Cast Structural Element of a Pump, Filter or Compressor with Wear Resistant Layer Comprising Composite Material Based on Alloys Reinforced with Tungsten Carbide and the Method of Producing Thereof

Abstract

A cast structural element of a pump, filter or compressor is disclosed with wear resistant layer comprising in situ produced composite material based on alloys, especially cast iron based alloys, reinforced with tungsten carbide in the form of crystals and/or particles, characterized by the microstructure of the composite material within the layer comprising faceted crystals and/or faceted particles tungsten carbide that provide uniform macroscopic and microscopic distribution, wherein the crystals and/or particles of tungsten carbide include irregular and/or round and/or oval nano and/or micro-areas filled with alloy based on metal. A method of producing the cast structural element in the form of a pump, filter or compressor is also disclosed.

Claims

1. A cast structural element of at least one of a pump, filter or compressor together with a wear resistant in situ produced layer comprising; composite material based on alloys reinforced with tungsten carbide in the form of at least one of crystals and particles, a microstructure of the composite material within a layer comprises at least one of faceted crystals and faceted particles of tungsten carbide that provide uniform macroscopic and microscopic distribution, wherein the at least one of crystals and particles of tungsten carbide include at least one selected from the group consisting of irregular, oval, round nano and micro-areas filled with an alloy based on metal.

2. The cast structural element according to claim 1, wherein the at least one selected from the group consisting of irregular oval, round nano and micro-areas filled with an alloy based on metal are present within a internal part of the at least one of crystals and particles of tungsten carbide and within a external part, at walls, their structure is uniform, and the at least one of crystals and particles formed in situ in liquid alloy and are present within a matrix, wherein the matrix was formed after a alloy crystallization process.

3. The cast structural element according to claim 1, wherein a volume of at least one type of tungsten carbide within the layer comprising composite material is between 15 to 50% by volume.

4. The cast structural element according to claim 1, wherein a size of the at least one of crystals and particles of tungsten carbide within the layer comprising the composite material is between 0.5 and 30 μm.

5. The cast structural element according to claim 1, wherein within a area of the at least one of crystal and particle of tungsten carbide within the layer comprising composite materials, a size of areas filled with metal or alloy is between 0.1 to 4.5 μm.

6. The cast structural element according to claim 1, wherein the layer comprising the composite material comprises additional types of carbides or borides subject to self-propagating high-temperature synthesis reaction, TiC, MoC, NbC, ZrC, VC, TaC, TaB, TiB.sub.2 or mixes thereof, except for SiC.

7. The cast structural element according to claim 6, wherein a mixture of powders to produce the composite material comprising tungsten carbide within the structural element layer comprises at least one of tungsten and carrier powder of high tungsten content between 90-97% wt. and carbon, in the form of high purity carbon or other carrier of high carbon content or their mixes, within the range from 3 to 10% wt.

8. The cast structural element according to claim 6, wherein a mixture of powders for producing the composite material comprising tungsten carbide within the structural element layer comprises: a. tungsten powder in the form of at least one of microcrystalline, nanocrystalline powder,. and agglomerates of nanoparticles, and other carrier of high tungsten content, b. carbon powder in the form of at least one of graphite, other carrier of high carbon content, and mixtures thereof, and c. catalyst in the form of carbide reactants other than WC or boride, which are subject to self-propagating high temperature synthesis reaction, TiC, MoC, NbC, ZrC, VC, TaC, TaB, TiB.sub.2 or the mixtures thereof, except for SiC.

9. A method of producing a cast structural element including composite material based on alloys reinforced with tungsten carbide in the form of at least one of crystals and particles, a microstructure of the composite material within a layer comprises at least one of faceted crystals and faceted particles of tungsten carbide that provide uniform macroscopic and microscopic distribution, wherein the at least one of crystals and particles of tungsten carbide include at least one selected from the group consisting of irregular, oval, round nano and micro-areas filled with an alloy based on metal, the method includes the following steps: a. coating a casting mould cavity or core with reactive liquid casting coating comprising a mixture of powders: i. wherein the mixture of powders includes at least one of tungsten and carrier powder of high tungsten content between 90-97% wt. and carbon in the form of high purity carbon or other carrier of high carbon content or their mixes, within the range from 3 to 10% wt., and a carrier, or ii. wherein the mixture of powders includes a. tungsten powder in the form of at least one of microcrystalline, nanocrystalline powder, and agglomerates of nanoparticles, and other carrier of high tungsten content, b. carbon powder in the form of at least one of graphite, other carrier of high carbon content, and mixtures thereof, and c. catalyst in the form of carbide reactants other than WC or boride, which are subject to self-propagating high temperature synthesis reaction, TiC, MoC, NbC, ZrC, VC, TaC, TaB, TiB.sub.2 or the mixtures thereof, except for SiC; b. drying, c. pouring the mould cavity with an alloy wherein heat supplied by the liquid alloy in the form of high temperature provides energy necessary to initiate a in situ reaction of a ceramic phase in a form of at least one type of tungsten carbide or tungsten carbide with addition of other types of carbides that are subject to self-propagating high temperature synthesis reaction and represent a catalyst for a tungsten carbide synthesis reaction.

10. The method to claim 9, wherein the carrier is a solution of a solvent with an addition of a polymer.

11. The method according to claim 10, wherein the solvent is an ethyl alcohol.

12. The method according to claim 10, wherein the polymer is resin of low gas emission.

13. The method according to claim 9, wherein a surface density of the reactive cast coating is between 0.29 and 2 g/cm.sup.2.

14. The method according to claim 9, wherein a percentage ratio of the powders mixture to the carrier is 6:1 to 1:1.

15. The method according to claim 9, wherein before addition of powders to the cast coating carrier, the powders are dried at a temperature equal to or above 100° C.

16. The cast structural element according to claim 1, wherein a volume of at least one type of tungsten carbide within the layer comprising composite material is between 19 and 35% by volume.

17. The cast structural element according to claim 1, wherein a mixture of powders to produce the composite material comprising tungsten carbide within the structural element layer comprises tungsten powder between 93-95% wt. and carbon powder between 5-7% wt.

18. The cast structural element according to claim 1, wherein a mixture of powders to produce the composite material comprising tungsten carbide within the structural element layer comprises tungsten powder in the amount of 94% wt. and carbon in the form of graphite in the amount of ca. 6% wt.

19. The method according to claim 9, wherein the surface density of the reactive cast coating is between 0.29 and 0.6 g/cm.sup.2.

20. The method according to claim 9, wherein the percentage ratio of the powders mixture to the carrier is 4:1.

Description

EXAMPLE 1

[0045] According to one embodiment, the core 1 of the mould to produce the pump body casting is coated with the reactive coating 2 using a sprayer 3, as shown in the FIG. 1A. As a result, pump 4 body casting with the layer 5 comprising composite material (FIG. 1B) produced in situ in produced with visible morphology of wall-like tungsten carbide 6 consisting of two forms, one in the internal part of a particle comprising oval areas filled with the alloy and another in the external part of a particle deprived of areas filled with the alloy 6, as shown in the FIG. 2. Layers 5 comprising the composite material may also be form on the filter (FIG. 1C, 1D) or compressor (FIG. 1E).

[0046] To form the layer 5 of WC reinforced composite in the internal surface of the pump 4 body subject to intense wear, cores of the casting moulds 1 are prepared. The reactive cast coating 2 was applied directly on the surface of the cores 1 made of quartz sand and furan resin. The coating 2 is made by mixing tungsten powder of particle size ca. 5 μm and graphite powder of particle size ca. 5 μm. The mixture of powders was made using 96% wt. of tungsten and 4% wt. of graphite as well as 94% wt. of tungsten and 6% wt. of graphite in the first and second cast coating respectively. Then, the weighed amounts of powders were introduced into liquid solution of resin in the alcohol representing the carrier and air dried gluing agent. Mutual ratio of the tungsten and graphite powders mixture to liquid solution of gluing agent in both cases was 4:1 parts by weight. The whole was subject to mixing in order to obtain uniform reactive consistency of the cast reactive coating. The mixed reactive cast coating 2 was applied by means of a spray gun 3 on the casting core 1, representing the internal shape of the pump 4. The coating 2 was applied in layers until obtaining surface density 0.5 g/cm.sup.2 and 0.45 g/cm.sup.2 respectively for the layer number 1 and 2. Then, the cores 1 were dried followed by installation in the mould cavity, and then each of the moulds was assembled and filled with liquid alloy of temperature 1380° C. Using the aforementioned method, two bodies of the pump were made wherein each of them had the core area equal to ca. 3789 cm.sup.2. In both cases, the produced castings had cores with a microstructure characteristic for grey cast iron with separated flake graphite whose outer surface was reinforced with the composite layer 5 comprising WC particles 6. Application of the casting cores 1 of the same area and similar surface density of the applied reactive coating 2 was intended and performed in order to show the impact of the applied stoichiometry of the powders mix on the continuity of the composite layer. The results are presented in the FIGS. 7 A.1-A.3 and B.1-B.3. The observations showed that application of the powders mix of composition representing 96% wt. W to 4% wt. C allowed for obtaining the continuity of the layer at the level ca. 80%, and in case of the composition 94% wt. W to 6% wt. C specified in the patent application as designed for producing the in situ composite layer, characterized with the continuity at the level of 100%.

[0047] In both types of pumps bodies, composite layers were reinforced with tungsten carbide, using reactive casting coatings of surface density given in Table 1, in order to obtain continuity at the level between 100% and 80% of the pump internal surface. This shows that together with the increase of share of atomic tungsten in the powders mixture, the synthesis reaction deteriorates resulting in lack of continuous composite layer. Continuity of the layer at the level of 80% is acceptable in industrial application.

TABLE-US-00001 TABLE 1 Mass fraction, Surface density of Weight of Layer Core surface [% wt.] the reactive cast the applied Protective continuity No. [cm.sup.2] W C coating [g/cm.sup.2] coating [g] coating [%] 1. 3247.52 94 6 0.29 1000 not available 100 2. 3247.52 94 6 0.4 1300 not available 100 3. 3789.62 94 6 0.29 1100 not available 100 4. 3789.62 94 6 0.4 1500 not available 100 5. 3789.62 94 6 0.5 1894.5 not available 100 6. 3247.52 96 4 0.29 1000 not available 100 7. 3247.52 96 4 0.4 1300 not available 100 8. 3789.62 96 4 0.29 1100 not available 100 9. 3789.62 96 4 0.4 1500 not available 100 10. 3789.62 96 4 0.5 1894.5 not available 90 11. 3247.52 96 4 0.5 1623.76 not available 90 12. 3247.52 96 4 0.5 1623.76 applied 80 13. 3247.52 96 4 0.6 1623.76 not available 80

[0048] As a result of the synthesis reaction, local composite reinforcements reinforced with particles of a t least one tungsten carbide type, are formed in the cast steel casting. The core 2 of the casting, after the crystallization process had the microstructure characteristic for the given grade of the. alloy, however the in situ crystals 6 are formed within the casting pad area. Such a crystal 6 has a morphology consisting of two different areas. One of the areas is within the internal part of the crystal 6 of tungsten carbide and comprise micro-areas 7 of shape similar to oval, filled with an alloy based on metal, and the other one is a rim 8 surrounding it deprived of oval micro-areas filled with alloy, as showed in the FIG. 2. Average particle size preferably is within the range from 4 to 18 μm, average size of areas filled with the base alloy is from 0.05 to 0.45 μm, as showed in the FIG. 3.

[0049] The wear index—determined using the Ball-on-disk method—of the layer 5 with composite material reinforced with tungsten carbide in the pump body casting of grey cast iron with flake graphite, representing the base alloy, is from 5 to 8 * 10.sup.−6 mm.sup.3/N*m, and in the pump body of grey cast iron with flake graphite representing the base alloy without the reinforcement layer is 37.6 * 10.sup.−6 mm.sup.3/N*m. I.e. the layer with the composite material according to the invention wear from 4.7 to 7.5 times less comparing to the pomp made of grey cast iron.

EXAMPLE 2

[0050] In order to produce the in situ composite layer 5 reinforced with WC, the core based on sand and resin was prepared, representing an element of the casting mould 1 based on quartz sand and water glass blown with CO.sub.2. The casting mould 1 cavity was coated with reactive cast coating 2. The coating 2 is made by mixing tungsten powder of particle size 5 μm and graphite powder of particle size ca. 5 μm. The mixture of the powders was made using 94% wt. of tungsten and 6% wt. of graphite. Then, the powders were introduced into liquid solution of colophony in the alcohol representing the carrier and air dried gluing agent. Mutual ratio of the tungsten and graphite powders mixture to liquid gluing agent was 4:1 parts by weight. The whole was subject to mixing in order to obtain uniform reactive consistency of the cast reactive coating. The mixed reactive casting coating 2 was applied by spraying with a spray gun 3. The coating 2 was applied in layers until obtaining surface density 0.29 g/cm.sup.2 or 0.4 g/cm.sup.2. Then, the casting mould cavity was baked in order to remove residues of alcohol and moisture follow by filling with liquid alloy at temperature ca. 1400° C. The casting, after the crystallization process had the microstructure of grey cast iron with flake graphite, however within the area of composite layer, the in situ crystals 6 and/or WC particles were formed, having a structure formed of two different areas. One of the areas is within the internal part of the crystal 6 or WC particle and comprises micro-areas 7 of shape similar to oval, filled with an alloy based on metal, and the other one is a rim 8 surrounding it deprived of oval micro-areas filled with alloy. The cross-section of the layer with the selected magnified areas is presented in the FIG. 4. In order to assess the share of the reinforcing phase, one determined surface area content of phases identified within microstructure, i.e. flake graphite and base alloy representing the matrix of the composite layer and tungsten carbide representing the reinforcement phase. Exemplary microstructures with determined surface area content and the obtained results are presented in the FIG. 5. Surface share of tungsten carbides in this case is 25% and of the matrix 70%, the rest is graphite being the component of the basic alloy used to produce the cast. Moreover, average tungsten carbide particle size was estimated and it was determined as an average of two measurements of diagonals intersected at the right angle. The results show to bimodal size distribution of tungsten carbide within the composite layer that achieves the first distribution maximum for the distribution from 0.5 to 6 μm, and the other from 7 to 30 μm. The results are presented in the form of a histogram, as showed in the FIG. 6.

EXAMPLE 3

[0051] In order to produce internal layer of the pump body that is subject to intense wear, the layers 5 comprising the composite material reinforced with ceramic phases particles, such as tungsten and titanium carbides, the casting mould core 1 is prepared. The reactive casting coating 2 is applied directly on the surface of the core 1 made of quartz sand and water glass and blown with CO.sub.2. The coating 2 was made based on mixing 80% wt. of reaction substrates forming tungsten carbide and 20% wt. of reaction substrates forming titanium carbide. The mixture of powders of reaction substrates forming tungsten carbide was made in the weight ratio W:C equal to 94:6% wt. Reaction substrates forming TiC were prepared in atomic ratio 55% Ti : 45% C. In this case, the following powders were used: tungsten of micro-crystalline morphology and particle size ca. 4.5 μm, titanium of spongy morphology of particle size 44 μm and graphite of particle size below 5 μm. The prepared mixture of powders was introduced into liquid solution of colophony resin in ethyl alcohol representing the carrier and air dried gluing agent. Mutual ratio of the tungsten and graphite powders to liquid gluing agent was 4:1 parts by weight. The cast coating was prepared based on 600 g of powders mixture and 150 g of solution. The whole was subject to mixing in order to obtain uniform reactive consistency of the cast reactive coating 2. The mixed reactive cast coating 2 was applied by spraying with a spray gun 3. Then, the core 1 together with the applied reactive cast coating 2 was dried at temperature above 100° C. in order to remove residues of alcohol and moisture. The core 1 was installed inside the casting mould cavity, and then the mould was assembled and filled with liquid alloy. The casting 4, after the crystallization process had the microstructure of grey cast iron with flake graphite, however within the composite layer 5 area, the in situ particles of tungsten and titanium carbides were formed (FIG. 8). The obtained microstructure were used to determine the surface area content of individual phases representing microstructure of the produced in situ composite layer. The results are showed in the FIG. 9 considering the division of phases present within the area of the matrix and composite layer. The presence of irregular area of non-faceted particles of TiC within the microstructure indicates the addition of percentage share of pure TiC formation reaction substrates. Hardness test performed using Vickers method (HV1) under the load of 1 kG i.e. 9.81 N within the area of the base alloy and the composite layer showed the values at the level of 312.3 HV1 and 767.1 HV1 respectively. The obtained results indicate over twice increase of hardness of the top layer of the cast made together with the in situ composite layer.