TWI494290B - Method for manufacturing carbide cermet powder - Google Patents

Description

Method for manufacturing carbide porcelain gold powder

This invention relates to a porcelain gold powder, and more particularly to a method of making a carbide china gold powder.

In the steelmaking process, steel mills usually use a processing roll to transport the steel strip on the Cold-rolling Annealing (CAL) and the Continuous Galvanizing Line (CGL). Generally speaking, a CGL production line must be equipped with four different rollers such as a normal temperature roller, a medium temperature furnace roller, a high temperature furnace roller and a zinc groove roller. The surfaces of these four rollers must be coated with a porcelain gold coating to achieve wear resistance, high temperature oxidation and corrosion resistance.

Early room temperature process rolls were typically plated with hard chrome rolls. Later, in order to extend the service life of the process rolls and reduce environmental pollution, they were gradually replaced by thermal sprayed normal temperature rolls. When a normal temperature process roll is produced, a porcelain gold powder is generally used as a spray material. The following are the manufacturing techniques for several types of porcelain gold coatings.

U.S. Patent No. 3,071,489 discloses a coating material and a method of manufacturing the same. This coating material contained 70% by weight of tungsten carbide (WC), 24% by weight of chromium carbide (Cr ₃ C ₂ ) and 6% by weight of nickel (Ni). The coating material is superior to the conventional tungsten carbide-cobalt (WC-Co) coating material in its resistance to atmospheric corrosion, corrosion resistance to micro-alkaline aqueous solutions, and high temperature resistance (> 534 ° C (1000 ° F)).

In addition, the patented technology in the manufacture of the spray coating is to sintering and crushing the raw materials such as tungsten, chrome-nickel alloy and carbon; or the raw material tungsten, chrome-nickel alloy and carbon are mixed and sintered. In the manner of pulverization, a porcelain gold powder containing 70% by weight of WC-24% by weight of Cr ₃ C ₂ -6 wt% of Ni was prepared. The porcelain gold powder is then sprayed with a spray gun (D-Gun) to form a coating. The temperature of the spray flame of the spray gun is as high as 3000 ° C. The injection method of the porcelain gold powder is simple, the particle size range and the flow performance are required to be low, and the powder flow rate can reach 760 m/s. However, this patented technology does not disclose any relationship between the preparation of WC-Cr ₃ C ₂ -Ni porcelain gold powder by the granulation sintering method, and the obtained porcelain gold powder and the deposition efficiency (DE) of the coating. In addition, the spray equipment is not sold externally and the equipment is not easily available.

In view of this, two widely used thermal spray systems, plasma spray and high-speed oxygen flame spray (HVOF), have been developed. Among them, the plasma melting system flame temperature can reach 10000 ° C, and the high-speed oxygen flame spraying system flame temperature can reach 2300 ° C. Carbide porcelain gold powder is usually sprayed using an HVOF spray system to avoid excessive temperature and decomposition or oxidation of carbides. However, since the HVOF spray system requires good fluidity during powder injection and nitrogen transport, and the flame temperature is low, the particle size distribution range is narrow and thin. Therefore, the carbide porcelain gold powder produced by the sintering and pulverization method or the fusion and pulverization method is not suitable for the HVOF spray system, and the porcelain gold powder produced by the granulation and sintering method must be used.

LMBerger et al., in the September 2008 issue of Thermal Spray Technology, Vol. 17, No. 3, pp. 395-403, discloses the use of WC, Cr ₃ C ₂ and Ni as raw materials, and by sintering. Porcelain gold powder is prepared by two methods such as sintering and crushing and agglomeration and sintering. Then compare the crystal phase, composition and hardness of the coating obtained by spraying the porcelain gold powder prepared by the two methods through a high-speed oxygen flame (HVOF) spray system.

The powder obtained after granulation and sintering may or may not contain (W,Cr) ₂ C, but the composition of the coating formed by the spray coating contains the (W,Cr) ₂ C phase. Such results show that in the process of manufacturing WC-Cr ₃ C ₂ -Ni porcelain gold powder, WC and Cr ₃ C ₂ may undergo a sintering reaction, and in the HVOF spraying process, a sintering reaction is necessary to form (W,Cr) _{2 .} C. Secondly, the WC-Cr ₃ C ₂ -Ni spray coating has better resistance to high temperature oxidation at 200 ° C ~ 800 ° C than the WC - 10 Co-4Cr coating.

In addition, WC-Cr ₃ C ₂ -Ni porcelain gold powder was sprayed using different spray systems, and the resulting coatings had different hardnesses. Sprayed by the model JP-5000 supplied by Praxair Surface Technologies and the K2 HVOF system supplied by GTV of Germany, and the hardness of the coating obtained is Hv0.3 (300g load). =970. On the other hand, the coating hardness obtained by D-Gun sputtering was Hv0.3=1250. This result is due to the fact that when the D-gun is used for the coating, the flame temperature is higher, so that the (W,Cr) ₂ C in the resulting coating is relatively more. Such results also show that properties such as coating hardness are no longer related only to the grain characteristics of WC single particles.

However, this technique only mentions that the coating stacking efficiency of WC-Cr ₃ C ₂ -Ni porcelain gold powder is better than WC-CoCr porcelain gold powder, but does not explain the coating formed by WC-Cr ₃ C ₂ -Ni porcelain gold powder. The stacking efficiency is superior and the manufacturing parameters of the coating are not stated.

US Patent Publication No. 20010019742 A1 discloses a formulation composition and a manufacturing method of a high-toughness WC-Cr ₃ C ₂ -Ni(NiCr) granulated and sintered powder, wherein the powder composition comprises 70 wt% of WC and 15 wt% of Cr. ₃ C ₂ and 15 wt% of NiCr. This patented technology uses 5μm~20μm WC, 1μm~10μm chromium carbide (Cr ₃ C ₂ , Cr ₇ C ₃ , Cr ₂₃ C ₆ ), and 1μm~15μm Ni or Ni alloy powder as raw materials, and is 75wt%. ~79wt% carbide (WC, chromium carbide) and 5wt%~25wt% metal (Ni, Ni alloy) to prepare porcelain gold powder.

In the production, the raw materials of the powder are mixed, and then water and a binder polyvinyl alcohol (PVA) are added to make a slurry. Next, granulation is carried out by a spray dryer, and sintering is carried out in a vacuum or an atmosphere of argon (Ar) at a temperature of 1200 ° C to 1400 ° C, followed by pulverization and sieving to obtain granulation of 6 μm to 63 μm. And sintered porcelain powder for carbide spraying. Then, after being sprayed with, for example, HVOF of JP-5000, a coating having high coating deposition ratio, high toughness, and high impact resistance can be obtained.

Further, the particle diameter of 70 wt% of WC-15 wt% Cr ₃ C2-15 wt% NiCr ranges from 15 μm to 45 μm. Further, a powder having a WC particle diameter of 11 μm, a Cr ₃ C ₂ particle diameter of 5 μm, and a NiCr alloy powder particle diameter of 5 μm was selected, and after granulating and sintering the porcelain gold powder, the deposition ratio of the coating layer after the melt deposition was selected. 42%, hardness HV0.2=1200, and no crack under high load. When a carbide material having a fine particle diameter is used, for example, when the WC particle diameter is 2 μm and the Cr ₃ C ₂ particle diameter is 0.8 μm, the deposition ratio of the coating layer after the melt deposition is 46%, and the hardness HV0.2 = 1250, however, there will be cracks under high load. On the other hand, when a carbide raw material having a relatively large particle diameter is used, for example, when the WC particle diameter is 20 μm and the Cr ₃ C ₂ particle diameter is 10 μm, the deposition ratio of the coating layer after the melt deposition is 30%, and the hardness HV0. .2=900, and there is no crack under high load. However, the technique of this patent does not investigate the fabrication of coatings with high stacking rates.

U.S. Patent No. 4,912,835 discloses an HVOF using 88 wt% WC-12 wt% Co and 73 wt% WC-20 wt% Cr-7 wt% Ni coating material using an oxygen-hydrocarbon gas as a heating source. The thermal spray method is used to manufacture roll coatings for rolled aluminum and rolled copper alloys. This patented technique controls the porosity of the coating to less than 1.8% and controls the maximum roughness ( _Rmax ) of the coating surface to less than 3 [mu]m. In this way, the roller having the coating on the surface can replace the chromium plating roller. When the temperature is above 300 °C, the rolling performance of the coated roller is much better than that of the chrome roller, and the hardness under long-term use (Hv=1100~1200) is unchanged. In addition, the rolled aluminum sheet does not cause scratches and indents, and the hardness of the chrome-plated coating is reduced from 850 to 360 after rolling, and aluminum is attached to the chrome-plated coating. However, this patented technique does not teach which of the particle size characteristics of the carbide porcelain powder can produce a coating having a porosity of less than 1.8% and a surface roughness of less than 3 μm, and there is no discussion of the coating stacking rate.

U.S. Patent Publication No. 6071324 proposes the development of a WC-Co-Cr porcelain powder material having excellent wear resistance. The granulated and sintered porcelain gold powder of WC-Co-Cr is mixed with 5 wt% to 35 wt% Co alloy powder. The coating produced by HVOF or D-Gun spray has excellent erosion and wear resistance. It is used in gas or oil high pressure gate valves (Gate valve) and aircraft landing gears (Landing gear). This patented technology does not have a discussion of coating stacking rates.

U.S. Patent Publication No. 20060053967 A1 proposes the development of a WC-Co-Cr porcelain powder material having excellent wear resistance. This patented technology granulates and sinters WC-Cr and WC-Co-Cr into porcelain gold powder. Wherein, the Co content may be 5 wt% to 20 wt%, the Cr content may be 1 wt% to 10 wt%, and the selected particle diameter ranges from 2 μm to 50 μm, the WC particle diameter is 3 μm to 9 μm (more preferably 5 μm to 7 μm), and the particle strength is 400 Mpa. ~900Mpa (600MPa~700MPa is better). The coating obtained by HVOF spraying has excellent cavitation erosion resistance. This patented technology does not have a discussion of coating stacking rates.

Y. Ishikawa et al., pp. 384-390 of the Journal of Thermal Spray Technology, Vol. 14, No. 3, published in September 2004, states that electroplated hard chrome rolls are commonly used for corrosion and wear resistance, but hexavalent chromium in electroplating baths. It is harmful to the environment and the human body, so the high-speed oxygen flame HVOF spray porcelain gold coating is used instead of the chrome plating layer. HVOF can make the spray particle speed more than 500m / s, the temperature can reach 2000 ° C, and the particles in the semi-molten state can be flattened to form a long strip and then deposited into a coating.

Further, the granulated and sintered WC-20wt% Cr ₃ C ₂ -7wt% Ni porcelain gold powder has a particle diameter of 15 μm to 53 μm, and a ratio of less than 45 μm accounts for 55%, and a bulk density [ie, bulk density (BD)] is 3.99. g/cm ³ . The modified HVOF (GS-HVOF) with a gas hood (Gas-shoud) is added to the front end of the flame to reduce the oxidation of the semi-molten powder particles, for example, WC is oxidized to W ₂ C to ensure the coating. Corrosion resistance and wear resistance. The GS-HVOF system increases the rate of spray particles to at least 50 m/s and can reach >770 m/s and has a coating hardness of Hv0.3 > 1250. The greater the hardness, the less the wear measured by the suga-type abrasion tester.

The content presented in this paper only shows the powder characteristics of commercial WC-20wt%Cr ₃ C ₂ -7wt%Ni porcelain gold powder, and the improved GS-HVOF spray system can reduce the W ₂ C phase, but there is no WC Discussion on the deposition efficiency of -Cr3C2-Ni porcelain gold powder.

Y. Ishikawa et al., September 2007, Surface & Coatings Technology, Vol. 201, No. 4718-4727, discloses a pin-on-disk wear tester. The abrasion resistance of the HVOF and GS-HVOF sprayed WC-20 wt% Cr ₃ C ₂ -7 wt% Ni coating was measured. The results show that the wear resistance of the HVOF spray coating is about 3 times that of the chrome plating layer. This is because the coating has W ₂ C and Cr ₂ O ₃ (oxidized by Cr ₃ C ₂ ), but GS-HVOF The wear resistance of the spray coating is the same as that of the chrome plating. In addition, after the oxidative heat treatment of the WC-20wt%Cr ₃ C ₂ -7wt% Ni coating, Cr ₂ O ₃ , WO ₃ , NiO and NiWO ₄ can be formed to increase the sliding wear resistance of the coating. However, this paper only discusses the effect of HVOF and GS-HVOF spray parameters on the sliding wear resistance of WC-20wt%Cr ₃ C ₂ -7wt%Ni coating, but does not discuss the influence of the melting parameters on the coating stacking efficiency.

W. Fang et al., Journal of Materials Processing Technology, Vol. 209, pp. 3561-3567, published in 2009, discloses operating conditions such as H ₂ , O ₂ and powder flow rates of HVOF, The flow rate of _{2 has} the greatest influence on the hardness and porosity of WC-CrC-Ni porcelain gold coating. Further, a granulated and sintered WC-CrC-Ni porcelain gold powder having a particle diameter of 10 μm to 60 μm can obtain a coating having an Hv0.2=1150±50 and a porosity of 1.2±0.2% under the optimum HVOF conditions. The resulting coating has better wear resistance at 25 ° C and 450 ° C than chromium plating. However, this paper focuses on the effect of HVOF operating conditions on the hardness and wear resistance of the granulated and sintered WC-Cr ₃ C ₂ -Ni porcelain gold powder spray coating, and does not discuss the effect on the coating stacking rate.

C.-J. Li et al., in the September 2007 issue of Materials Science and Technology (Materials Science and Technology), Vol. 20, No. 9, pp. 1087-1096, states that HVOF (flame temperature up to 2300 ° C) The formation of the spray coating is obtained by solidification of the solid-liquid two-phase droplets to the impact surface after high-speed deposition. The droplets formed by the larger carbide particles may be caused by large kinetic energy and less melting during the impact process. It is easy to rebound and therefore not easily retained in the coating.

However, the WC-12Co or WC-17Co porcelain powder discussed in this paper is composed of only a single-phase high melting point (Tm=2870°C) carbide WC and a low-temperature fusible bonding metal Co (Tm=1495°C). . In addition, the method for manufacturing the porcelain gold powder contained in the present invention is a post-sinter pulverization, a cluster re-agglomeration obtained by sintering WC and Co first, and a WC electroplated coated cobalt (Clad Co).

The Republic of China Patent Publication No. 200831708 discloses a powder using WC-12 wt% Co, WC-20 wt% Cr ₃ C ₂ -7 wt% Ni or WC-10 wt% Co-4 wt% Cr, and controlling the particle size of the granulated and sintered powder. The ratio of more than 25 μm is 0.5% to 15%, and the ratio of particle diameter is less than 10 μm is 0.5% to 15%, and the bulk density is more than 3.6 g/cm ³ , the particle strength is 150 MPa to 800 MPa, and the roughness Ra of the coating surface is smaller than 3 μm. However, this patent only mentions that the bulk density of WC-12wt% Co porcelain powder is less than 6g/cm ³ , the WC primary particle diameter is less than 6μm, and the particle strength is less than 700Mpa, which can improve the deposition rate, which is a qualitative description.

The Republic of China Patent Publication No. 201127994 A discloses a metal containing ruthenium carbide or chromium carbide, and 5 wt% to 40 wt% of ruthenium-containing metal (main composition: Si = 0.1 wt% to 10 wt%, Ni = 5 wt% to 20 wt%, Cr=0.5wt%~20wt%, the rest is Fe, and may contain additive elements such as Al, Mo and Mn) as granulated and sintered porcelain gold powder of the bonding metal, instead of the traditional porcelain gold powder with Co as the bonding metal. When the particle size of the granulated and sintered porcelain gold powder is at least 8 μm to 15 μm, no splitting occurs. The average particle size of the granulated and sintered porcelain gold powder is preferably 30 μm, at which time the melt coating has increased tightness, and the hardness and wear resistance are improved. In addition, regardless of the particle size, the particle strength is greater than 150 MPa to 200 MPa, no slag is generated, and when the particle strength is less than 700 MPa, the coating deposition efficiency of the spray powder can be improved. However, this patent only mentions the effect of the upper limit of the particle strength (700 MPa) of the granulated and sintered WC-Cr ₃ C ₂ -(FeSiNiCr) porcelain powder on the coating deposition rate, but does not discuss the process factor to the coating deposition rate. The impact.

The Republic of China Patent Publication No. 200916603 A discloses a granulated and sintered porcelain gold powder comprising 65 wt% to 70 wt% of CoNiCrAlY, 30 wt% to 50 wt% of Cr ₃ C ₂ , and less than 20 wt% of Y ₂ O ₃ . 20μm~60μm. The coating formed by the spray has excellent anti-manganese scaling properties, and has wear resistance and thermal shock resistance, and is suitable for 900 ° C high temperature furnace rolls. When the particle size of the porcelain gold powder is 20 μm to 60 μm, the coating density can be balanced and splashing can be avoided. When the strength of the porcelain gold powder is 10 MPa or more, no splashing will occur. The coating deposition rate is better than 35%, 30~35% is acceptable, and less than 30% is bad. However, this patent does not investigate the effect of the characteristics of CoNiCrAlY-Cr ₃ C ₂ -Y ₂ O ₃ granulated and sintered porcelain powder powder on the coating deposition rate.

At present, when granulated and sintered 73 wt% WC-20 wt% Cr ₃ C ₂ -7 wt% Ni porcelain gold powder is used for HVOF spray spraying, 60 wt% to 70 wt% of the powder cannot be effectively deposited on the surface of the roller to form a coating. As a result, the manufacturing cost of the coated roller increases, and it is impossible to compete with the chrome roll. In view of this, in order to reduce the amount of powder for obtaining the target thickness coating, and to take into consideration the hardness, porosity, and abrasion resistance of the coating, it is possible to improve the deposition efficiency of the coating.

In general, in addition to the appropriate HVOF melting parameters, the method of increasing the stacking efficiency starts with the porcelain gold powder manufacturing technology. Regarding the manufacturing technology of porcelain gold powder, only a few documents or patents qualitatively describe some powder characteristics, such as WC primary particle diameter less than 6μm, bulk density less than 6g/cm ³ , particle strength less than a certain value, etc., and the target values of these characteristics It will vary with the composition of the recipe. For example, when WC-Cr ₃ C ₂ -(FeSiNiCr) porcelain gold powder and WC-12Co have a particle strength of less than 700 MPa, the stacking efficiency can be improved. However, for 73 wt% WC-20 wt% Cr ₃ C ₂ -7 wt% Ni porcelain gold powder, the particle strength is allowed to be 400 MPa, and for Cr ₃ C ₂ + CoNiCrAlY, the particle strength is set to 10 MPa. Strictly speaking, the evaluation of particle strength is not an overall powder property, and it is easy to vary depending on individual particle size and shape.

Therefore, an object of the present invention is to provide a method for manufacturing a carbide porcelain gold powder, which can improve the coating deposition rate, and can greatly reduce the amount of porcelain gold powder required for each roller of high-speed oxygen flame spray coating, and further Reduce the cost of roller production.

According to the above object of the present invention, a method for producing a carbide porcelain gold powder is provided, which comprises the following steps. Provide raw materials. The raw material comprises a plurality of tungsten carbide powders having a content of 73% by weight, a plurality of chromium carbide powders having a content of 20% by weight, and a plurality of nickel powders having a content of 7% by weight. The raw material is subjected to a mixed grinding treatment to obtain a mixed abrasive. Wherein, the mixed abrasive has an intermediate particle diameter (D50) of less than or equal to 6.7 μm. A granulation treatment is carried out on the mixed mill to obtain a plurality of carbide particles. These carbide particles are subjected to a sintering treatment to obtain a plurality of carbide porcelain gold powders.

According to an embodiment of the present invention, each of the tungsten carbide powders has a Fisher sub-sieve size (Fss) of 1.5 μm to 2.5 μm.

According to another embodiment of the present invention, the above-mentioned carbide porcelain gold powder has an average particle diameter (Dmean) of from 15 μm to 45 μm.

According to still another embodiment of the present invention, the mixed abrasive has an intermediate particle diameter of less than or equal to 5.5 μm.

According to still another embodiment of the present invention, the above-mentioned carbide porcelain gold powder has a bulk density of less than or equal to 3.81 g/cm ³ .

According to still another embodiment of the present invention, the snow particle size of each of the tungsten carbide powders described above is 1.5 μm, and the intermediate particle diameter of the tungsten carbide powders is less than or equal to 3.5 μm. The intermediate particle diameter of the chromium carbide powder was 3.8 μm. The intermediate particle diameter of the nickel powder was 12.4 μm. The intermediate particle size of the mixed abrasive is less than or equal to 5.5 μm. The bulk density of the carbide porcelain gold powder is less than or equal to 3.80 g/cm ³ .

According to still another embodiment of the present invention, the snow particle size of each of the tungsten carbide powders described above is from 2.0 μm to 2.5 μm, and the intermediate particle diameter of the tungsten carbide powders is less than or equal to 5.4 μm. The intermediate particle diameter of the chromium carbide powder was 3.8 μm. The intermediate particle diameter of the nickel powder was 12.4 μm. The intermediate particle size of the mixed abrasive is less than or equal to 5.5 μm. The bulk density of the carbide porcelain gold powder is less than or equal to 3.75 g/cm ³ .

According to still another embodiment of the present invention, the temperature of the sintering treatment is 1200 ° C to 1400 ° C.

100‧‧‧ method

102‧‧‧Steps

104‧‧‧Steps

106‧‧‧Steps

108‧‧‧Steps

The above and other objects, features, advantages and embodiments of the present invention will become more <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; A flow chart of the manufacturing method.

The invention provides a method for producing a carbide with good wear resistance, namely WC-Cr ₃ C ₂ -Ni, porcelain gold powder. WC-Cr ₃ C ₂ -Ni is a porcelain gold powder composed of two kinds of carbides and a bonding metal Ni (melting temperature Tm=1453°C), wherein two kinds of carbides are between WC and Cr ₃ C ₂ (Tm=1895°C). Mutual melting [e.g., formation of a (W, Cr) ₂ C] phase, the packing effect for solid-liquid droplets is different from the WC of a single phase.

Most of the previously developed WC-Cr ₃ C ₂ -Ni porcelain gold powders were prepared by melt pulverization or sintering pulverization, and sprayed with D-Gun spray with high flame temperature (~3000 ° C). However, since only high-speed oxygen flame spray guns are currently available on the market, the temperature is low (~2300 ° C), and there are strict requirements on the fluidity and fusibility of the porcelain gold powder. Therefore, the present invention employs a method of producing granulated and sintered WC-Cr ₃ C ₂ -Ni porcelain gold powder to improve the stacking efficiency of the HVOF spray coating.

Please refer to FIG. 1 , which is a flow chart showing a method for manufacturing a carbide porcelain gold powder according to an embodiment of the present invention. When the carbide china gold powder is prepared, the raw materials can be provided as described in step 102 of method 100. In this embodiment, the composition of the carbide porcelain gold powder may be, for example, 73 wt% WC-20 wt% Cr ₃ C ₂ -7 wt% Ni, so the raw material contains some WC powder having a content of 73 wt%, and some Cr ₃ C having a content of 20 wt%. ₂ powder, and some nickel powder in an amount of 7 wt%.

In an embodiment, the particle size of the snow particles of each of the tungsten carbide powder may be, for example, 1.5 μm to 2.5 μm. In an exemplary embodiment, the snow particle size of each tungsten carbide powder is 1.5 μm, the intermediate particle diameter of the tungsten carbide powder is less than or equal to 3.5 μm, and the intermediate particle diameter of the chromium carbide powder is 3.8 μm. The diameter is 12.4 μm. In another exemplary embodiment, the snow particle size of each tungsten carbide powder is from 2.0 μm to 2.5 μm, the intermediate particle diameter of the tungsten carbide powder is less than or equal to 5.4 μm, and the intermediate particle diameter of the chromium carbide powder is 3.8 μm. The intermediate particle diameter of the nickel powder was 12.4 μm. In still another exemplary embodiment, the snow particle size of each of the tungsten carbide powders is from 2.0 μm to 2.5 μm, the intermediate particle diameter of the tungsten carbide powder is less than or equal to 5.4 μm, and the intermediate particle diameter of the chromium carbide powder is 3.8 μm, and The intermediate particle diameter of the nickel powder was 12.4 μm.

Next, as described in step 104, a raw material such as WC powder, Cr ₃ C ₂ powder, and nickel powder is stirred and mixed for a while using, for example, an Attritor, and ground to obtain a mixed abrasive. In one embodiment, the intermediate particle size of the mixed millbase can be controlled, for example, to less than or equal to 6.7 [mu]m. In a preferred embodiment, the intermediate particle size of the mixed abrasive can be controlled to be less than or equal to 5.5 μm.

Next, as described in step 106, water and a binder, such as polyvinyl alcohol, may be added to the mixed millbase and the mixed millbase is slurried. The slurry mixed abrasive is granulated by, for example, a spray dryer to obtain a plurality of carbide particles. Then, as described in step 108, these carbide particles are subjected to a sintering treatment in, for example, a vacuum or a reducing atmosphere. In one embodiment, the temperature of the sintering process can be controlled between 1200 ° C and 1400 ° C. After the carbide particles are sintered, they are then pulverized and sieved to obtain a plurality of carbide porcelain gold powders. These carbide porcelain gold powders are suitable for use in high speed oxygen flame spray systems.

In one embodiment, the average particle diameter of these carbide porcelain gold powders may be, for example, 15 μm to 45 μm. Further, the bulk density of these carbide porcelain gold powders may be, for example, less than or equal to 3.81 g/cm ³ . In an exemplary embodiment, the bulk density of the carbide china gold powder is less than or equal to 3.80 g/cm ³ . In another exemplary embodiment, the bulk density of the carbide china gold powder is less than or equal to 3.75 g/cm ³ .

In the present embodiment, a carbide porcelain gold powder applicable to an HVOF spray system is formed by controlling the particle diameter of the raw material, the particle size of the agitating and grinding mixture, and/or the bulk density of the granulated and granulated powder. In an exemplary example, these carbide porcelain gold powders are formed by spraying through an HVOF spray system. The deposition rate of the coating may be greater than 40%, and the hardness Hv0.3 of the coating may be greater than 1000, and the porosity of the coating may be less than 1%.

Hereinafter, the technical contents and effects of the present embodiment will be more specifically described using a plurality of embodiments and comparative examples, wherein numbers 1 and 4 are comparative examples, and numbers 2, 3, and 5 to 10 are examples.

In the following examples, three different particle size WC powder raw materials were selected, one with Cr ₃ C ₂ and one Ni powder. These materials were mixed for a while using a stirring mill to obtain a WC-Cr ₃ C ₂ -Ni mixed abrasive. After analyzing the particle size of the obtained WC-Cr ₃ C ₂ -Ni mixed abrasive, water and a binder were added, and the mixed abrasive was slurried. The WC-Cr ₃ C ₂ -Ni mixed abrasive was further formed into particles by a spray dryer. Thereafter, sintering is carried out in a vacuum or a reducing atmosphere at a temperature of 1200 ° C to 1400 ° C. After pulverization and sieving, 73 wt% WC-20 wt% Cr ₃ C ₂ -7 wt% Ni carbide porcelain gold powder obtained by granulation and sintering can be obtained.

A carbide powder having a particle size distribution of 15 μm to 45 μm is selected by a sieve. The bulk density and flow rate of the carbide porcelain gold powder were measured by a Hall flow meter. The ratio of the powder having a particle diameter of less than 38 μm was confirmed with a 400 mesh screen. The coating of the porcelain gold powder by HVOF spraying is based on the target coating thickness of 200 μm. After calculating the thickness of the spray coating, the amount of the carbide porcelain powder and the coating weight are calculated, and then the coating deposition efficiency is calculated.

Further, in these examples and comparative examples, the HVOF spray system employed was a sprayer of the model WokaJet 440 supplied by SULZER METCO, Switzerland. The spraying conditions are: oxygen flow rate 2050 cubic feet per minute (scfh), kerosene flow rate of 5.2 gallons per hour (gph), thermal spray distance of 300 mm, thermal spray barrel length of 152.4 mm, and powder supply of 40 g/min.

In addition, raw material powders such as WC, Cr ₃ C ₂ and Ni, mixed abrasives, and carbide porcelain powders are all obtained by the laser diffraction particle size analyzer Mastersizer 2000 provided by Malvern Instruments. The average particle size and the intermediate particle size analysis were carried out by diffracting and scattering. In addition, after the obtained porcelain gold coating was observed by an electron microscope and photographed, the ratio of the area occupied by the black holes was calculated by the image processing software to obtain porosity. The hardness of the coating was measured by the HXT-70 Vickers hardness tester provided by Shimadzu Co., Ltd., using a diamond pyramid indenter under a load of 300 g for 15 seconds. Hardness Hv0.3.

Table 1 below lists the relationship between the process conditions of these examples and the comparative examples and the characteristics of the HVOF spray coating.

The three columns of the above table show the three WC particle sizes. Commercially available WC powders typically express their particle size in Fss. Under the influence of the process factors of the carbides WC and Cr ₃ C ₂ , the carbides exhibit the phenomenon that the primary particles and the primary particles are aggregated into hard secondary particles. Further, the Ni powder produced by the hydrocarbon method also has a phenomenon in which primary particles agglomerate. The difference in binding force between the primary particles determines whether the secondary particles are easily dissolved or dispersed. The raw material which is not easily disintegrated can be analyzed and expressed by a Fisher sub-sieve sizer. The analytical measurement technique measures the porosity between the particles in the compacted powder, and then estimates the particle size of the corresponding particles. The particle size obtained is relatively close to the particle size of the primary particles.

In these examples and comparative examples, three kinds of WC powders having commercially available Fss particle diameters of 2.5 μm, 2.0 μm and 1.5 μm were used as raw materials, and then mixed with Cr ₃ C ₂ powder and Ni powder raw materials to prepare porcelain gold powder. WC powders having a Fss particle size of 2.5 μm, 2.0 μm, and 1.5 μm generally have a primary particle diameter of between 2.0 μm and 3.0 μm, between 1.5 μm and 2.5 μm, and between 1.0 μm and 2.0 μm. Observation by an electron microscope revealed that the primary particles attached to the hard aggregated particles (secondary particles) were found to be micron or submicron particles. However, the particle size of the WC powder was measured by laser diffraction and scattering, and the measured particle size was mainly the particle diameter of the secondary particle. It can be seen from Table 1 that the average particle diameters of WC powders with Fss particle size of 2.5 μm, 2.0 μm and 1.5 μm are 7.32 μm, 7.72 μm and 5.70 μm, respectively, and the corresponding intermediate particle diameters are 5.32 μm, 5.38 μm and 3.30, respectively. Mm. Although the primary particles having a Fss particle diameter of 2.0 μm are small, since the secondary particles exhibit a bimodal distribution, the average particle diameter and the intermediate particle diameter are relatively large.

A powder raw material such as 73 wt% WC, 20 wt% Cr ₃ C ₂ and 7 wt% Ni was mixed and ground by a stirring mill. The Cr ₃ C ₂ powder had an average particle diameter of 4.4 μm and an intermediate particle diameter of 3.8 μm, and the Ni powder had an average particle diameter of 14.9 μm and an intermediate particle diameter of 12.4 μm. Further, the primary particles of the Ni powder produced by the hydrocarbon method are submicron particle diameters, and are easily agglomerated, but are also easily dissolved in a stirring mill. The powders of No. 1, 2 and 3 listed in Table 1 above are three kinds of WC powders with Fss particle size of 2.5μm, 2.0μm and 1.5μm, respectively, with Cr ₃ C ₂ powder and Ni powder, and the same ratio is ground and mixed 1 73 wt% WC-20 wt% Cr ₃ C ₂ -7 wt% Ni porcelain gold powder obtained in an hour. The intermediate particle diameters of the three mixed ground porcelain gold powders obtained were 7.2 μm, 6.7 μm and 5.5 μm, respectively. Water and a binder are added to the three mixed ground porcelain gold powders, mixed at a solid concentration of 60 wt% to 75 wt%, and formulated into a slurry. After granulation by a spray dryer, sintering was carried out for 2 hours at a temperature of 1300 ° C to 1350 ° C in nitrogen. These granulated and sintered powders were appropriately dissociated, and a powder having a particle diameter of 15 μm to 45 μm was sieved for HVOF spray coating.

The granulated and sintered 73 wt% WC-20 wt% Cr ₃ C ₂ -7 wt% Ni porcelain gold powders of Nos. 1, 2 and 3 had bulk densities of 3.61 g/cm ³ , 3.39 g/cm ³ and 3.81 g/cm ^{3 , respectively} . Although the intermediate particle size of the mixed abrasive powder prepared by WC powder with Fss particle size of 2.5μm, 2.0μm and 1.5μm is sequentially decreased, the reactivity should be gradually increased, so that the particle density after sintering is sequential. Should be gradually increased. However, since the powder having a Fss particle diameter of 2.0 μm exhibits a bimodal distribution, the reactivity of the powder is low, and the coarser hard particles are relatively large, and thus the reaction activity of the hard particles is relatively relative after being crushed by stirring and grinding. Lower. Further, in the powder of No. 2, since the Cr ₃ C ₂ powder and the WC powder have undergone a diffusion reaction during the sintering process, the composition of the W element contained in the Cr ₃ C ₂ particles can be observed under an electron microscope, and part of Particles of (W,Cr) ₂ C are formed. The reaction of components such as WC and Cr ₃ C ₂ with Ni is not related to the reaction temperature because the sintering temperature has not reached the melting point of Ni. From this, it was found that the mixed powder prepared by using the WC powder having a low reactivity and a large amount of hard particles (having a Fss particle size of 2.0) had a relatively small sintered particle density.

The semi-molten particles in the HVOF flame at a high temperature (~2300 ° C) still undergo a reaction of forming a composition of (W,Cr) ₂ C, and thus are still related to the reactivity of the particles. Therefore, the mixed grinding porcelain powder has a smaller particle size and a higher coating deposition rate. The intermediate particle diameters of the mixed-grinded porcelain gold powders of No. 1, 2, and 3 prepared by WC powders having Fss particle diameters of 2.5 μm, 2.0 μm, and 1.5 μm were 7.2 μm, 6.7 μm, and 5.5 μm, respectively. The stacking rates of the layers were 38.1%, 40.2% and 40.2%, respectively. The mixed-grinding porcelain powder of No. 2 has a lower primary particle reactivity in the granulated powder, resulting in a lower sintered density, and the average particle size of the granulated and sintered particles is relatively large, being 34.9 μm. Therefore, the semi-melting reaction of the coating formed by the mixed-grinding porcelain powder of No. 2 after spraying is not as good as the porcelain gold powder of No. 1, but the granulated powder (corresponding to the secondary particles) has a small particle density of 3.39 g. /cm ³ , so the corresponding particle strength is small, and the deposition efficiency of the coating is high under the absence of splashing during the spray coating process. However, the porosity of the coating formed by the raw material of No. 2 is relatively large, 1.05%, higher than 1%; and the hardness (Hv0.3) is low, 952, less than 1000.

Please refer to Table 1 again. The porcelain powders of No. 4, 1, 5 and 6 use WC powder with Fss particle size of 2.5 μm, and Cr ₃ C ₂ powder and Ni powder with stirring grinding time of 30 minutes and 1 hour respectively. 73 wt% WC-20 wt% Cr ₃ C ₂ -7 wt% Ni porcelain gold powder formulated at 3 hours and 6 hours. The intermediate particle diameters of the porcelain gold powders Nos. 4, 1, 5 and 6 were 8.4 μm, 7.2 μm, 5.8 μm and 3.7 μm, respectively; the bulk densities of the granulated and sintered powders were 3.54 g/cm ³ and 3.61 g/cm, respectively. ³ , 3.78g/cm ³ and 3.76g/cm ³ , roughly increasing phenomenon; the average particle diameter of the granulated and sintered powders are 27.2μm, 29.9μm, 35.4μm and 34.4μm, respectively; the flow rates are respectively 1.78g/sec, 1.92g/sec, 2.38g/sec and 2.17g/sec, also showed an increasing phenomenon; and the deposition rate of the coating was 37.3%, 38.1%, 41.2% and 45.6%, respectively. Increase the phenomenon.

Since the bulk density of the granulated and sintered powder is larger, the stronger the particle strength, the less likely it is to cause splashing, which theoretically may lower the coating deposition rate. However, the bulk density of less than 3.8 g/cm ^{3 can} still reach a coating accumulation ratio of 40% or more, as long as the intermediate particle diameter of the mixed abrasive powder is less than 5.5 μm. Similarly, the larger particle size of the granulated and sintered powder does not cause a decrease in the coating deposition rate, which also highlights the importance of small particle size and high activity of the mixed grinding. Further, as can be seen from Table 1, the effect of the weight ratio of the portion having a particle diameter of less than 38 μm in the granulated and sintered powder on the coating deposition rate is not regular.

The porcelain gold powder of No. 7 was prepared by grinding the Cr ₃ C ₂ powder to have an intermediate particle diameter of 2.9 μm, and then grinding the Cr ₃ C ₂ powder and the WC powder having a Fss particle diameter of 1.5 μm and the middle. Ni powder having a particle diameter of 12.4 μm was mixed and ground for 1 hour. The obtained mixed abrasive had an intermediate particle diameter of 4.5 μm. Sintering was carried out at a lower temperature, and the bulk density of the obtained granulated and sintered powder was 3.54 g/cm ³ , and the deposition efficiency of the sprayed coating was 43.6%. Compared with the powder of No. 3, it can be shown that the smaller the intermediate particle size of the mixed abrasive powder, the smaller the bulk density. Moreover, in the molten state in which no splash is generated, the smaller the bulk density, the larger the coating stacking efficiency, and the greater the hardness of the coating.

Nos. 8, 9 and 10 are granulated and sintered powders obtained after increasing the sintering temperature. The porcelain gold powder of No. 8 was granulated by mixing and mixing the WC powder having a Fss particle size of 2.5 μm, the Cr ₃ C ₂ powder having an intermediate particle diameter of 3.8 μm, and the Ni powder having an intermediate powder of 12.4 μm for 3 hours. Further, sintering was carried out at a temperature of 1,350 ° C to 1,400 ° C to obtain a granulated and sintered powder having a density of 3.99 g/cm ³ . The other powder size characteristics of No. 8 porcelain gold powder are similar to those of No. 5, and the fluidity is worse than that of No. 5 porcelain gold powder, but the coating deposition efficiency is low only 35.9%, which is far less than the 41.2 powder of No. 5 powder. %. The porcelain gold powders Nos. 9 and 10 were also prepared from WC powder having a Fss particle size of 2.5 μm, and the mixed abrasive powder had an intermediate particle diameter of 7.2 μm as the number 1 porcelain gold powder. The granulated powders Nos. 9 and 10 were sintered at a relatively high temperature of 1350 ° C to 1400 ° C, and the bulk density of the obtained granulated and sintered powder was increased to 3.86 g/cm ³ and 3.91 g/cm ^{3 , respectively} . No. 1 and the cermet powder of a bulk density of 3.61g / cm ³ as compared to the coating deposition efficiency is gradually decreased down to 38.1% and the 33.1%.

The relationship between the intermediate particle diameter of the mixed abrasive powder of the porcelain powders numbered 1, 5, 8, 9, and 10 and the bulk density of the granulated and sintered powder and the deposition efficiency of the coating were compared. If the bulk density of the granulated and sintered powder is too high, and it is 3.75 g/cm ³ or more, the intermediate particle diameter of the mixed abrasive powder needs to be less than 5.5 μm to obtain a coating deposition efficiency of more than 40%.

It is apparent from the above embodiments that one of the advantages of the present invention is that the method of the present invention can improve carbides by controlling the particle size of the raw material, the particle size of the agitated mixture, and/or the bulk density of the granulated powder after sintering. The deposition rate of the spray coating of porcelain gold powder. Therefore, the amount of porcelain gold powder required for each roller of the high-speed oxygen flame spray coating can be greatly reduced, thereby reducing the production cost of the roller.

While the present invention has been described above by way of example, it is not intended to be construed as a limitation of the scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

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Claims (8)

A method for producing a carbide porcelain gold powder, comprising: providing a raw material comprising: a plurality of tungsten carbide powders having a content of 73% by weight; a plurality of chromium carbide powders having a content of 20% by weight; and a plurality of 7% by weight a nickel powder; a mixed grinding treatment of the raw material to obtain a mixed abrasive, wherein the mixed abrasive has an intermediate particle diameter of less than or equal to 6.7 μm; and the granulation treatment is performed on the mixed abrasive Obtaining a plurality of carbide particles; and subjecting the carbide particles to a sintering treatment to obtain a plurality of carbide porcelain gold powders. The method for producing a carbide porcelain gold powder according to claim 1, wherein the particle size of the snow particles of each of the tungsten carbide powders is from 1.5 μm to 2.5 μm. The method for producing a carbide china gold powder according to claim 1, wherein the carbide powders have an average particle diameter of from 15 μm to 45 μm. The method for producing a carbide porcelain gold powder according to claim 1, wherein the mixed abrasive has an intermediate particle diameter of less than or equal to 5.5 μm. The method for producing a carbide porcelain gold powder according to claim 4, wherein the carbide gold powder has a bulk density of less than or equal to 3.81 g/cm ³ . The method for producing a carbide-based porcelain gold powder according to claim 1, wherein the particle size of the snow-containing particles of each of the tungsten carbide powders is 1.5 μm, and the intermediate particle diameter of the tungsten carbide powders is less than or equal to 3.5 μm; The intermediate particle diameter of the chromium carbide powder is 3.8 μm; the intermediate particle diameter of the nickel powder is 12.4 μm; the intermediate particle diameter of the mixed abrasive is less than or equal to 5.5 μm; and the bulk density of the carbide gold powder Less than or equal to 3.80 g/cm ³ . The method for producing a carbide porcelain gold powder according to claim 1, wherein the particle size of the snow particles of each of the tungsten carbide powders is from 2.0 μm to 2.5 μm, and the intermediate particles of the tungsten carbide powders are less than or equal to 5.4. Mm; the intermediate particle diameter of the chromium carbide powder is 3.8 μm; the intermediate particle diameter of the nickel powder is 12.4 μm; the intermediate particle diameter of the mixed abrasive is less than or equal to 5.5 μm; and the carbide gold powder The bulk density is less than or equal to 3.75 g/cm ³ . The method for producing a carbide porcelain gold powder according to claim 1, wherein the temperature of the sintering treatment is 1200 ° C to 1400 ° C.