Plasma coaxial rear tungsten carbide particle wear-resistant coating surfacing welding gun and method thereof

Abstract

The plasma coaxial rear tungsten carbide particle wear-resistant coating surfacing welding gun comprises a welding gun body, a nozzle and a tungsten electrode shrunk inwards in the middle of the interior of the nozzle, a protective cover is arranged on the periphery of the nozzle, a protective gas channel is formed between the nozzle and the protective cover, and a base powder channel and a particle channel are arranged between the nozzle and the tungsten electrode. The base powder channel and the particle channel are arranged on the inner side of the shielding gas channel in an embedded mode, the outlet end of the base powder channel and the outlet end of the particle channel are located below the nozzle, and the distance between the particle channel and a nozzle center hole of the nozzle is about 3-8 mm. Precision coaxial coupling of the particle flow, the electric arc and the molten pool is achieved, the particles are heated more evenly, kinetic energy transmission is more sufficient, the fusion rate and distribution uniformity of the particles in the molten pool are improved, splashing is reduced, the fusion effect and distribution uniformity of the tungsten carbide particles in the molten pool are remarkably improved, and the service life of the tungsten carbide particles is prolonged. And finally, the tungsten carbide reinforced wear-resistant coating with high hardness, low porosity and strong bonding degree is obtained.

Description

Technical Field

[0001] This invention relates to the field of material surface engineering technology, specifically to a plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch and method. Background Technology

[0002] Tungsten carbide (WC) possesses extremely high hardness (above HV2400) and wear resistance, making it widely used for surface strengthening and repair of easily worn parts in mining machinery, oil drilling, and agricultural machinery. Introducing tungsten carbide particles into a metal matrix through welding to form a composite coating is an effective method for improving workpiece life.

[0003] Currently, when using arc welding (such as MIG, MAG, TIG) to deposit tungsten carbide particles, non-coaxial (external) particle feeding methods or fine powder of 100-400 mesh are commonly used. The main problems are as follows:

[0004] (1) Uneven particle distribution: Particles are fed from the outside of the welding torch and are easily affected by arc blow and airflow disturbance. They are difficult to accurately enter the center of the arc and the optimal area of ​​the molten pool, resulting in uneven particle distribution in the coating, with local enrichment or depletion.

[0005] (2) Poor fusion: The particles entering from the outside are not heated evenly. Some particles may only be swept by the edge of the electric arc and fall into the molten pool or splash out without being fully heated, resulting in poor fusion, weak interface bonding, easy detachment, and high porosity.

[0006] (3) Particle burn-off and splashing: Particles are exposed to the high-temperature arc zone for a relatively long time, which increases the risk of oxidation burn-off; at the same time, lateral impact on the molten pool can easily cause molten pool disturbance and particle splashing, resulting in low material utilization.

[0007] (4) The particles have low kinetic energy. Because the particles are fed from the outside, the angle of the particle channel is large, which will reduce the kinetic energy of the particles. The impact on the molten pool is small, and the depth of entry into the molten pool is shallow.

[0008] (5) Coating performance fluctuation: The above factors lead to unstable key properties of the coating such as hardness, wear resistance, and density, making it difficult to meet the requirements of high-end applications. Summary of the Invention

[0009] The purpose of this invention is to provide a plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch and method for overlaying a tungsten carbide particle-reinforced wear-resistant composite coating on the surface of a metal substrate, so as to solve the problems existing in the prior art.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A plasma coaxial tungsten carbide particle wear-resistant coating welding torch includes a torch body, a nozzle, and a tungsten electrode recessed in the middle of the nozzle. A protective cover is provided around the nozzle, and a protective gas channel is provided between the nozzle and the protective cover. A base powder channel and a particle channel are respectively provided between the nozzle and the tungsten electrode. The base powder channel and the particle channel are nested inside the protective gas channel, and the outlet ends of the base powder channel and the particle channel are located below the nozzle. The particle channel is about 3-8 mm away from the nozzle center hole of the nozzle.

[0012] Furthermore, the main channel portions of the base powder channel and the particle channel are both coaxial with the axis of the tungsten electrode.

[0013] Furthermore, the base powder channel adopts a design with two or three powder outlet holes.

[0014] Furthermore, the particle channel inside the nozzle 6 is an inverted cone shape, smaller at the top and larger at the bottom, with a circular arc elliptical opening at the lower end.

[0015] Furthermore, the end of the particle channel forms an angle of 15-22 degrees with the axis of the welding torch.

[0016] Furthermore, the particle channel is located on the rear side of the welding torch travel direction.

[0017] Furthermore, the gas transported through the protective gas channel is an inert gas or a mixture of inert gases.

[0018] Furthermore, the welding torch body is provided with cooling water channels for cooling the tungsten electrode and nozzle.

[0019] Furthermore, both the base powder channel and the particle channel are connected upstream of a powder feeder with adjustable powder feeding speed and flow rate.

[0020] The welding method for plasma coaxial post-positioned tungsten carbide particle wear-resistant coating overlay welding torch includes the following steps:

[0021] 1) An electric arc is ignited on the surface of the substrate to form a molten pool;

[0022] 2) Protective gas flows out from the protective gas channel, forming a protective gas shield;

[0023] 3) Base powder with a particle size range of 100-270 mesh is supplied by a powder feeder and transported to the molten pool through the base powder channel along the central axis of the welding torch;

[0024] 4) Tungsten carbide particles are fed into the liquid molten pool formed in the high-temperature zone of the arc center through the particle channel 3-8 mm behind the center arc in the direction of the welding torch travel, and are fully protected by inert gas.

[0025] 5) Tungsten carbide particles that are heated evenly and have high kinetic energy impact the molten pool at an angle of 15-22 degrees and quickly penetrate into the molten metal;

[0026] 6) The welding torch moves along the set trajectory, and after the molten pool solidifies, a wear-resistant composite coating of uniformly dispersed tungsten carbide particles is formed.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] (1) The present invention can significantly improve the coating quality: the tungsten carbide particles have a high fusion rate (>95%), uniform distribution, good interfacial metallurgical bonding, low porosity (<2%), and the coating hardness (HV can reach 1800-2200) and wear resistance are greatly improved.

[0029] (2) The present invention can reduce splashing and oxidation: the coaxial rear design greatly reduces particle splashing loss (material utilization rate is increased by 15-30%) and exposure time in the high temperature zone, effectively suppressing the oxidation and burning loss of WC particles;

[0030] (3) The process of this invention is stable and efficient: the inherent advantages of the coaxial rear structure ensure the stability of the process, good consistency of coating quality, and high production efficiency.

[0031] (4) This invention has wide applicability: it is particularly suitable for surface strengthening and repair of various steel substrates that require high wear resistance. Attached Figure Description

[0032] Figure 1 This is the front view of the present invention;

[0033] Figure 2 This is a bottom view of the present invention;

[0034] Figure 3 and Figure 4 The images show the surface formation effect when welding with the existing technology and the welding gun of the present invention, respectively (it can be seen that the surface particles of the present invention are better coated, the weld bead is cleaner, and there is no welding slag on the side).

[0035] Figure 5 and Figure 6 These are schematic diagrams showing the spatter situation during welding with the existing technology and the welding gun of the present invention (the present invention has no spatter under the protection of coaxial inert gas);

[0036] Figure 7 and Figure 8 The diagrams show the minimum thickness of the weld overlay when using the welding guns of the prior art and the present invention, respectively (the weld overlay thickness of the present invention is more controllable);

[0037] Figure 9 and Figure 10The images are metallographic diagrams of welding torches used in the prior art and the present invention, respectively (the particles welded by the present invention are more uniform and have a higher density).

[0038] In the diagram: 1-Shielding gas channel; 2-Base powder channel; 3-Nozzle center hole; 4-Particle channel; 5-Tungsten electrode; 6-Nozzle; 7-Protective cover; 8-Welding torch body. Detailed Implementation

[0039] The technical solution of this patent will be further described in detail below with reference to specific embodiments.

[0040] Please see Figure 1-2 The plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch includes a torch body 8, a nozzle 6, and a tungsten electrode 5 recessed in the middle of the nozzle 6. A protective cover 7 is provided around the nozzle 6, and a protective gas channel 1 is formed between the nozzle 6 and the protective cover 7. The protective gas channel 1 surrounds the protective cover 7 around the nozzle 6, and the molten pool solidifies under the full protection of the inert gas. A base powder channel 2 and a particle channel 4 are respectively provided between the nozzle 6 and the tungsten electrode 5. The base powder channel 2 and the particle channel 4 are nested inside the protective gas channel 1, and the outlet ends of the base powder channel 2 and the particle channel 4 are located below the nozzle 6. The particle channel 4 is about 3-8 mm away from the nozzle center hole 3 of the nozzle 6, forming a "post-positioned coaxial" structure.

[0041] The main channels of the base powder channel 2 and the particle channel 4 are coaxial with the axis of the tungsten electrode 5. The particle channel 4 inside the nozzle 6 is an inverted cone shape, wider at the bottom than the top, with a circular elliptical opening at the lower end. The end of the particle channel 4 forms an angle of 15-22 degrees with the welding torch axis, and the particle channel 4 is positioned behind the direction of the welding torch travel to ensure that the arc forms a molten pool first, and then the carbide particles enter the molten pool at a certain angle, which is beneficial for the dispersion of particles when entering the molten pool. Four-way gas supply and three-way powder supply or two-way powder supply and one-way particle supply are used to ensure that the state of the arc is minimally affected. Coaxial powder and particle supply reduces disturbance to the arc, reduces interference to the molten pool, and reduces spatter. The gas transported by the shielding gas channel 1 is an inert gas or a mixture of inert gases. The welding torch body 8 is equipped with a cooling water channel for cooling the tungsten electrode 5 and the nozzle 6. The upstream of both the base powder channel 2 and the particle channel 4 are connected to powder feeders with adjustable powder feeding speed and flow rate.

[0042] The welding method using the aforementioned plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch includes the following steps:

[0043] 13) An electric arc is ignited on the surface of the substrate to form a molten pool;

[0044] 14) Protective gas (such as Ar, Ar+H2) flows out from protective gas channel 1 to form a protective gas shield;

[0045] 15) The base powder (iron-based and nickel-based powders with a particle size range of 100-270 mesh are used as base powders for bonding) is supplied by the powder feeder and conveyed to the molten pool through the base powder channel 2 along the central axis of the welding torch;

[0046] 16) Tungsten carbide particles are fed into the liquid molten pool formed in the high-temperature zone of the arc center, 3-8 mm behind the center arc, in the direction of the welding torch travel, and are fully protected by inert gas.

[0047] 17) Tungsten carbide particles that are heated evenly and have high kinetic energy impact the molten pool at an angle of 15-22 degrees and quickly penetrate into the molten metal;

[0048] 18) The welding torch moves along the set trajectory, and after the molten pool solidifies, a wear-resistant composite coating of uniformly dispersed tungsten carbide particles is formed.

[0049] See Figure 3-10 Compared with the existing non-coaxial (lateral) particle feeding technology, the coaxial rear-feeding particle feeding of this invention shows that the particle coating on the surface of the invention is better, the weld bead is cleaner, there is no weld slag, there is no spatter under the protection of coaxial inert gas, the weld thickness is more controllable, and the welded particles are more uniform and denser. The differences in characteristics between the two and the advantages of this invention are shown in Table 1 below:

[0050] Table 1

[0051]

[0052] This invention solves the problems of uneven particle distribution, low fusion rate, excessive spatter, and high risk of oxidation and burn-off in existing non-coaxial (lateral) powder feeding technologies, as well as the potential for premature heating of particles or impact on weld beads caused by pre-coaxial powder feeding. It achieves precise coaxial coupling between the particle flow, the electric arc, and the molten pool, resulting in more uniform particle heating and more complete kinetic energy transfer. This significantly improves the fusion rate and distribution uniformity of particles in the molten pool, optimizes the residence time and quantity of particles in the high-temperature zone, reduces spatter, and significantly enhances the fusion effect and distribution uniformity of tungsten carbide particles in the molten pool. Ultimately, it yields a tungsten carbide-reinforced wear-resistant coating with high hardness, low porosity, and strong adhesion.

[0053] The embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch, characterized in that, The welding torch includes a welding torch body (8), a nozzle (6), and a tungsten electrode (5) recessed in the middle of the nozzle (6). A protective cover (7) is provided around the nozzle (6). A protective gas channel (1) is formed between the nozzle (6) and the protective cover (7). A base powder channel (2) and a particle channel (4) are respectively provided between the nozzle (6) and the tungsten electrode (5). The base powder channel (2) and the particle channel (4) are nested inside the protective gas channel (1). The outlet ends of the base powder channel (2) and the particle channel (4) are located below the nozzle (6). The particle channel (4) is about 3-8 mm away from the nozzle center hole (3) of the nozzle (6).

2. The plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch according to claim 1, characterized in that, The main channel portions of the base powder channel (2) and particle channel (4) are coaxial with the axis of the tungsten electrode (5).

3. The plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch according to claim 1, characterized in that, The base powder channel (2) adopts a design with two or three powder outlet holes.

4. The plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch according to claim 1, characterized in that, The particle channel (4) inside the nozzle (6) is an inverted cone shape with a smaller upper part and a larger lower part, and the lower end outlet is an arc-shaped elliptical opening.

5. The plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch according to claim 1, characterized in that, The end of the particle channel (4) forms an angle of 15-22 degrees with the axis of the welding torch.

6. The plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch according to claim 1, characterized in that, The particle channel (4) is located on the rear side of the welding torch travel direction.

7. The plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch according to claim 1, characterized in that, The protective gas channel (1) delivers an inert gas or a mixture of inert gases.

8. The plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch according to claim 1, characterized in that, The welding torch body (8) is provided with cooling water channels for cooling the tungsten electrode (5) and the nozzle (6).

9. The plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch according to claim 1, characterized in that, Both the base powder channel (2) and the particle channel (4) are connected upstream of a powder feeder with adjustable powder feeding speed and flow rate.

10. A method for surfacing using a plasma coaxial post-positioned tungsten carbide particle wear-resistant coating welding torch as described in any one of claims 1-9, characterized in that, Includes the following steps: 1) An electric arc is ignited on the surface of the substrate to form a molten pool; 2) The protective gas flows out from the protective gas channel (1) to form a protective gas shield; 3) Base powder with a particle size range of 100-270 mesh is supplied by a powder feeder and transported to the molten pool through the base powder channel (2) along the central axis of the welding torch; 4) Tungsten carbide particles are fed into the liquid molten pool formed in the high-temperature zone of the arc center at a distance of 3-8 mm behind the center arc by the particle channel (4) in the direction of the welding torch travel, and are fully protected by inert gas. 5) Tungsten carbide particles that are heated evenly and have high kinetic energy impact the molten pool at an angle of 15-22 degrees and quickly penetrate into the molten metal; 6) The welding torch moves along the set trajectory, and after the molten pool solidifies, a wear-resistant composite coating of uniformly dispersed tungsten carbide particles is formed.

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