Post-treatment process for tough and wear-resistant thermal spraying metal ceramic coating

Abstract

The invention discloses a post-treatment process for a tough wear-resistant thermal spraying metal ceramic coating, and relates to the field of material processing, the thermal spraying metal ceramic coating is subjected to annealing treatment, and decomposition, oxidation and decarburization of a WC hard phase in the heat treatment process are inhibited by setting a vacuum environment, a heating temperature, a heating speed, a heat preservation temperature, heat preservation time and a cooling speed; the thermal spraying metal ceramic coating is obtained by spraying powder composed of WC, Cr3C2, Co or CoNi through hypersonic flame spraying. Crystallization of an amorphous binding phase structure is achieved, a carbide hard phase is separated out from elements dissolved in a binding phase in a solid mode, and dual strengthening of combination of a matrix phase and a phase interface is obtained due to element diffusion of the phase interface. The post-heat treatment process for the metal ceramic coating disclosed by the invention is simple to operate and high in implementation feasibility, and provides reference for preparation of matrix phase and phase interface double-strengthened tough metal ceramic.

Description

Technical Field

[0001] This invention relates to the field of materials processing, and specifically to a post-treatment process for a strong, wear-resistant thermal spray metal-ceramic coating. Background Technology

[0002] Wear accounts for approximately 60-80% of all scrapped parts due to surface failure. High-hardness and toughness wear-resistant coatings can improve the surface strength of parts and enhance their wear resistance, which is one of the main ways to extend the life of parts.

[0003] Metal-ceramics, composed of a metal or alloy as the binder phase and a ceramic particle as the hard phase, are among the most widely used integral wear-resistant materials and surface coatings for parts. The metal or alloy binder phase provides the strength and toughness of the cermet, while the hard ceramic particles provide its high hardness, forming a structure that resists wear. Cermetics are widely used in metal cutting, rock drilling, rock quarrying, stone cutting, metal forming dies, and wear-resistant parts, becoming an important material in the field of wear-resistant engineering.

[0004] As tool materials develop towards higher precision, higher efficiency, higher reliability, and specialization, cermet materials are required to possess not only high hardness but also high toughness to meet the wear resistance requirements under complex working conditions. However, cermets are inherently brittle materials, and there is a mutually restrictive relationship between hardness, strength, toughness, and wear resistance: high hardness tends to result in lower toughness, and vice versa. The development direction of cermets is to achieve a coordinated improvement in hardness, strength, toughness, and wear resistance. Besides the wear conditions (load, abrasive characteristics), the wear resistance of cermet materials is related to the hardness, grain size, and distribution of the hard phase. Under different loads and abrasive conditions, the wear resistance of cermet materials is related to the carbide particle size; different particle sizes of hard phases have different effects on improving the wear resistance of coatings. Multi-scale hard phase and well-crystallized binder phase have high wear resistance due to the synergistic effect of hardness and toughness. However, in spray coatings, the hard phase dissolves in the binder phase, and the amorphization and formation of multi-component hard and brittle phases of the binder phase during rapid cooling reduce the toughness of the binder phase and the strengthening effect of the hard phase, thus reducing the wear resistance of the cermet material.

[0005] Therefore, how to design the post-heat treatment process of thermal spray metal ceramic coating based on the evolution characteristics of the binder phase, and solve the problem of "the formation of non-equilibrium binder phase structure due to the dissolution of hard phase and rapid cooling during the coating deposition process, and the realization of the dispersion precipitation of nano hard phase, crystallization of binder phase structure and strengthening of phase interface bonding in post-heat treatment of coating", is the key problem that needs to be solved in the development of tough and wear-resistant metal ceramic coating. Summary of the Invention

[0006] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a post-treatment process for a strong, wear-resistant thermal spray metal-ceramic coating.

[0007] The technical solution of the present invention is as follows:

[0008] A post-treatment process for a tough and wear-resistant thermal spray metal-ceramic coating involves annealing the thermal spray metal-ceramic coating and suppressing the decomposition, oxidation and decarburization of the WC hard phase during the heat treatment process by setting the vacuum environment, heating temperature and heating rate, holding temperature, holding time and cooling rate.

[0009] The thermally sprayed metal-ceramic coating is obtained by spraying powder composed of WC, Cr3C2, Co, or CoNi with a supersonic flame.

[0010] Preferably, the vacuum environment for the annealing process is -0.1 MPa.

[0011] Preferably, in the annealing process, the heating rate during the heating stage is set according to the following temperature ranges: 2℃ / min for 0-200℃, 1.5℃ / min for 200-300℃, 1.0℃ / min for 300-400℃, 1.0℃ / min for 400-500℃, 0.5℃ / min for 500-600℃, 0.5℃ / min for 600-700℃, 0.5℃ / min for 700-800℃, and 0.5℃ / min for 800-900℃.

[0012] Preferably, in the annealing process, the holding temperature and time during the heating stage are as follows: 5 min at 200℃, 10 min at 300℃, 15 min at 400℃, 20 min at 500℃, 20 min at 600℃, 25 min at 700℃, 30 min at 800℃, and 120 min at 900℃.

[0013] Preferably, in the annealing process, the cooling rate during the cooling stage is set according to the following temperature ranges: 0.5℃ / min for 900-800℃, 0.5℃ / min for 800-700℃, 0.5℃ / min for 700-600℃, 0.5℃ / min for 600-500℃, 1℃ / min for 500-400℃, 1.5℃ / min for 400-300℃, and 2℃ / min for 300-200℃.

[0014] Preferably, the holding temperature and time of the cooling stage are: 30 min at 800℃, 20 min at 700℃, 15 min at 600℃, 15 min at 500℃, 10 min at 400℃, 10 min at 300℃, and 5 min at 200℃.

[0015] The beneficial effects of this invention are:

[0016] This invention provides a post-treatment process for a strong, tough, and wear-resistant thermal spray metal-ceramic coating that achieves dual reinforcement based on the matrix phase and phase interface. By annealing the thermal spray metal-ceramic coating, and by designing a reasonable vacuum environment, heating temperature and rate, holding temperature, holding time, and cooling rate, the decomposition, oxidation, and decarburization of the WC hard phase during the heat treatment process are suppressed. This achieves the crystallization of the amorphous binder phase, the precipitation of carbides from elements dissolved in the binder phase, and the dual reinforcement of the matrix phase and phase interface due to element diffusion.

[0017] The heat treatment process following the coating of the metal-ceramic disclosed in this invention is simple to operate and highly feasible to implement, providing a reference for the preparation of strong and tough metal-ceramics with dual reinforcement of the matrix phase and the phase interface. Attached Figure Description

[0018] Figure 1 These are the cross-sectional microstructures of the coating before and after heat treatment; where a: low magnification of the sprayed state; b: high magnification of the sprayed state; c: low magnification of the heat-treated state; d: high magnification of the heat-treated state;

[0019] Figure 2 It refers to the coating phase structure before and after heat treatment; where 3: sprayed state; 3-1: heat treatment 1. Detailed Implementation

[0020] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0021] Example 1

[0022] According to the present invention, a post-treatment process for a strong, tough, and wear-resistant thermal spray metal-ceramic coating based on dual reinforcement of the matrix phase and phase interface is used to post-treat a 74.8WC-13.2Cr3C2-12Co metal-ceramic coating sprayed by supersonic flame. The thermal spraying process parameters are as follows: oxygen pressure 0.6MPa, flow rate 530splm; fuel gas (C3H8) pressure 0.45MPa, flow rate 45splm; powder delivery gas (N2) pressure 0.55MPa, flow rate 46splm; spraying distance 180mm; powder delivery rate 110g / min; spray gun moving speed 450mm / s; spray gun step distance 4mm / step.

[0023] Post-processing includes the following steps:

[0024] S1. Construct a post-processing vacuum environment. Load the sprayed 74.8WC-13.2Cr3C2-12Co coating into a sealable quartz tube. Use a vacuum pump to reduce the pressure inside the tube to -0.1MPa, and seal the interface with a flame-melted end cap.

[0025] S2. Setting Heating Temperature and Rate: A stepped heating and heat preservation system is adopted. The heating rates for different temperature ranges are: 0-200℃: 2.5℃ / min; 200-300℃: 2℃ / min; 300-400℃: 1.0℃ / min; 400-500℃: 1.0℃ / min; 500-600℃: 0.5℃ / min; 600-700℃: 0.5℃ / min; 700-800℃: 0.5℃ / min; 800-900℃: 0.5℃ / min.

[0026] S3. Set the holding temperature and holding time for the heating stage: 200℃ for 5 minutes; 300℃ for 10 minutes, 400℃ for 10 minutes, 500℃ for 15 minutes, 600℃ for 20 minutes, 700℃ for 20 minutes, 800℃ for 30 minutes, and 900℃ for 120 minutes.

[0027] S4. Set the cooling rate: 0.5℃ / min for 900-800℃, 0.5℃ / min for 800-700℃, 0.5℃ / min for 700-600℃, 0.5℃ / min for 600-500℃, 1℃ / min for 500-400℃, 1.5℃ / min for 400-300℃, and 2℃ / min for 300-200℃.

[0028] Step 5: Set the holding temperature and time for the cooling stage: 30 min for 800℃, 30 min for 700℃, 20 min for 600℃, 20 min for 500℃, 10 min for 400℃, 10 min for 300℃, and 5 min for 200℃.

[0029] Performance tests were conducted on Example 1, and the results are as follows:

[0030] Figure 1 This is the microstructure of the coating before and after treatment in Example 1. Figure 1 Images a and b show the cross-sectional microstructure of the 74.8WC-13.2Cr3C2-12Co cermet coating applied by supersonic flame spraying. Figure 1 Images c and d show the cross-sectional microstructure of the 74.8WC-13.2Cr3C2-12Co cermet coating after heat treatment. It can be seen that the interface between the hard phase (white area) and the binder phase (light gray area) in the coating is improved after heat treatment, changing from the original smooth interface... Figure 1 (b) evolved into a sawtooth interface. Figure 1(d) and hard phase precipitation appeared in the matrix phase (white fine particles appeared on the gray matrix, and gray fine particles appeared on the white or light gray matrix).

[0031] Figure 2 The XRD diffraction patterns of the coatings before and after post-treatment in Example 1 are shown; it can be seen that the XRD curves of the sprayed coating ( Figure 2 Some bumps are observed on the XRD pattern of the coating in the 2θ38-45° range (in the middle curve 3). The XRD pattern of the coating after heat treatment (…) Figure 2 The absence of amorphous bulges in the 2θ38-45° range on curve 3-1 indicates that the amorphous phase in the sprayed coating has essentially disappeared after heat treatment. Furthermore, the intensity of the WC characteristic peak in the coating has increased, while the peak width has decreased, indicating improved crystallinity of the phases in the coating. Weak Cr7C3 and Cr phases also appeared in the XRD pattern of the coating after heat treatment. 23 The C6 characteristic peak was retained, as were the characteristic peaks of Cr3C2, Cr2O3, and Cr2O5. However, the XRD pattern of the coating after heat treatment did not reveal the ternary hard and brittle phase (M). 12 The peaks of C and M6C indicate that heat treatment can improve the phase structure and morphology of the coating.

[0032] The test results of microhardness, fracture toughness, and wear rate before and after the coating post-treatment in Example 1 are shown. It was found that the microhardness, elastic modulus, fracture toughness, and wear rate of the post-heat-treated coating were 13.93±1.76 GPa, 220.48±49.11 GPa, and 6.95±2.01 MPa·m, respectively. 1 / 2 and 0.68±0.08×10 -2 mg / (Nm), compared to the microhardness, elastic modulus, fracture toughness and wear rate of the sprayed coating (11.83±1.43GPa, 181.47±28.81GPa, 3.17±1.32MPa·m), respectively. 1 / 2 and 1.38±0.32×10 -2After heat treatment, the microhardness and fracture toughness of the coating were significantly improved, the elastic modulus was increased, and the wear rate was significantly lower than that of the sprayed coating. To compare the performance with commercial powder-deposited coatings, coatings were deposited with commercial WC-12Co powder using the same thermal spraying process parameters (oxygen pressure 0.6MPa, flow rate 530splm; fuel gas (C3H8) pressure 0.45MPa, flow rate 45splm; powder delivery gas (N2) pressure 0.55MPa, flow rate 46splm; spraying distance 180mm; powder feed rate 110g / min; spray gun moving speed 450mm / s; spray gun step distance 4mm / step) and performance tests were conducted. The results indicate that the microhardness, elastic modulus, and fracture toughness of the heat-treated coating are significantly higher than those of the commercial WC-12Co powder-deposited coating (microhardness 11.05±25.75, elastic modulus 68.14±21.94 GPa, fracture toughness 1.64±0.2), while the wear rate is significantly lower than that of the sprayed coating and the commercial WC-12Co powder-deposited coating (3.99±0.23×10). -2 mg / (N·m)).

[0033] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. The above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various other corresponding changes and modifications based on the technical solutions and concepts described above, and all such changes and modifications should fall within the scope of protection of the claims of the present invention.

Claims

1. A post-treatment process for a tough and wear-resistant thermal spray metal-ceramic coating, characterized in that, Annealing of thermally sprayed metal-ceramic coatings is performed by setting the vacuum environment, heating temperature and heating rate, holding temperature, holding time, and cooling rate to suppress the decomposition, oxidation, and decarburization of the WC hard phase during the heat treatment process. The thermally sprayed metal-ceramic coating is obtained by spraying powder composed of WC, Cr3C2, Co, or CoNi with a supersonic flame.

2. The post-treatment process for a tough and wear-resistant thermal spray metal-ceramic coating according to claim 1, characterized in that, The vacuum environment for the annealing process is -0.1 MPa.

3. The post-treatment process for a tough and wear-resistant thermal spray metal-ceramic coating according to claim 1, characterized in that, In the annealing process, the heating rate during the heating stage is set according to the following temperature ranges: 2℃ / min for 0-200℃, 1.5℃ / min for 200-300℃, 1.0℃ / min for 300-400℃, 1.0℃ / min for 400-500℃, 0.5℃ / min for 500-600℃, 0.5℃ / min for 600-700℃, 0.5℃ / min for 700-800℃, and 0.5℃ / min for 800-900℃.

4. The post-treatment process for a tough and wear-resistant thermal spray metal-ceramic coating according to claim 1, characterized in that, In the annealing process, the holding temperature and time during the heating stage are as follows: 5 min at 200℃, 10 min at 300℃, 15 min at 400℃, 20 min at 500℃, 20 min at 600℃, 25 min at 700℃, 30 min at 800℃, and 120 min at 900℃.

5. The post-treatment process for a tough and wear-resistant thermal spray metal-ceramic coating according to claim 1, characterized in that, In the annealing process, the cooling rate during the cooling stage is set according to the following temperature ranges: 0.5℃ / min for 900-800℃, 0.5℃ / min for 800-700℃, 0.5℃ / min for 700-600℃, 0.5℃ / min for 600-500℃, 1℃ / min for 500-400℃, 1.5℃ / min for 400-300℃, and 2℃ / min for 300-200℃.

6. The post-treatment process for a tough and wear-resistant thermal spray metal-ceramic coating according to claim 1, characterized in that, The holding temperature and time for the cooling stage are as follows: 30 min at 800℃, 20 min at 700℃, 15 min at 600℃, 15 min at 500℃, 10 min at 400℃, 10 min at 300℃, and 5 min at 200℃.

Images