Method for preparing TiCN / Ni60 composite coating based on electromagnetic-assisted laser cladding technology

Abstract

The invention relates to the technical field of laser cladding composite coating preparation, in particular to a method for preparing a TiCN / Ni60 composite coating based on an electromagnetic-assisted laser cladding technology, and aims to solve the problems of large residual stress, uneven hard phase distribution, low production efficiency and the like in the traditional technology. The method comprises the following steps: firstly, premixing Ni60-based alloy powder, Ti powder and graphite powder, and carrying out ball milling to synthesize a TiCN phase; single-time cladding is adopted, and an electromagnetic composite field composed of a steady-state magnetic field, an alternating electric field and a high-frequency pulse magnetic field is applied to a molten pool area; and then pulse laser shock, low-temperature tempering and the like are carried out. The performance of the coating is optimized through composite field coupling, the technological process is simplified, the hardness of the coating is greatly improved, the abrasion rate is reduced, the porosity and residual stress are remarkably reduced, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser cladding composite coating preparation, and particularly relates to a method for preparing TiCN / Ni60 composite coating based on electromagnetic-assisted laser cladding technology. Background Art

[0002] The information disclosed in the background art of the present invention is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an indication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] In modern industry, the demand for high-performance coatings such as wear resistance and corrosion resistance is increasing day by day, especially in the fields of aerospace, automotive manufacturing, and heavy machinery. Laser cladding, as an advanced surface modification technology, has received extensive attention because it can provide high hardness, good wear resistance, and excellent bonding strength. However, when traditional laser cladding technology is used to prepare composite coatings reinforced with hard phases (such as TiCN), firstly, the large temperature gradient during the rapid heating and cooling process leads to the formation of residual stress, which is likely to cause crack and porosity problems, affecting the overall quality and service life of the coating. In addition, although the single use of electromagnetic field assistance can refine grains to a certain extent, its ability to regulate the molten pool flow is limited, resulting in hard phase segregation and further exacerbating the stress concentration phenomenon.

[0004] Secondly, the problem of uneven distribution of hard phases is also relatively prominent. In composite coatings such as TiCN / Ni60, the dispersion of TiCN particles directly affects the wear resistance of the coating. In traditional processes, due to the influence of molten pool convection, hard phases such as TiCN may be locally enriched or depleted, reducing the comprehensive performance of the coating.

[0005] Furthermore, the existing methods for preparing gradient coatings usually require multiple claddings, etching, and impact treatments, which not only increase the production cost but also significantly reduce the working efficiency. At the same time, although the application of the synchronous powder feeding method improves the production efficiency, its extremely high requirements for the accuracy of the powder feeding equipment, and problems such as uneven powder utilization rate may lead to coating thickness fluctuations or composition deviations.

[0006] Therefore, there is an urgent need to study a method for preparing TiCN / Ni60 composite coating by composite field-assisted laser cladding technology with stronger ability to regulate molten pool flow, more uniform distribution of hard phases, and higher production efficiency. Summary of the Invention

[0007] The purpose of the present invention is to make up for the deficiencies of the existing technology, and provides a method for preparing TiCN / Ni60 composite coating based on electromagnetic-assisted laser cladding technology. It aims to solve the limitations of single-field assistance, simplify the process flow, and improve the production efficiency and coating performance.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for preparing a TiCN / Ni60 composite coating based on electromagnetic-assisted laser cladding technology, comprising the following steps:

[0010] S1, Material pretreatment and composite powder preparation: Mix 75-85wt% of Ni60-based alloy powder, 5-15wt% of Ti powder, and 5-8wt% of graphite powder, and homogenize by ball milling after premixing; Synthesize the TiCN phase by reaction;

[0011] S2, Adopt electromagnetic composite field-assisted laser cladding: Adopt single-pass cladding, and apply an electromagnetic composite field in the molten pool area during laser cladding. The electromagnetic composite field includes a steady magnetic field, an alternating electric field, and a high-frequency pulsed magnetic field that act synergistically;

[0012] Among them, the steady magnetic field is used to suppress the turbulence of the molten pool and reduce spatter; the alternating electric field is used to drive the Lorentz force to stir the molten pool and promote the diffusion of Ti, C, and N; the high-frequency pulsed magnetic field is used to periodically interrupt dendrite growth and refine the grains to the sub-micron level;

[0013] S3, Use the electromagnetic composite field to regulate the distribution of the TiCN phase, form a TiCN content gradient from the surface to the inside, and use it to reduce the interface stress;

[0014] S4, Post-treatment process: Use pulsed laser to impact the surface of the coating to close micro-cracks and improve the density.

[0015] Preferably, the steady magnetic field is 0.8-1.2T, a permanent magnet array is used, and the direction is perpendicular to the cladding path to suppress the turbulence of the molten pool;

[0016] The alternating electric field is 50-100Hz, the current is 10-20A, and a periodic Lorentz force is generated through an electromagnetic coil to drive the convection of the molten pool;

[0017] The high-frequency pulsed magnetic field is 1-5kHz, the pulse width is 50-100μs, and it is superimposed on the steady magnetic field.

[0018] Preferably, during laser cladding, the surface power of the laser needs to be controlled at 1600-1800W to promote the synthesis of TiCN through high temperature, and the bottom layer power is 1100-1200W to inhibit excessive reaction.

[0019] Preferably, in step S4, the post-treatment process further includes a low-temperature tempering process, the temperature is set at 300-400°C and held for 2h to eliminate residual stress.

[0020] Preferably, during the low-temperature tempering process, an auxiliary tempering magnetic field is applied to promote dislocation recombination.

[0021] The present invention has at least the following beneficial effects:

[0022] Reducing cracks and pores: The electromagnetic field suppresses the turbulence of the molten pool and reduces the temperature gradient.

[0023] Homogenizing the distribution of hard phases: The combined action of the composite field controls the size of TiCN particles within 1 - 3 μm, improves the distribution uniformity, and enhances the wear resistance.

[0024] Improving process efficiency: A gradient structure is achieved in a single cladding, reducing the steps of traditional multi-layer cladding and greatly shortening the working hours.

[0025] Optimizing the bonding strength: Electromagnetic stirring enhances the metallurgical bonding between the molten pool and the substrate, improving the interfacial shear strength. Description of the Drawings

[0026] Figure 1 It is a schematic diagram of the overall process of the present invention. Detailed Embodiments

[0027] The present invention will be further described below in conjunction with specific embodiments and the drawings.

[0028] Embodiment 1

[0029] Step S1: Material pretreatment and composite powder preparation: Prepare raw materials with a composition ratio of 80 wt% Ni60-based alloy powder, 10 wt% Ti powder, and 6 wt% graphite powder. After premixing the above raw materials, put them into a ball mill for homogenization treatment. The ball milling time is 8 hours, and the ball-to-material ratio is 10:1. Subsequently, place the premixed powder in a reaction vessel and synthesize the TiCN phase through reaction under a high-temperature environment.

[0030] In step S1, for material pretreatment and composite powder preparation, a planetary ball mill with the model QM-3SP2 is selected. The rotation speed is set at 300 r / min. The material of the ball mill tank is stainless steel, lined with polyurethane to reduce the mixing of impurities during the ball milling process. The nitrogen flow rate is controlled at 5 L / min by a mass flow meter. The reaction temperature is set at 1000 °C, and the holding time is 2 hours to ensure the full synthesis of the TiCN phase.

[0031] Step S2: Using an electromagnetic composite field to assist laser cladding: Adopt a single cladding method. During the laser cladding process, apply an electromagnetic composite field to the molten pool area. This electromagnetic composite field is composed of a steady magnetic field, an alternating electric field, and a high-frequency pulsed magnetic field that act synergistically.

[0032] Steady magnetic field: With an intensity of 1 T, a permanent magnet array is used, and its direction is perpendicular to the cladding path, used to suppress the turbulence of the molten pool and reduce the splashing phenomenon.

[0033] Alternating electric field: The frequency is set to 80 Hz, the current is 15 A, and a periodic Lorentz force is generated through an electromagnetic coil to drive the convection of the molten pool and promote the diffusion of Ti, C, and N elements.

[0034] High-frequency pulsed magnetic field: The frequency is 3 kHz, the pulse width is 80 μs, and it is superimposed on the steady magnetic field to periodically interrupt dendrite growth and refine the grains to the sub-micron level.

[0035] During the laser cladding process, the surface power of the laser is controlled to be 1700 W to promote the synthesis of TiCN at high temperature; the bottom layer power is 1150 W to inhibit excessive reactions.

[0036] In step S2, an IPG-YLS-4000 fiber laser is used for the laser cladding equipment, and the spot diameter is 3 mm.

[0037] Step S3: Regulate the distribution of TiCN phase: Use an electromagnetic composite field to regulate the distribution of TiCN phase to form a TiCN content gradient from the surface to the inside, thereby reducing the interface stress.

[0038] Step S4: Post-treatment process: Pulse laser is used to impact the surface of the coating. The energy density of the pulse laser is 5 J / cm 2 , the frequency is 10 Hz, and the action time is 5 minutes to close microcracks and improve the density.

[0039] After testing, the average hardness of the prepared TiCN / Ni60 composite coating reaches HV1200, and the hardness is increased by about 30% compared with the traditional laser cladding coating. In the dry friction and wear experiment, the wear rate is 0.002 mg / (N·m), which is reduced by 40% compared with the traditional process. The TiCN particles inside the coating are evenly distributed, the average particle size is about 0.5 μm, the porosity is lower than 1%, and the residual stress is reduced to 150 MPa, significantly improving the comprehensive performance and service life of the coating.

[0040] Example 2

[0041] Step S1: Material pretreatment and composite powder preparation: Select raw materials with a composition ratio of 75 wt% Ni60-based alloy powder, 15 wt% Ti powder, and 5 wt% graphite powder. After premixing the raw materials, ball milling is carried out for homogenization. The ball milling time is 10 hours, and the ball-to-powder ratio is 12:1. Then nitrogen is introduced to synthesize the TiCN phase.

[0042] During the ball milling process in step S1, anhydrous ethanol is added to the ball milling tank as a process control agent, and the addition amount is 5% of the total powder mass to improve the fluidity and uniformity of the powder. When synthesizing the TiCN phase, the reaction pressure is maintained at 0.1 MPa, and the reaction temperature is monitored in real time through a thermocouple to ensure that the temperature fluctuation range is within ±10 °C.

[0043] Step S2: Assist laser cladding with an electromagnetic composite field: Also use single-pass cladding and apply an electromagnetic composite field.

[0044] Steady magnetic field: With an intensity of 1.2 T, the permanent magnet array is perpendicular to the cladding path to suppress the turbulence of the molten pool.

[0045] Alternating electric field: With a frequency of 100 Hz and a current of 20 A, a Lorentz force is generated through the electromagnetic coil to drive the convection of the molten pool.

[0046] High-frequency pulsed magnetic field: With a frequency of 5 kHz and a pulse width of 100 μs, it is superimposed on the steady magnetic field to refine the grains.

[0047] During laser cladding, the surface layer power is controlled at 1800 W, and the bottom layer power is 1200 W. Specifically, the scanning speed of laser cladding is set at 8 mm / s, and the overlapping rate is 40%. In the electromagnetic composite field equipment, the steady magnetic field is generated by a permanent magnet system of model HGMS-1.2T, the alternating electric field is generated by an electromagnetic generator of model ACF-100, and the high-frequency pulsed magnetic field is provided by a pulsed magnetic field generating device of model HPMS-5K.

[0048] Step S3: Regulate the distribution of TiCN phase: Use the electromagnetic composite field to form a TiCN content gradient and reduce the interface stress.

[0049] Step S4: Post-treatment process: First, use pulsed laser to impact the surface of the coating, with an energy density of 6 J / cm 2 , a frequency of 12 Hz, and an action time of 6 minutes. Then, perform a low-temperature tempering process, with the temperature set at 300 °C, holding for 2 h, and at the same time applying an auxiliary tempering magnetic field with a magnetic field intensity of 0.3 T to promote dislocation recombination and eliminate residual stress.

[0050] The hardness of the composite coating prepared in this example reaches HV1300, and the wear rate is further reduced to 0.0015 mg / (N·m). Through electron microscope observation, the TiCN grains are refined to 0.3 μm and are distributed in a gradient in the coating, with the TiCN content in the surface layer being 35% and in the bottom layer being 15%, effectively reducing the interface stress. The density of the coating reaches 99.5%, and the fatigue life is increased by 50% compared with the traditional process, showing excellent performance in practical applications.

[0051] Example 3

[0052] Step S1: Material pretreatment and composite powder preparation: The raw material composition ratio is 85 wt% Ni60-based alloy powder, 5 wt% Ti powder, and 8 wt% graphite powder. After premixing, ball milling is carried out for 6 hours with a ball-to-material ratio of 8:1 to synthesize the TiCN phase.

[0053] When premixing the powder in step S1, use a three-dimensional mixer for mixing. The mixing time is 2 hours to ensure uniform mixing of the powder. During the synthesis of the TiCN phase, the nitrogen concentration in the reaction vessel is monitored in real time, and the nitrogen supplement amount is adjusted to maintain the concentration above 95%.

[0054] Step S2: Electromagnetic composite field-assisted laser cladding: Single-pass cladding with the application of an electromagnetic composite field.

[0055] Steady magnetic field: The intensity is 0.8 T, which inhibits the turbulence of the molten pool.

[0056] Alternating electric field: The frequency is 50 Hz and the current is 10 A, which drives the convection of the molten pool.

[0057] High-frequency pulsed magnetic field: The frequency is 1 kHz and the pulse width is 50 μs, which refines the grains.

[0058] During laser cladding, the surface layer power is 1600 W and the bottom layer power is 1100 W. Specifically, the defocus amount of laser cladding is set to +2 mm to optimize the shape and size of the molten pool.

[0059] Step S3: Regulate the distribution of the TiCN phase: Form a TiCN content gradient through the regulation of the electromagnetic composite field.

[0060] Step S4: Post-treatment process

[0061] Pulse laser impacts the surface of the coating with an energy density of 4 J / cm 2 , a frequency of 8 Hz, and an action time of 4 minutes. The low-temperature tempering temperature is 400 °C, the holding time is 2 h, and the auxiliary tempering magnetic field intensity is 0.2 T to eliminate residual stress.

[0062] To more intuitively demonstrate the advantages of the preparation method of the present invention, the performance data of the above three examples are compared with those of the traditional laser cladding technology, as shown in the following table:

[0063]

[0064] It can be clearly seen from the data comparison and the bar chart that the TiCN / Ni60 composite coating prepared by the electromagnetic-assisted laser cladding technology of the present invention is significantly superior to the traditional laser cladding process in terms of hardness, wear resistance, porosity, and residual stress, fully demonstrating the remarkable advantages of the method of the present invention.

[0065] In summary, the present invention addresses the problems existing in the traditional technology, such as large residual stress, uneven distribution of hard phases, and low production efficiency. The method first premixes and ball-mills Ni60-based alloy powder, Ti powder, and graphite powder to synthesize TiCN phase; single-pass cladding is adopted, and an electromagnetic composite field composed of a steady magnetic field, an alternating electric field, and a high-frequency pulsed magnetic field is applied in the molten pool area to form an interface stress with a decreasing TiCN content gradient; then, treatments such as pulsed laser shock and low-temperature tempering are carried out. Dual-channel powder feeding avoids powder oxidation loss. The present invention optimizes the coating performance through the coupling of the composite field, simplifies the process flow, increases the coating hardness by 30%-40%, reduces the wear rate, significantly reduces the porosity and residual stress, and improves the production efficiency.

[0066] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference may be made to each other.

[0067] The terms "upper", "lower", "outer side", "inner side", etc. in the specification and claims of the present invention, if any, are used to distinguish the relative relationships in position and do not need to be qualitatively defined. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion.

[0068] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a TiCN / Ni60 composite coating based on electromagnetic-assisted laser cladding technology, characterized in that, It includes the following steps: S1, Material pretreatment and composite powder preparation: Mix powders with a composition ratio of 75 - 85 wt% of Ni60-based alloy powder, 5 - 15 wt% of Ti powder, and 5 - 8 wt% of graphite powder. After premixing, homogenize them by ball milling; synthesize TiCN phase; S2, Electromagnetic composite field-assisted laser cladding: Adopt single-pass cladding, and apply an electromagnetic composite field to the molten pool area during laser cladding. The electromagnetic composite field includes a steady magnetic field, an alternating electric field, and a high-frequency pulsed magnetic field that act synergistically; Among them, the steady magnetic field is used to suppress the turbulence of the molten pool and reduce spatter; the alternating electric field is used to drive the Lorentz force to stir the molten pool and promote the diffusion of Ti, C, and N; the high-frequency pulsed magnetic field is used to periodically interrupt dendrite growth and refine the grains to the submicron level; S3, Use the electromagnetic composite field to regulate the distribution of the TiCN phase, form a TiCN content gradient from the surface to the interior, and use it to reduce the interfacial stress; S4, Post-treatment process: Use pulsed laser to impact the surface of the coating to close microcracks and improve the density.

2. The method for preparing a TiCN / Ni60 composite coating based on electromagnetic-assisted laser cladding technology according to claim 1, characterized in that: The steady magnetic field is 0.8 - 1.2 T, and a permanent magnet array is used, with the direction perpendicular to the cladding path to suppress the turbulence of the molten pool; The alternating electric field is 50 - 100 Hz, and the current is 10 - 20 A. Periodic Lorentz force is generated through an electromagnetic coil to drive the convection of the molten pool; The high-frequency pulsed magnetic field is 1 - 5 kHz, and the pulse width is 50 - 100 μs, which is superimposed on the steady magnetic field.

3. The method for preparing a TiCN / Ni60 composite coating based on electromagnetic-assisted laser cladding technology according to claim 1, characterized in that: During laser cladding, the power of the laser needs to be controlled such that the surface layer power is 1600 - 1800 W to promote the synthesis of TiCN through high temperature, and the bottom layer power is 1100 - 1200 W to inhibit excessive reaction.

4. The method for preparing a TiCN / Ni60 composite coating based on electromagnetic-assisted laser cladding technology according to any one of claims 1 to 3, characterized in that: In step S4, the post-treatment process further includes a low-temperature tempering process, with the temperature set at 300 - 400 °C and held for 2 h to eliminate residual stress.

5. The method for preparing a TiCN / Ni60 composite coating based on electromagnetic-assisted laser cladding technology according to claim 4, characterized in that: During the low-temperature tempering process, an auxiliary tempering magnetic field is applied to promote dislocation recombination.

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