CN110760845A - Anti-oxidation high-hardness wear-resistant coating on titanium alloy surface and preparation method thereof - Google Patents

Abstract

The invention belongs to the field of titanium alloy surface engineering, in particular to an anti-oxidation, high-hardness and wear-resistant coating on the surface of titanium alloy and a preparation method. The coating is prepared by coaxial powder feeding laser cladding technology; the cladding powder is recorded in mass percentage, including 75wt% TC4 and 25wt% NiCr-Cr ₃ C ₂ powder. The coaxial powder feeding laser cladding technology can precisely control the forming quality, reduce the finishing workload in the coating application process, and improve the efficiency. Cr ₃ C ₂ powder has a low melting point, and there will be no unmelted particles during processing. At the same time, Cr ₃ C ₂ powder has good hardness at room temperature and high temperature. The composite powder NiCr-Cr ₃ C ₂ can be formed during laser cladding. The elements required for the strengthening phase can also provide Ni and Cr elements for solid solution strengthening of the matrix. Ti6Al4V powder alleviates the excessive thermal property difference between the reinforcing phase and the substrate, and can play a certain role in buffering deformation.

Description

A kind of titanium alloy surface anti-oxidation high-hardness wear-resistant coating and preparation method

technical field

The invention belongs to the field of titanium alloy surface engineering, in particular to an anti-oxidation, high-hardness and wear-resistant coating on the surface of titanium alloy and a preparation method.

Background technique

Titanium alloy has the characteristics of low density, high specific strength and strong corrosion resistance. It is widely used in the fields of aviation, aerospace, shipbuilding, and marine engineering equipment, and plays an irreplaceable role in the advancement and lightweight of equipment. Taking aviation aircraft as an example, the aircraft fuselage material is gradually transitioning from traditional aluminum alloy materials to carbon fiber reinforced materials (CFRP), and some high-strength steel components such as frames and joints are also replaced by titanium alloys to reduce weight. This is because titanium alloys have the characteristics of light weight and high strength, and at the same time, they have similar physical properties to carbon fiber reinforced materials, and can avoid potential corrosion when used as joint materials. In addition, titanium alloys can also be used as engine materials, mainly used as fan and compressor blades and other components that serve at lower temperatures (<600/℃). Ti-6Al-4V (TC4) is the most widely used titanium alloy with excellent specific strength, excellent corrosion resistance and fracture toughness, as well as good weldability and ability to withstand extreme temperatures, and can be processed by heat treatment strengthen. The poor friction and wear performance of titanium alloy surfaces has always been a bottleneck restricting its development. In order to improve the friction and wear properties of titanium alloy surfaces, there are currently some related patents for preparing wear-resistant coatings on titanium alloy surfaces, as shown in Table 1.

Table 1 Related patents of wear-resistant coating on titanium alloy surface

The No. 1 and No. 2 patents in the above table both use chemical plating to prepare the wear-resistant coating, which is not only complicated in the method and steps, but also uses more acidic and alkaline reagents in the preparation process, which is highly toxic to the environment and human body; No. 3 The patent is that H13 powder needs to be cold sprayed in the laser cladding process, the powder needs to be prepared by special treatment, and the spraying steps are complicated; The deformation coordination ability between the various phases is poor, and defects such as cracks are prone to occur, so rare earth elements are required to improve the coating quality; Patent No. 5 prepares the laser wear-resistant coating by the pre-powder method, and the pre-powder preparation process will also contact Acidic, alkaline and toxic reagents have great potential safety hazards, and the prefabricated powder method is difficult to control. The volatilization of the binder during processing will cause coating defects, and the prefabricated coating is easy to fall off.

SUMMARY OF THE INVENTION

Aiming at the problems existing in the prior art, the purpose of the present invention is to provide an anti-oxidation, high-hardness and wear-resistant coating on the surface of a titanium alloy which can improve the friction and wear properties of the surface of the titanium alloy and a preparation method thereof.

In order to achieve the above object, the concrete technical scheme adopted in the present invention is:

An anti-oxidation, high-hardness, wear-resistant coating on the surface of a titanium alloy, the coating is prepared by coaxial powder feeding laser cladding technology; the cladding powder is recorded by mass percentage, including 75wt% TC4 and 25wt% NiCr _- Cr3 C ₂ powder.

Further, the measured chemical composition of the TC4 powder is recorded by mass percentage, including 89.27wt% Ti, 6.22wt% Al, 4.32wt% V, and the rest are Fe, C, H, O, N.

Further, the measured chemical composition of the NiCr-Cr ₃ C ₂ powder is recorded by mass percentage, including 19.59wt% Ni, 10.28wt% C, and the rest is Cr.

Further, the particle size distribution of the TC4 powder is 53-150 μm.

Further, the particle size distribution of the NiCr-Cr ₃ C ₂ mixed powder is 100-150 μm.

Further, the preparation method of the above-mentioned titanium alloy surface anti-oxidation high-hard wear-resistant coating comprises the following steps:

S1. Test the purchased Ti6Al4V substrate and cladding powder to ensure the quality of cladding;

S2. Sandblast the substrate to be clad, the surface roughness _Ra of the test block after sandblasting is about 1.98-2.07 μm; put the sandblasted test block in alcohol, carry out ultrasonic cleaning for 2-5 minutes, and then blow dry Put into a 99.9% pure argon protective box;

S3. Put the cladding powder into the ball mill according to the proportion for ball milling and powder mixing. The mixing time is more than 12 hours. Put the mixed powder into a vacuum drying box, and dry it at a constant temperature of 80 °C for more than 10 hours until before the cladding process. Then take it out from the constant temperature drying box and put it into the powder feeder;

S4. Use a coaxial powder feeding laser to clad the cladding powder on the test block to be clad.

Further, the cladding parameters of S4 are as follows: the multi-pass lap rate is 50%, the laser focal length is 16mm, the laser power is 700-1100W, the scanning speed is 0.4m/min, the powder feeding rate is 1.4r/min, and the spot diameter is It is 3.0mm, the powder feeding gas is helium, the gas flow rate is 7.0L/min, the whole process of cladding is protected by argon gas, and the gas flow rate is 8-15L/min.

The advantages and positive effects of the present invention are:

The invention provides an oxidation-resistant, high-hardness and wear-resistant coating on the surface of a titanium alloy and a preparation method. By adjusting the process, the wear-resistant coating without air and hole cracks can be prepared on the surface of the titanium alloy. The coaxial powder feeding laser cladding technology can precisely control the forming quality, reduce the finishing workload in the coating application process, and improve the efficiency. Cr ₃ C ₂ powder has a low melting point, and there will be no unmelted particles during processing. At the same time, Cr ₃ C ₂ powder has good hardness at room temperature and high temperature. The composite powder NiCr-Cr ₃ C ₂ can provide the formation of laser cladding process. The elements required for the strengthening phase can also provide Ni and Cr elements for solid solution strengthening of the matrix. Ti6Al4V powder alleviates the excessive thermal property difference between the reinforcing phase and the substrate, and can play a certain role in buffering deformation.

In addition, compared with the preparation of wear-resistant coating on the surface of titanium alloy by chemical plating, the dosage of strong oxidizing, strong corrosive and toxic chemical reagents in the present invention is less, which reduces the toxicity to the human body and the environment during the operation; the process of the present invention is less. , The operation is simple and easy to implement, which can improve the wear resistance of the titanium alloy surface and prolong the service period of the titanium alloy components; the phase in the present invention is simple, and the reinforcing phase TiC _x improves the surface hardness of the titanium alloy and realizes wear resistance at the same time. and anti-oxidation function; defects such as cracks and pores in the present invention change significantly with the increase of laser power, which is helpful for scientific researchers to study the influence of power on the macroscopic quality of laser cladding.

Description of drawings

Fig. 1 is the morphology of mixed powder in embodiment 1-3 of the present invention;

Fig. 2 is a graph showing the results of color penetrant inspection on the surface of cladding samples in Examples 1-3 of the present invention; a, Example 1; b, Example 2; c, Example 3;

Fig. 3 is the X-ray diffraction detection result diagram of utilizing D8 ADVANCE type X-ray diffractometer to carry out the present invention to the cladding sample in 3;

Fig. 4 is the result graph of using OLYMPUS metallographic microscope to count the enhancement phase of the sample of Example 1-3;

Figure 5 is a graph of the results of statistics on the porosity of the samples of Examples 1-3 using OLYMPUS metallographic microscope;

Fig. 6 is the result diagram of macroscopic morphology of the cladding samples in Examples 1-3 using HITACHI S-3000 scanning electron microscope; a, Example 1; b, Example 2; c, Example 3;

Figure 7 shows the results of the microstructure and morphology of the cladding samples in Examples 1-3 using a HITACHI S-3000 scanning electron microscope; a, Example 1; b, Example 2; c, Example 3;

Figure 8 is the analysis results of Ni and Cr elements of the coating in Example 3 by using JXA-8530F Plus field emission electron probe spectrometer; a, Ni elements; b, Cr elements;

FIG. 9 shows the microhardness test results of the coating in Example 3 using a KB30SR-FA digital Vickers hardness tester.

Detailed ways

In order to further understand the content, features and effects of the present invention, the following embodiments are given as examples, and are described in detail as follows in conjunction with the accompanying drawings:

The invention discloses an anti-oxidation, high-hardness and wear-resistant coating on the surface of titanium alloy, which is prepared by coaxial powder feeding laser cladding technology; NiCr-Cr ₃ C ₂ powder.

The coaxial powder feeding laser cladding technology can precisely control the forming quality, reduce the finishing workload in the coating application process, and improve the efficiency.

The composition of TC4 material is Ti-6Al-4V, which belongs to (α+β) type titanium alloy and has good comprehensive mechanical and mechanical properties; TC4 powder can increase the compatibility of cladding powder and titanium-based materials, and avoid the linear expansion coefficient The difference in physical and chemical properties such as thermal conductivity and thermal conductivity is too large to cause cracks; Ti6Al4V powder alleviates the excessive thermal physical property difference between the reinforcing phase and the substrate, and can play a certain role in buffering deformation.

NiCr-Cr ₃ C ₂ is a ceramic hybrid material with low melting point and density, no unmelted particles will exist during processing, and Cr ₃ C ₂ powder has good normal temperature and high temperature hardness, composite powder NiCr-Cr ₃ C ₂ can provide the elements required for the formation of the reinforcing phase during the laser cladding process, and can also provide Ni and Cr elements for the solid solution strengthening of the matrix. It is an anti-friction and wear material with excellent comprehensive properties;

Preferably, the measured chemical composition of the Ti6Al4V powder is recorded by mass percentage, including 89.27wt% Ti, 6.22wt% Al, 4.32wt% V and the rest are Fe, C, H, O, N; the powder particle size distribution is 53-150μm.

Preferably, the measured chemical composition of the NiCr-Cr ₃ C ₂ powder is recorded by mass percentage, including 19.59wt% Ni, 10.28wt% C, the rest is Cr, and the powder particle size distribution is 100-150 μm.

The invention also discloses a preparation method of the anti-oxidation, high-hardness and wear-resistant coating on the surface of the titanium alloy, comprising the following steps:

S1. Test the purchased Ti6Al4V substrate and cladding powder to ensure the quality of cladding;

S2. Pre-treatment of the substrate to be clad;

S3. Pretreatment of the cladding powder;

S4. Use a coaxial powder feeding laser to clad the cladding powder on the test block to be clad.

In S1, the stains on the surface of the titanium alloy sheet to be processed are first cleaned with anhydrous ethanol, and the substrate to be clad is cut into 100×100×10mm cladding test blocks with an EDM cutting machine;

In S2, the cladding test block is pre-treated, specifically: sandblasting the cladding test block to remove the surface oxide layer and dirt, and at the same time, it can also improve the roughness of the cladding test block and improve the laser energy. The absorption rate of the test block after sandblasting is about 1.98~ _2.07μm ; the test block after sandblasting is put into alcohol, ultrasonically cleaned for 2~5min, dried and put in 99.9% pure argon in the gas protective box.

In S3, the cladding powder is pretreated, specifically: put the cladding powder into a ball mill for ball milling and powder mixing according to the proportion, and the mixing time is more than 12 hours. Dry at a constant temperature for more than 10 hours, and then take it out of the constant temperature drying box and put it into the powder feeder until the cladding process to ensure the fluidity of the powder.

S4 uses a coaxial powder feeding laser to clad the cladding powder on the test block to be clad. The cladding parameters are as follows: the multi-pass lap rate is 50%, the laser focal length is 16mm, and the laser power is 700/900/1100W. The scanning speed is 0.4m/min, the powder feeding rate is 1.4r/min, the spot diameter is 3.0mm, the powder feeding gas is helium, and the gas flow rate is 7.0L/min. The whole cladding process is protected by argon gas, and the gas flow rate It is 8～15L/min.

Example 1

The specific scheme of this case is 75wt% TC4+25wt% NiCr-Cr ₃ C ₂ , the laser power is 700W, and the laser cladding coating is prepared according to the above steps.

Embodiment 2

The specific scheme of this case is 75wt% TC4+25wt% NiCr-Cr ₃ C ₂ , the laser power is 900W, and the laser cladding coating is prepared according to the above steps.

Embodiment 3

The specific scheme of this case is 75wt% TC4+25wt% NiCr-Cr ₃ C ₂ , the laser power is 1100W, and the laser cladding coating is prepared according to the above steps.

Test Example

The morphology of the above mixed powder is shown in Figure 1; it can be seen that the TC4 powder is spherical powder and the NiCr-Cr3C2 powder is quasi-spherical. The powders with these two morphologies ensure good fluidity during cladding processing. It can be seen that the two powders are evenly mixed, which can ensure the quality of cladding.

The cladding samples of Examples 1-3 were subjected to surface color penetration testing, and the results were shown in Figure 2; it can be seen that the surface cracks of the cladding samples gradually decreased with the increase of power, and a very high power was obtained when the power was 1100W (Example 3). Good suppression, the best implementation effect.

The X-ray diffraction test results of the above cladding samples are shown in Figure 3; it can be seen that the phase in the cladding layer is the ceramic reinforcing phase TiCx, and the base phase is α-Ti.

The reinforcement phase of the above samples was counted by metallographic microscope, and the results are shown in Figure 4; the porosity was counted, and the results were shown in Figure 5: the number of reinforcement phases determines the oxidation resistance and wear resistance of the coating. In general, the higher the number of reinforcing phases, the better the performance of the laser cladding layer. It goes without saying that the more pores, the worse the macroscopic quality of the coating and the worse the performance of the coating. When the power is 1100W (Example 3), the number of reinforcing phases in the cladding layer is the largest, the porosity is the lowest, and the implementation effect is the best.

The macro-morphological results of the above cladding samples are shown in Figure 6; it can be seen that with the increase of laser power, the cracks and pores in the cross-section of the cladding layer are effectively suppressed, and the effect is the best at 1100W (Example 3). it is good.

The microstructure and morphology are shown in Figure 7: it can be seen that with the increase of power, the morphology of the enhanced phase TiCx of the coating transitions from granular to dendritic, but there are still cracks at lower power, so comprehensive consideration , the optimal power is 1100 (Example 3).

As shown in Figure 8: Ni and Cr elements in the cladding layer are evenly distributed in the substrate, which can play a role in solid solution strengthening and increase the hardness of the coating.

As shown in Figure 9: Using a digital microhardness tester with a load of 500g and a holding time of 12s, the microhardness of the coating of Example 3 is tested. It can be seen that the microhardness of the cladding layer is about 1.4 of Ti6Al4V. times, and there is a relatively smooth transition between the cladding layer and the substrate.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention belong to the present invention. within the scope of the technical solution of the invention.

Claims (7)

1. a titanium alloy surface anti-oxidation high-hardness wear-resistant coating is characterized in that: this coating is prepared by coaxial powder feeding laser cladding technology; Described cladding powder is recorded by mass percentage, including 75wt% TC4 and 25wt% NiCr _{- Cr3C2} powder. 2. The anti-oxidation, high-hardness, and wear-resistant coating on the surface of titanium alloy according to claim 1, characterized in that: the measured chemical composition of the TC4 powder is recorded by mass percentage, including 89.27wt% Ti, 6.22wt% Al, 4.32wt% %V, the rest are Fe, C, H, O, N. 3. The anti-oxidation, high-hardness and wear-resistant coating on the surface of titanium alloy according to claim 1, characterized in that: the measured chemical composition of the NiCr-Cr ₃ C ₂ powder is recorded by mass percentage, including 19.59wt% Ni, 10.28wt% Ni, 10.28wt% %C, the rest is Cr. 4 . The anti-oxidation, high-hardness, wear-resistant coating on the surface of titanium alloy according to claim 1 , wherein the particle size distribution of the TC4 powder is 53-150 μm. 5 . 5 . The anti-oxidation, high-hardness, wear-resistant coating on the surface of titanium alloy according to claim 1 , wherein the NiCr-Cr ₃ C ₂ mixed powder has a particle size distribution of 100-150 μm. 6 . 6. The preparation method of the titanium alloy surface anti-oxidation high-hardness wear-resistant coating according to any one of claims 1 to 5, characterized in that: comprising the following steps: S1. Test the purchased Ti6Al4V substrate and cladding powder to ensure the quality of cladding; S2. Sandblast the substrate to be clad, the surface roughness _Ra of the test block after sandblasting is about 1.98-2.07 μm; put the sandblasted test block in alcohol, carry out ultrasonic cleaning for 2-5 minutes, and then blow dry Put into a 99.9% pure argon protective box; S3. Put the cladding powder into the ball mill according to the proportion for ball milling and powder mixing. The mixing time is more than 12 hours. Put the mixed powder into a vacuum drying box, and dry it at a constant temperature of 80 °C for more than 10 hours until before the cladding process. Then take it out from the constant temperature drying box and put it into the powder feeder; S4. Use a coaxial powder feeding laser to clad the cladding powder on the test block to be clad. 7. The preparation method of the anti-oxidation, high-hardness and wear-resistant coating on titanium alloy surface as claimed in claim 6, characterized in that: the cladding parameters of S4 are specifically: a multi-pass lap rate of 50%, a laser focal length of 16 mm, and a laser focal length of 16 mm. The power is 700-1100W, the scanning speed is 0.4m/min, the powder feeding rate is 1.4r/min, the spot diameter is 3.0mm, the powder feeding gas is helium, and the gas flow rate is 7.0L/min. Argon protection, gas flow rate of 8 ~ 15L/min.

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