A method for characterizing and analyzing the particle spreading behavior of a HVOF with an inclination angle

Abstract

The present application relates to the technical field of surface engineering, in particular to a method for characterizing and analyzing the particle spreading behavior of HVOF with an inclination angle, comprising: establishing a numerical calculation model of HVOF spray gun, a numerical calculation model of a single spraying particle, and a numerical calculation model of a substrate with different angles / curvatures; making a spraying particle receiving substrate and a spraying particle sieve plate with the same angle aperture, which are made of the same material; collecting a single spraying particle under the current spraying angle; obtaining the spreading form of a single spraying particle under actual HVOF process test; judging whether the numerical simulation result is accurate; and verifying the microstructure characteristics and performance. On the one hand, the present application realizes the characterization of the spreading form of a single particle at different HVOF spraying angles through numerical simulation and test, and on the other hand, the present application establishes the mapping relationship among the spraying process, the particle spreading form and the coating quality at different angles by combining numerical simulation with test verification.

Description

Technical Field

[0001] This invention relates to the field of surface engineering technology, specifically to a method for characterizing and analyzing the spreading behavior of HVOF particles with tilt angle. Background Technology

[0002] High-velocity oxygen fuel (HVOF) spraying, as a process for surface modification and strengthening of parts, is widely used to improve surface properties, dimensional repair, and preventative maintenance of parts due to its advantages such as high coating density, wear resistance, low heat-affected zone, strong bonding strength, and environmental friendliness. Traditional HVOF processes assume that the optimal coating quality is achieved when the sprayed particle stream is at a 90° angle to the substrate. However, maintaining a fixed 90° angle is nearly impossible when spraying complex-shaped parts, necessitating the development of angled HVOF spraying processes. However, the heating, flight, impact, spreading, and cooling of HVOF particles is almost a transient process, making it difficult to characterize the spreading morphology of individual particles. Furthermore, the HVOF process involves numerous parameters such as oxygen-fuel ratio, nozzle velocity, and spraying distance; introducing the spraying angle parameter further complicates the optimization of angled HVOF processes.

[0003] Regarding the study of particle behavior during HVOF (High-Voltage-Flame) spraying, a search revealed patent CN202111141180.1, which discloses a numerical analysis method for the particle motion characteristics of nickel-based alloy powder during HVOF spraying. This method uses numerical simulation to explore the influence of flame flow on particle behavior during HVOF spraying. However, this method only provides process parameters such as oxygen-fuel ratio and particle flight velocity and melting characteristics through numerical simulation, without addressing the particle spreading behavior and its impact at different spraying angles. Furthermore, most published literature directly presents the coating performance obtained at a certain spraying angle or numerically simulates the particle spreading behavior at 90° spraying. No reports have been found on establishing a mapping relationship between spraying process, particle spreading morphology, and coating quality at different HVOF angles by characterizing particle spreading behavior at different angles. The spreading behavior of HVOF particles with tilt angles directly affects coating porosity, bonding strength and other indicators. Therefore, it is particularly important to propose a method for characterizing and analyzing the spreading behavior of HVOF particles with tilt angles and to establish the mapping relationship between spraying process, particle spreading morphology and coating quality at different angles. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for characterizing and analyzing the spread behavior of HVOF particles at different angles. By narrowing the process window through numerical simulation, a visual representation of the particle spread morphology at different angles is provided. The numerical simulation results are then verified through the collection and characterization of individual particles and the detection of coating performance during actual process implementation. This establishes a mapping relationship between the spraying process, particle spread morphology, and coating quality at different angles.

[0005] The technical problem to be solved by this invention is achieved by the following technical solution:

[0006] A method for characterizing and analyzing the spreading behavior of HVOF particles with tilt angles, comprising the following steps:

[0007] Step (1) Based on the actual part size characteristics, establish numerical calculation models for the HVOF spray gun, individual spray particles, and substrates with different angles / curvatures.

[0008] Step (II) According to the HVOF spraying process, set the combustion model in the spray gun model, set the boundary conditions in the spray gun model, set the fuel flow rate, combustion improver flow rate, spraying angle simulation process parameters, and set the physical property parameters of the sprayed powder particles and the substrate. Among them, the simulation process parameters of the spraying angle are 45°~90°.

[0009] Step (3) Inject the spray powder particles into the spray gun, simulate the temperature of the particles and the speed of the aircraft, and obtain the numerical simulation results of the particle spreading morphology under the current spraying angle.

[0010] Step (iv) Based on the actual part size characteristics, determine the spraying angle and the radius of curvature of the spraying substrate, and manufacture a spraying particle receiving substrate and a spraying particle sieve plate with the same material and the same angle of holes.

[0011] Step (5) Based on the parameters set in Step (2), conduct an actual HVOF process experiment, and use the sieve plate and receiving substrate in Step (4) to collect individual sprayed particles at the current spraying angle.

[0012] Step (6) Use SEM to characterize a single sprayed particle at the current spraying angle to obtain the spreading morphology of a single sprayed particle under the actual HVOF process test.

[0013] Step (VII) Compare the numerical simulation results of particle spreading morphology under the current spraying angle in Step (III) with the characteristics of single particle trailing length, width, and number of scattered particles in the spreading morphology of a single sprayed particle under the actual HVOF process test in Step (V). Determine whether the numerical simulation results in Step (III) are accurate. If accurate, proceed to Step (VIII). If inaccurate, optimize the numerical model and simulation conditions and parameter settings, and feed back to Step (I) and Step (II).

[0014] Step (8) Spray the workpiece according to the current HVOF process and spraying angle, and verify the microstructure characteristics and performance. Based on the characterization and verification test results, evaluate the influence of the spraying angle on the coating quality and determine whether the coating performance quality is qualified. If it is qualified, proceed to step (9). If it is not qualified, optimize the HVOF process with angle and feed back to step (5).

[0015] Step (9) Curing the angled HVOF process and improving the database.

[0016] Preferably, in step (i), full constraints are applied to the bottom surface of the numerical calculation model of the matrix with different angles / curvatures, and surface symmetry constraints are applied to the 1 / 4 symmetry plane between the particle and the matrix, while the other surfaces of the model are in a free state.

[0017] Preferably, the matrix temperature in the numerical calculation model of the matrix with different angles / curvatures is set to room temperature, the particle-matrix collision contact adopts the surface-to-surface contact algorithm, the impact elastic response adopts the linear elastic model, and it is assumed that the particle and the matrix will not separate once they come into contact.

[0018] Preferably, the boundary conditions in step (ii) include inlet boundary conditions, outlet boundary conditions, and wall boundary conditions.

[0019] Preferably, the inlet boundary condition is set to an inlet mass flow rate ratio of 1:3.

[0020] Preferably, the outlet boundary condition is set to the pressure outlet boundary.

[0021] Preferably, the wall boundary condition is set to a non-slip wall, and the wall temperature is set to a constant 500K.

[0022] Preferably, in step (ii), the simulated process flow rate parameter of the fuel is 0.01 to 0.02 kg / s and the simulated process flow rate parameter of the combustion improver is 0.03 to 0.06 kg / s.

[0023] Preferably, in step (ii), the powder feeding rate is 47-57 g / min and the spraying distance is 320-340 mm.

[0024] Preferably, in step (iv), the surface roughness of the receiving substrate is ≤Ra0.01μm, the thickness of the sieve plate is 2-5mm, the sieve hole diameter is 0.5-1mm, the sieve hole spacing is 10-15mm, and the opening angle of the sieve plate is parallel to the spraying angle.

[0025] The beneficial effects of this invention are:

[0026] This invention provides a method for characterizing and analyzing the spread behavior of HVOF particles at different angles. On the one hand, it characterizes the spread morphology of individual particles at different HVOF spraying angles through both numerical simulation and experimentation. On the other hand, by combining numerical simulation and experimental verification, it explores the influence of spraying angle on particle spread morphology in HVOF, further verifies the performance quality of HVOF coatings at different angles, and establishes the mapping relationship between spraying process, particle spread morphology, and coating quality at different angles. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0028] Figure 1 A schematic diagram of HVOF spraying with an angle and the collection of a single particle;

[0029] Figure 2 Flowchart for characterizing and analyzing the spreading behavior of HVOF particles with angles. Detailed Implementation

[0030] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] like Figure 1 and Figure 2 As shown, a method for characterizing and analyzing the spreading behavior of HVOF particles with tilt angles includes the following steps:

[0032] Step (1) Based on the actual part size characteristics, establish numerical calculation models for the HVOF spray gun, individual spray particles, and substrates with different angles / curvatures.

[0033] Specifically, the numerical calculation model of the HVOF spray gun includes the combustion chamber, lavel tube, parallel tube, and air, and the mesh of complex areas inside the spray gun and particle-matrix contact areas is refined.

[0034] The numerical calculation model of the matrix with different angles / curvatures is fully constrained on the bottom surface, and surface symmetry constraint is applied on the 1 / 4 symmetry plane between the particle and the matrix. The other surfaces of the model are free. The matrix temperature is set to room temperature. The particle-matrix collision contact adopts the surface-to-surface contact algorithm. The impact elastic response adopts the linear elastic model, and it is assumed that the particle and the matrix will not separate once they come into contact.

[0035] Step (II) According to the HVOF spraying process, set the combustion model in the spray gun model, set the boundary conditions in the spray gun model, set the fuel flow rate, combustion aid flow rate, and spraying angle to simulate process parameters, set the physical property parameters of the sprayed powder particles and the substrate, and adjust the speed at which the sprayed powder particles are injected into the spray gun to ensure that the powder particles are delivered to the center of the flame.

[0036] Specifically, the boundary conditions include inlet boundary conditions, outlet boundary conditions, and wall boundary conditions. The inlet boundary condition is set to an inlet mass flow rate ratio of 1:3, the outlet boundary condition is set to a pressure outlet boundary, the wall boundary condition is set to a non-slip wall, and the wall temperature is set to a constant 500K.

[0037] The actual parameters for the HVOF spraying process are: fuel flow rate of 6.3–6.7 GPH, oxygen flow rate of 1910–2010 SCFH, powder feeding rate of 47–57 g / min, spraying distance of 320–340 mm, and spraying angle of 45°–90°.

[0038] The combustion model uses kerosene as fuel and oxygen as the combustion accelerant. The simulated process parameters are set based on actual spraying parameters: the simulated process flow rate for kerosene is 0.01–0.02 kg / s, and the simulated process flow rate for oxygen is 0.03–0.06 kg / s. The particle injection angle is 45°.

[0039] Step (3) Inject the spray powder particles into the spray gun, simulate the particle temperature and aircraft speed, and obtain the numerical simulation results of the particle spreading morphology at the current 45°.

[0040] Step (iv) Based on the actual part size characteristics, determine the spraying angle and the radius of curvature of the spraying substrate, and manufacture a spraying particle receiving substrate and a spraying particle sieve plate with the same material and the same angle of holes.

[0041] Specifically, the surface roughness of the receiving substrate is ≤Ra0.01μm, the thickness of the sieve plate is 2~5mm, the sieve hole diameter is 0.5~1mm, the sieve hole spacing is 10~15mm, and the opening angle of the sieve plate is parallel to the spraying angle.

[0042] Step (5) Based on the parameters set in Step (2), conduct an actual HVOF process experiment, and use the sieve plate and receiving substrate in Step (4) to collect the single sprayed particles at the current 45°.

[0043] Step (VI) Use SEM to characterize a single sprayed particle at the current 45° to obtain the spreading morphology of a single sprayed particle under the actual HVOF process test.

[0044] Step (VII) Compare the numerical simulation results of particle spreading morphology at the current 45° in Step (III) with the characteristics of single particle trailing length, width, and number of scattered particles in the spreading morphology of a single sprayed particle under the actual HVOF process test in Step (V). Determine whether the numerical simulation results in Step (III) are accurate. If accurate, proceed to Step (VIII). If inaccurate, optimize the numerical model and simulation conditions and parameter settings, and feed back to Step (I) and Step (II).

[0045] Step (8) Spray the furnace-fed parts according to the current HVOF process and spraying angle, and verify the microstructure characteristics and performance. The verification requirements include: coating porosity ≤1%, oxidation rate ≤1%, and bonding strength ≥70Mpa.

[0046] Based on the characterization and verification test results, evaluate the impact of the spraying angle on the coating quality, and determine whether the coating performance quality is qualified. If it is qualified, proceed to step (nine); if it is not qualified, optimize the angled HVOF process and feed back to step (five).

[0047] Step (9) Curing the angled HVOF process and improving the database.

[0048] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely prisms of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for characterizing and analyzing the spreading behavior of HVOF particles with tilt angle, characterized in that: The steps include the following: Step (1) Based on the actual part size characteristics, establish numerical calculation models for the HVOF spray gun, individual spray particles, and substrates with different angles / curvatures. In step (1), full constraints are applied to the bottom surface of the numerical calculation model of the matrix with different angles / curvatures, and surface symmetry constraints are applied to the 1 / 4 symmetry plane between the particle and the matrix. The other surfaces of the model are free. In the numerical calculation models of substrates with different angles / curvatures, the substrate temperature is set to room temperature, the particle-substrate collision contact adopts the surface-to-surface contact algorithm, the impact elastic response adopts the linear elastic model, and it is assumed that the particle and the substrate will not separate once they come into contact. Step (II) According to the HVOF spraying process, set the combustion model in the spray gun model, set the boundary conditions in the spray gun model, set the fuel flow rate, combustion aid flow rate, spraying angle simulation process parameters, and set the physical property parameters of the sprayed powder particles and the substrate. Among them, the simulation process parameters of the spraying angle are 45°~90°. Step (3) Inject the spray powder particles into the spray gun, simulate the temperature and flight speed of the particles, and obtain the numerical simulation results of the particle spreading morphology under the current spraying angle. Step (iv) Based on the actual part size characteristics, determine the spraying angle and the radius of curvature of the spraying substrate, and manufacture a spraying particle receiving substrate and a spraying particle sieve plate with the same material and the same angle of aperture. Step (5) Based on the parameters set in Step (2), conduct an actual HVOF process experiment, and use the sieve plate and receiving substrate in Step (4) to collect individual sprayed particles at the current spraying angle. Step (six) Use SEM to characterize a single sprayed particle at the current spraying angle to obtain the spreading morphology of a single sprayed particle under the actual HVOF process test. Step (VII) Compare the numerical simulation results of particle spreading morphology under the current spraying angle in Step (III) with the characteristics of single particle trailing length, width, and number of scattered particles in the spreading morphology of a single sprayed particle under the actual HVOF process test in Step (V). Determine whether the numerical simulation results in Step (III) are accurate. If accurate, proceed to Step (VIII). If inaccurate, optimize the numerical model and simulation conditions and parameter settings, and feed back to Step (I) and Step (II). Step (8) Spray the workpiece according to the current HVOF process and spraying angle, and perform microstructure characteristics and performance verification. Based on the characterization and verification test results, evaluate the influence of the spraying angle on the coating quality and determine whether the coating performance quality is qualified. If qualified, proceed to step (9). If not qualified, optimize the angled HVOF process and feed back to step (5). Step (nine) Curing the HVOF process with an angle and improving the database.

2. The method for characterizing and analyzing the spreading behavior of HVOF particles with tilt angle according to claim 1, characterized in that: The boundary conditions in step (ii) include inlet boundary conditions, outlet boundary conditions, and wall boundary conditions.

3. The method for characterizing and analyzing the spreading behavior of HVOF particles with tilt angle according to claim 2, characterized in that: The inlet boundary condition is set to an inlet mass flow rate ratio of 1:

3.

4. The method for characterizing and analyzing the spreading behavior of HVOF particles with tilt angle according to claim 2, characterized in that: The export boundary condition is set to pressure export boundary.

5. The method for characterizing and analyzing the spreading behavior of HVOF particles with tilt angle according to claim 2, characterized in that: The wall boundary conditions are set to non-slip wall, and the wall temperature is set to a constant 500K.

6. The method for characterizing and analyzing the spreading behavior of HVOF particles with tilt angle according to claim 1, characterized in that: In step (ii), the simulated process flow rate parameters for fuel are 0.01–0.02 kg / s and for combustion improver are 0.03–0.06 kg / s.

7. The method for characterizing and analyzing the spreading behavior of HVOF particles with tilt angle according to claim 1, characterized in that: In step (ii), the powder feeding rate is 47-57 g / min and the spraying distance is 320-340 mm.

8. The method for characterizing and analyzing the spreading behavior of HVOF particles with tilt angle according to claim 1, characterized in that: In step (iv), the surface roughness of the receiving substrate is ≤ Ra 0.01μm, the thickness of the sieve plate is 2-5mm, the sieve hole diameter is 0.5-1mm, the sieve hole spacing is 10-15mm, and the opening angle of the sieve plate is parallel to the spraying angle.

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