RU2579598C2 - Method for making jet forming nozzles - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to the production of jet forming nozzle that can be used for cleaning surfaces, removal of coatings on the roughened surface, for cutting and separation of materials. Method comprises forming a working hole in the composite diamond material produced under high pressure and temperature using a binder material, and final processing of the working opening, after which it is subjected to nitriding, wherein the composite diamond material contains a diamond phase and a binder comprising nickel and titanium when the content of titanium in an amount of 5.0-15.0 wt.%, and nitriding is conducted in pure nitrogen at a pressure of 1.2-1.5 atm, a temperature of 700-900 °C for 1-15 hours.

EFFECT: technical result achieved in the present invention is to increase the jet forming nozzle life by improving wear resistance of the working of the walls of the nozzle opening, as well as to ensure the preservation of compactness abrasive stream for a longer time, resulting in improved performance jet forming nozzle at gas and water-jet processing of materials.

5 cl, 1 ex

Description

The field of technology. The invention relates to the field of production of jet-forming nozzles, which can be used, for example, for cleaning surfaces, removing coatings, creating surface roughness, for cutting and separation of materials.

The prior art. Structuring is usually carried out by supplying water or gas under high pressure through a nozzle with a small hole. Depending on the type of treatment, abrasive fillers may be introduced into the stream. For accurate and efficient material processing, the nozzle must form a compact, well-focused jet and maintain its compactness for a long time. On the walls of the nozzle orifice during the passage of an air or water jet, a near-wall turbulent layer is formed, which has an inhibitory effect, which violates the parallel flow. Therefore, the processing quality of the working hole has a significant impact on the formation of a compact jet. In addition, as a result of the abrasive action of the jet on the walls of the nozzle’s working hole, abrasion of the walls occurs, the traces of wear appear on the latter, leading to a violation of the compactness of the jet, to a loss of pressure and an increase in resistance forces. In this case, you need to replace the nozzle with a new one. It should also be borne in mind that the nozzle is an expensive element in jet forming devices, so frequent replacement of the nozzle leads to an increase in the cost of blasting.

It is obvious that the wear resistance of the nozzle to a greater extent depends comprehensively on the material from which it is made, and on the type of processing to which the nozzle material is subjected during its manufacture.

It is known that for the manufacture of nozzles, various polycrystalline superhard materials are used containing diamond powders and a binder medium. Such materials have high hardness, due to the high content of diamond powders in them, they have a low coefficient of friction, high thermal conductivity, high wear resistance and, accordingly, have high durability.

A known method of producing polycrystalline diamond (RU 1029555, published. 07/20/1999), which includes the action of ultra-high pressure at high temperature on a hollow billet of carbon-containing material with a metal catalyst placed in it. In order to increase the abrasion resistance and the size of polycrystals, a refractory material is additionally introduced into the cavity of the preform in an amount of 4-90% of the volume of carbon-containing material. Refractory material is selected from the group: titanium, hafnium, vanadium, zirconium, niobium, molybdenum, tantalum, tungsten, rhenium, chromium, their alloys or compounds with carbon, nitrogen or silicon, graphite-like boron nitride, aluminum oxide.

The disadvantage of this material is the practical impossibility of its use in the manufacture of nozzle tools due to the significant diameter of the defective region of the composite (2.5-4 mm) compared with the diameter of the nozzle of the tool (0.2-1 mm).

Known heat-resistant composite diamond sintered material (RU No. 2312844, published. 2003), which can be used both in cutting tools, and also as a wear-resistant material operating in friction conditions. The material is obtained at high pressures (P = 7.7 GPa) and high temperatures (T = 2100 ° C) by sintering diamond powders with grain sizes less than 200 nm without the use of a sintering additive. The material can be given a different configuration through laser or EDM, grinding and polishing. Since there is no binder in the material, it has a high hardness of 85 GPa according to Vickers and high wear resistance.

The disadvantage of the material is that for its manufacture requires a sufficiently high pressure and very high temperatures. Equipment that implements these conditions does not allow the manufacture of large-sized material; therefore, the material has a narrow range of applications.

A known method of manufacturing a nozzle (US 2002142709, published. 2002). For the manufacture of the nozzle, wear-resistant sintered polycrystalline diamond material obtained using high pressures and temperatures is used. The material is made by sintering diamond powders in the presence of a catalyst. The catalyst can be presented in the form of a powder, which is mixed with diamond powder, or the catalyst can be introduced into the layer of diamond powder by impregnation. As a binder catalyst, cobalt or an alloy of cobalt, for example, with nickel, can be used. The material has sufficient wear resistance and electrical conductivity. Sintered diamond material is processed using spark or laser cutting or other types of processing to obtain external dimensions. In the resulting workpiece by electric spark drilling, a working hole is formed and processed by grinding and polishing.

The disadvantage of this method is as follows. The structure of the sintered diamond material is diamond grains, bonded to each other by a binder material, the physical and mechanical characteristics of which are significantly inferior to diamond. When operating the nozzle, the walls of the working hole under the influence of an abrasive-containing jet passing through this hole under high pressure will be subject to wear. In this case, wall wear will occur locally over the entire surface in those places where the metal phase is located, forming the so-called erosion. The presence of erosion on the surface of the working hole violates the straightness of the flow, turbulence forms in the water or gas flow, which violate the compactness of the jet, as a result, its speed decreases, and the energy loss increases. All this leads to a decrease in the efficiency of processing parts.

The prototype of the proposed invention is a method of manufacturing a jet-forming nozzle (WO 2008032272, published. 2008) from a polycrystalline diamond material containing cobalt, silicon and silicon carbide as a binder using an ultra-high pressure synthesis apparatus. A working hole is formed in a diamond polycrystal using laser drilling, which is processed to obtain the required dimensions and polished to obtain the final dimensions and surface quality of the hole. Polishing is mainly carried out using copper or steel wire in the presence of a fine-grained diamond powder.

The disadvantage of this method is the presence of silicon, which during crystallization increases its volume, which leads to the appearance of microstresses and in the future to the occurrence of microcracks. In the process of manufacturing a nozzle or other type of tool under loads, cracking and violation of the integrity of the polycrystals occur.

Disclosure of the invention. The technical problem to which the proposed invention is directed is to develop a method for manufacturing a jet-forming nozzle, in which an increase in the service life of the jet-forming nozzle is achieved by increasing the wear resistance of the walls of the nozzle working hole, and the compactness of the abrasive-containing stream is maintained for a longer time, which leads to an increase the efficiency of the jet forming nozzle during gas and waterjet processing of materials.

The specified technical result is achieved in the invention as follows.

A method of manufacturing a jet forming nozzle includes forming a working hole in a composite diamond material obtained under conditions of high pressures and temperatures using a binder material, and final processing of the working hole, after which it is subjected to nitriding.

In this case, the composite diamond material contains a diamond phase and a phase of a binder comprising nickel and titanium with a titanium content in the amount of 5.0-15.0 wt.%.

In the particular case, nitriding is carried out in a nitrogen-containing medium at a temperature of 700-900 ° C for 1-15 hours

In addition, nitriding is carried out in pure nitrogen.

Composite diamond material is also obtained by synthesis from a carbon-containing material in the field of thermodynamic stability of diamond in the presence of a binder.

In addition, the binder material contains titanium in an amount of 5.0-10.0 wt.%.

Composite diamond material is also obtained by sintering diamond powders in the presence of a binder.

In addition, a composite diamond material is obtained by impregnating diamond powders with a melt of a binder.

Embodiments of the invention. The method is as follows.

For the manufacture of nozzles using polycrystalline diamond materials, which are obtained using various technologies. One of the methods for producing polycrystalline diamond material involves mixing diamond powder with metal catalyst powders, placing the mixture in a device in which high pressure and temperature conditions are created that provide catalytic reactions and the bonding of diamond particles to each other.

Another method for producing a polycrystalline material involves placing in the form of a diamond powder and compacting the powder by any known method, for example by pressing, vibration compaction, etc. To obtain a material with a high volumetric content of diamond powder, diamond powders of different grain sizes can be used, while the grain size of the powders is chosen so that finer grain powders were placed between diamond granular powders. Impregnating material is placed on compacted powders and impregnation is carried out under pressure at a temperature providing the required fluidity of the impregnating material.

Polycrystalline material can also be obtained by forming a preform of carbon-containing material, which is impregnated with a metal or alloy catalyst under high pressure and temperature. In this method, the metal catalyst is formed in the form of a rod, in contact with which is a carbon-containing material. The impregnation is carried out at a pressure above 7 GPa and at a temperature that ensures the fluidity of the catalyst, at which it completely seeps into the volume of the graphite billet. The impregnation temperature depends on the composition of the catalyst. Nickel or its alloys with metals are used as a catalyst: titanium, molybdenum, chromium. The carbon-containing material is graphite. Under the conditions of synthesis, the formation of diamond occurs, which begins at the contact surface of the carbon-containing material with the rod and extends into the depth of the carbon-containing material such as "carbonado" or "ballas".

In all of the above cases, the composite diamond material contains a diamond phase and a binder phase comprising nickel and titanium with a titanium content of 5.0-15.0 wt.%.

Nickel - titanium alloy has high strength with satisfactory ductility. Exceeding the titanium content leads to embrittlement of the matrix, thereby reducing the strength properties of the composite as a whole. Less titanium complicates the process of subsequent nitriding.

To make a nozzle, a working hole is formed in a diamond polycrystal. Since the polycrystal with a nickel binder is electrically conductive, the working hole can be formed by electric spark machining, laser drilling, as well as any known suitable method.

After receiving the holes produce its multi-stage processing. First, rough grinding of the hole is performed with a tool in the form of a wire or a needle in the presence of coarse-grained diamond powder. Then, the holes are ground with fine-grained diamond powder.

The hole is polished until a smooth surface is obtained, which contributes to the formation of a compact gas and hydroabrasive jet with constant pressure and which has a high flow rate from the working hole without crushing and spraying.

After the working hole has been finally processed, the working hole is subjected to a nitriding process. It is technologically more convenient to expose the entire nozzle to the nitriding process. When nitriding, diffusion saturation is subjected to areas that are of a metallic nature. Such areas are areas of the matrix material, which are metals or catalyst alloys. Since a diamond polycrystal containing a binder in the form of a nickel-titanium alloy was used as the material for the nozzle, the surface of the hole wall contains sections of this alloy.

These areas undergo diffusion saturation with nitrogen to form a nitride layer. The formation of a nitride layer helps to increase the hardness and wear resistance of these sections, making a smaller difference in physical and mechanical properties between the sections of the binder and the sections of diamond material. In general, the wear resistance of the wall of the working hole increases, resistance to the appearance of scoring and cavitation effects, and the corrosion resistance of the nozzle in water and air is increased.

To carry out the nitriding process, the nozzle is placed in a furnace, nitrogen is supplied to the furnace, and heated to a temperature of 700-900 ° C. Since the nozzles have small overall dimensions, chamber furnaces can be used for nitriding.

Pure nitrogen is preferably used for nitriding. Ammonia or a mixture thereof with nitrogen may be used. But in this case, the nitride layer will become somewhat brittle.

In nitrogen, the nozzle is kept for 1-15 hours. At this temperature, for 1-15 hours, a nitride layer is formed on the surface of the wall of the working hole, the thickness of which is 35-40 nm. A nitride layer of this thickness does not violate the surface relief of the walls of the working channel, while maintaining its smoothness, does not exfoliate from the surface.

An increase in the nitriding time will lead to an increase in the coating thickness and its peeling from the matrix region due to various coefficients of thermal expansion, including those associated with the diamond content on the nitrided surface. Reducing the nitriding time will lead to a decrease in the layer thickness. With a small layer thickness, the required continuity and density will not be obtained.

An increase in temperature above 900 ° C will lead to an increase in the rate of nitriding, but will also cause graphitization of diamond compact grains and a decrease in abrasion resistance. Lowering the temperature below 700 ° C will lead to a significant increase in the nitriding time and to an unreasonable decrease in the productivity of the nitriding process.

Example

Several diamond composites were prepared by synthesis from graphite at a pressure of 9.0 GPa and a temperature of about 1700 ° C for 10 s. In the synthesis, an alloy-catalyst composition of nickel - 10% titanium was used. The size of the composite is 4 mm in diameter and 4 mm in height. Of diamond composites, diamond grinding was used to make disks with a thickness of 2 mm and a diameter of 4 mm. A nozzle with an outer diameter of 2 mm and an opening diameter of 0.3 mm was laser cut from these disks. Next, the hole was machined and polished to achieve a roughness of Ra = 0.32. Nitriding was carried out at a nitrogen pressure of 1.2-1.5 atm, at a temperature of 850 C for 3 hours. The thickness of the nitride coating on the metal sections of the diamond composite reached 30-40 nm. The surface roughness in comparison with the initial roughness did not change. On other polycrystals, the nozzle was nitrided at a temperature of 700 ° C. The nitriding time to obtain a dense continuous coating was 15 hours. A further decrease in the nitriding temperature is ineffective, since it will take a lot of time to obtain a nitride layer 30–40 nm thick.

Diamond composites were made using a nickel - 20 wt.% Titanium catalyst. A large amount of titanium led to embrittlement of the polycrystal; the strength characteristics of such a nozzle were significantly reduced.

Composites, which were synthesized using a catalyst of the composition nickel - 5% titanium, retained their integrity and were used for the manufacture of nozzles. To obtain a dense nitride layer, the nitriding time was 15 hours. A decrease in the titanium content below 5 wt% complicated the nitriding process; an increase in the wear resistance of such nozzles was insignificant.

The nozzles made in accordance with the invention were tested during water-jet cutting at a pressure of 3800 atm of steel sheets 20 mm thick. The possibility of forming a compact jet was evaluated visually. Excessive spray spray for nitrided nozzles was not observed. The cutting ability of the waterjet jet was evaluated by the cutting speed of the steel plate. The cutting speed when using nitrided nozzles was 20% higher than that of non-nitrided ones, the resistance of nitrided nozzles exceeded the resistance of non-nitrided nozzles by 40-60%.

Claims (5)

1. A method of manufacturing a jet-forming nozzle, including the formation of a working hole in a composite diamond material obtained under high pressure and temperature using a binder material, and the final processing of the working hole, after which it is subjected to nitriding, while the composite diamond material contains a diamond phase and phase a binder, including Nickel and titanium with a titanium content in the amount of 5.0-15.0 wt.%, and nitriding is carried out in a medium of pure nitrogen at a pressure of 1.2-1.5 atm, erature 700-900 ° C for 1-15 hours. 2. The method according to claim 1, in which the composite diamond material is obtained by synthesis from a carbon-containing material in the field of thermodynamic stability of diamond in the presence of a binder material. 3. The method according to claim 2, in which the binder material contains titanium in an amount of 5.0-10.0 wt.%. 4. The method according to claim 1, in which the composite diamond material is obtained by sintering diamond powders in the presence of a binder material. 5. The method according to claim 1, in which the composite diamond material is obtained by impregnating diamond powders with a melt of a binder.