coming into contact with inner teeth, and is then discharged to the outside of the preparatory formed body via the curved bottom sections of the grooves. On the contrary, the carburizing gas having been in contact with the curved bottom sections of the grooves flows through the recess to come to be in contact with the inner teeth and is then discharged through the space.

Abstract: A blade made of a carbon steel or alloy steel is subjected to a surface nitriding process to form a high hardness nitride layer having a thickness in the range of 10 ?m to 100 ?m and a Vickers hardness Hv of 1000 or more, and a silver oxide layer, a copper oxide layer, or a silver oxide and copper oxide layer is formed on the high hardness nitride layer of the blade by firing. Through this processing, the blade that has a high cutting maintaining ability and an excellent sanitization ability such as antibiosis, sterilization ability, and antimold ability is provided.

Abstract: The invention relates to case-hardening of a stainless steel article by means of gas including carbon and/or nitrogen, whereby carbon and/or nitrogen atoms diffuse through the surface into the article. The method includes activating the surface of the article, applying a top layer on the activated surface to prevent repassivation. The top layer includes metal which is catalytic to the decomposition of the gas.

Abstract: The present invention relates to a method of and an apparatus for forming a thin metal film of copper, silver, or the like on a surface of a semiconductor or another substrate. A method of forming a thin metal film, comprises preparing a dispersed liquid having a metal-containing organic compound dispersed in a predetermined solvent, coating the dispersed liquid on a surface of a substrate and evaporating the solvent to form a coating layer, and applying an energy beam to the coating layer to decompose away an organic substance contained in the coating layer in an area irradiated with the energy beam and bond metal contained in the coating layer.According to the present invention, it is possible to form a thin metal film of good quality efficiently and stably. The thin metal film used as metal interconnects in highly integrated semiconductor circuits contributes to the progress of a process of fabricating semiconductor devices.

Abstract: A cast-bonding process includes a magnesium coating step and a magnesium nitride-forming step. The magnesium-coating step is carried out by supplying gasified magnesium into a mold in which a cast-in insert formed from an aluminum alloy, or an aluminum-based composite material is set, so that magnesium may coat the insert. The magnesium nitride-forming step is carried out by supplying nitrogen gas into the mold so that the coating magnesium and nitrogen gas may react to form magnesium nitride. Then, a molten aluminum alloy is poured into the mold for cast-bonding the insert.

Abstract: The present invention relates to a surface hardened and coated stainless steel said surface showing low static friction and with improved wear resistance. Moreover, it relates to a coating of the surface of said stainless steel, in which a surface hardening is accomplished simultaneously with said coating. The resulting coated steel showing a very high hardness simultaneously as it shows improved adherence. Said steel advantageously being used in applications with high requirements regarding a combination of high strength and/or toughness and wear resistance together with low friction, such as, e.g., shock absorbers and items for combustion engines and hydraulic systems, produced with a highly cost effective process.

Abstract: According to the method of the present invention, the ball plug is press fit into the counterbored passage of a fuel injector nozzle assembly prior to hardening of the fuel injector nozzle assembly. A core hardening and gas nitriding process is then applied to the assembly, causing the ball plug to expand and the passage diameter to shrink.

Abstract: A method for manufacturing a clad component in which a cladding workpiece having a section comprising a first metal onto which a number of metal beads are rigidly bonded is inserted into a mold. A molten second metal is poured into the mold, where it flows about and covers the beads and is then permitted to cool. This process forms an article made of the second metal, which is mechanically interlocked to the beads, clad by the first metal. Typically the first metal is a high-melting point strong metal, such as steel, and the second metal is a lower-melting point, weaker, but lighter metal, such as aluminum.

Abstract: A thread for expandable downhole tubular connections is disclosed. The thread on at least one of the pin and box is coated, preferably with an anti-galling compound. During expansion the coating crumbles and the particles in between the threads keep the joint from becoming undone despite longitudinal shrinkage from the expansion or any tendency of the swage to impart a rotational motion on one part of the joint during the expansion process.

Abstract: A thin film of metal or metal compound is produced by preparing an ultrafine particle dispersion liquid by dispersing ultrafine particles at least partly made of metal into a given organic solvent, applying the ultrafine particle dispersion liquid to a substrate, drying the ultrafine particle dispersion liquid to leave metal or metal compound particles on the substrate, heating the metal or metal compound particles to join the metal or metal compound particles, and annealing the metal or metal compound particles into a thin film.

Abstract: The invention provides a substantially uniform layer of a boride or a carbide of a refractory metal metallurgically bonded on a substrate of a workpiece. A layer of the refractory metal is deposited on the substrate. At least one of the elements boron and carbon is deposited from a source other than the workpiece on the workpiece having the refractory metal layer. The workpiece is heated at a temperature and for a time period sufficient to diffuse at least a portion of the deposited refractory metal into the substrate and at least a portion of the deposited boron or carbon into the refractory metal layer and the substrate to form a substantially uniform layer of the boride or carbide of the refractory metal metallurgically bonded on the substrate.

Abstract: A laminated ring for use as a belt in transmitting power in a continuously variable transmission is produced by welding opposite ends of a sheet of maraging steel to produce a plurality of rings, and rolling said rings to a predetermined length. The rings are nitrided in a salt-bath nitriding process by dipping the rings in a molten salt containing 38-46% of CNO− and 1-2% of CN− and heated to a temperature in the range from 480 to 530° C., for a period of time ranging from 10 to 25 minutes. The nitrided rings are finally stacked into a laminated ring.

Abstract: A steel part, such as a mechanical centrifuge screen of mild steel with a nitriding layer on all exposed surfaces of the steel to form an effectively hardened substrate layer, and electroplating the nitrided steel part. The surface treatment method provides an improved wear resistance and effectively provides improved erosion and corrosion protection of the steel part.

Abstract: A rotary compressor comprises a cylinder having an inner space and a groove, a roller sliding along the inside of the inner space of the cylinder, a vane penetrating through the groove, and refrigerant. The groove penetrates through the outside and inner space of the cylinder. The vane slides on the roller, and the vane also slides in and out of the groove. The vane includes stainless steel formed by sintering of powder material, a nitrogen diffusion layer disposed on the surface of the stainless steel, and a compound layer of iron and nitrogen disposed on the surface of the nitrogen diffusion layer. The stainless steel has a plurality of fine pores formed by sintering of powder material. The plurality of fine pores have a porosity of 15% or less.

Abstract: A threaded steel coupling with an exterior coating and interior case and threads, wherein the coupling body consists primarily of bainite and the interior case and threads consist primarily of a mixture of martensite and bainite. Also provided is a method of fabrication, including selective carburization of the interior threaded portion of the steel coupling forming the case and austempering.

Abstract: A ball for use in a constant-velocity joint, which is adapted to be interposed between an inner race and an outer race for transmitting rotational power therebetween, is produced by nitriding a surface of a ball made of bearing steel or a material equivalent thereto, and processing the nitrided ball for increased resistance to a crushing load. The nitrided ball is processed for increased resistance to a crushing load by tempering the ball at a temperature ranging from 180 to 230° C. The surface hardness of the ball should preferably be adjusted in the range from HRC 60 to 64.

Abstract: A nickel-base superalloy article substrate has more nickel than any other element and a nominal bulk composition of carbon. A protective layer is deposited overlying the surface of the article substrate. The protective layer includes aluminum and one or more of the reactive elements hafnium, zirconium, yttrium, lanthanum, and cerium. The depositing of the protective layer includes steps of decarburizing locations where the carbon may serve as a barrier to the mobility of the reactive elements within the protective layer, and depositing an aluminum-containing protective layer overlying the substrate. The decreasing of the carbon concentration may be accomplished. by decarburizing the substrate, depositing a platinum-containing layer and then decarburizing, depositing an aluminum-containing layer in a reducing atmosphere, and/or decarburizing the deposited protective layer. A ceramic thermal barrier coating may be deposited overlying the protective layer.

Abstract: A method for improving the corrosion resistance, increasing the hardness, providing superior ductility, and reducing surface-cracking of a diffusion coating by nitriding and heating-treating the diffusion coating is disclosed. The nitriding and heat-treating may occur subsequently or simultaneously. Further, the disclosed method may be practiced subsequent to or incorporated as an intergral part of any known diffusion coating process which utilizes a heating step in a furnace having a cover gas.

Abstract: A method of aluminum diffusion coating the surface of an iron-, nickel-, cobalt-, or titanium-base alloy product begins with cleaning and providing an anchor profile on the surface of the product, followed by depositing with an appropriate thermal spray method at least 4 mils (0.1016 millimeters) thickness of a minimum 85 wt. % aluminum alloy, which can also contain up to 12 wt. % silicon. A MCrAlX-type coating layer is also thermally sprayed on the substrate surface before the aluminum alloy is sprayed. The thermal sprayed products are heat treated in a sealed retort at a temperature of between 900.degree. F. and 1200.degree. F. (482.degree. C. and 649.degree. C.) and then maintained at that temperature for a period of at least one hour to ensure the formation of a strong metallurgical bond between the aluminum alloy layer and the product. The retort temperature is then elevated to between 1400.degree. F. and 2000.degree. F. (760.degree. C. and 1093.degree. C.) and held at that temperature for between 0.

Abstract: A method for case hardening a chromium bearing nickel or ferrous based alloy, for example stainless steel, article, the method including the steps of activating the surface of the article; and carburizing the activated surface at a temperature below that temperature which would promote the formation of carbides. In one embodiment the surface is activated by disposing a layer of iron over the surface of the article.

Abstract: By forming a Cr playing layer on the surface of a metal and forming a CrN film by nitriding the surface thereof, it is possible to improve the surface hardness, wear resistance, corrosion resistance, etc., of the metal; wherein the nitriding treatment of the Cr plating layer surface is carried out by a method of heating in a nitrided atmosphere, preferably heated in a nitrided atmosphere which includes an ammonia decomposed gas treated in advance with an ammonia decomposition catalyst as a nitrogen source; in addition it is preferable that before the nitriding treatment, the Cr plating layer surface is purified and activated by heating in a halogen compound or a reacting gas which includes halogen.

Abstract: A surface treating is performed by an electric discharge. The electric discharge is generated by applying a voltage between an electrode and a metal workpiece. The electrode is a solid or green compact electrode or the like which is made of a reforming material. The workpiece may be an end mill or the like. Then, a coating layer is formed on a surface of the metal workpiece. Thereafter, a nitriding treatment is performed on the coating layer in a nitriding vessel or the like. Thus, a hard coating layer of better quality is formed on the surface of the workpiece whether a material of the workpiece is steel or hard metal.

Abstract: The adhesive strength and hardness of chromium nitride(CrN) film deposited on SKD 61 tool steel was significantly enhanced by a nitriding process on the surface the tool steel before coating with a CrN film. These nitriding processes included nitrocarburing, gas nitriding, and plasma nitriding, respectively. After nitriding, the surface of tool steel was repolishing with grits #600, #1000, #1800 of SiC grinding paper, as well as #1000 grinding paper and diamond paste, respectively. After repolishing, the CrN film was deposited by the cathodic arc ion plating deposition process at low temperatre of 200.degree. C. The present invention was related to the process modification for enhancing the adhesive strength and surface hardness of CrN film deposited on tool steels. This method included a nitriding process and a repolishing followed by the cathodic arc ion plating deposition.

Abstract: Brazing alloys used in a method of brazing at least two steel components into an integral part during a carburizing treatment followed by a quenching treatment are disclosed. These alloys should be in a liquid phase during the carburizing process in which the steel components with a brazing alloy placed therebetween are carburized at a temperature of approximately 930.degree. C., and in a solid phase at a temperature of approximately 850.degree. C. attained immediately before the quenching treatment. A Cu--Mn brazing alloy containing at least from 55 to 80 weight % of copper and from 20 to 45 weight % of manganese or a Cu--Mn--Ni brazing alloy containing at least from 20 to 45 weight % of manganese and from 0 to 15 weight % of nickel are suitable for the simultaneous brazing and carburizing process.

Abstract: Object: Prevention of generation of press marks as well as increase of wear resistance at a corrugation tip portion and thereby providing a corrugating roll having a much improved life.Construction: A manufacturing method of a corrugating roll useful for forming a wave-shaped core paper of corrugated board, characterized in that the corrugating roll is worked to form tooth-shaped corrugation portions on the outer circumference and applying a nitriding treatment or a carbo-nitriding treatment, and then applying to the corrugation portion of the corrugating roll a quenching and tempering treatment, and further forming a wear resistant coating on the surface of the corrugation portion.

Abstract: A method of applying a surface coating to promote gas carburization of a highly alloyed steel. The method includes the step of coating the highly alloyed steel with a layer of iron or an iron alloy to form a coated steel before carburizing the coated steel in a conventional gas carburizing atmosphere.

Abstract: A method of manufacturing an expansible anchor comprises the steps of forming one part as a partially slotted expansible sleeve composed of corrosion-resistant steel and anchorable in a building component, forming another part as an expander body composed of corrosion-resistant steel and arranged to be driven into the expansible sleeve so as to anchor the expansible sleeve in the building component, enriching one of the parts with interstitially dissolved, non-metallic alloying constituents selected from the group consisting of carbon, nitrogen and boron, and ageing by heat treating so as to precipitate the alloying constituents in the form selected from the group consisting of carbides, nitrides and borides, respectively, to achieve increased hardness.

Abstract: A process for the thermochemical treatment of thin-walled structural elements made of steel comprising enriching an edge zone of a thin-walled structural element with nitrogen and carbon at 590.degree. to 700.degree. C. to harden the edge zone whereby an intermediate layer (3) is formed in the diffusion zone (2), said intermediate layer comprising 1 to 3% by weight of nitrogen and at most 0.8% by weight of carbon and cooling the said thin-walled structural element under an inert atmosphere at a rate of 50.degree. to 100.degree. C. per minute to room temperature to form a nitrogen austenite and/or braunite phase between the connection layer (1) and the basic structure (4) with increased fatigue strength.

Abstract: In the preparation of a galvanized steel strip by continuously heating and anneal reducing a steel strip and subsequently admitting it, without contact with the ambient air, into a molten zinc bath to coat the strip with zinc, there is provided a method for preparing a galvanized or galvannealed steel strip having minimal uncoated defects, characterized in that a steel strip having a composition which containsup to 0.1% by weight of C,0.01 to 1.0% by weight of Si,0.05 to 2.0% by weight of Mn, andup to 0.15% by weight of P,and satisfies the following formula (1):Si/28+Mn/55+P/31.gtoreq.0.01 (1)wherein the element symbols represent the contents in % by weight of the respective elements in the steel strip is used as the starting strip to be galvanized, and the steel strip is subjected to carburizing treatment during the anneal reducing step or before the anneal reduced steel strip is admitted into the molten zinc bath.

Abstract: Precision ferrous metal parts subject to severe friction and corrosion in e are nitrided, preferably in a bath of molten salts based on CNO.sup.- cyanate ions, oxidized, preferably in baths of molten oxidizing alkaline salts, and then impregnated with a hydrophobic wax. A layer after the nitriding and oxidation steps is formed of a close-packed deep sub-layer and a porous superficial sub-layer ranging in thickness between 5 and 25 .mu.m, and exhibiting through pores ranging between 0.2 and 3 .mu.m in diameter. The impregnation wax is an organic compound with a high molecular weight between 500 and 10,000, with a surface tension in the liquid state ranging between 10 and 73 mN/m, the contact angle between the solid phase of the superficial layer and the wax in the liquid state ranging between 0 and 75.degree. C.