TA19 alloy surface cyclic heating boronizing method

Abstract

The invention discloses a TA19 alloy surface cyclic heating boronizing method. The method comprises the following steps that TA19 titanium alloy to be boronized is subjected to surface pretreatment; the TA19 titanium alloy subjected to surface treatment is placed in a corundum burning boat and embedded with a boronizing agent, then a gap between a burning boat cover of the corundum burning boat and the burning boat is sealed with refractory glue, and the corundum burning boat is placed in a ventilated place to be dried; placing the treated corundum burning boat in a tubular furnace, vacuumizing to 3 * 10 <-3 >-5 * 10 <-3 > MPa, then carrying out circulating heat treatment, and cooling along with the furnace after the circulating heat treatment to obtain the TA19 alloy with a boriding layer on the surface; wherein the number of times of the cyclic heating period is 1-6. According to the method, rapid growth of a boriding layer can be achieved, the heat preservation time above the beta phase transformation point is shortened, and coarsening of a TA19 alloy matrix structure is slowed down. In addition, the thickness of the boriding layer can be adjusted by changing the heat preservation time in the heating period.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of surface modification, more particularly to a TA19 alloy surface cyclic heating boronizing method. BACKGROUND

[0002] TA19 titanium alloy (Ti-6Al-2Sn-4Zr-2Mo-0.1Si, wt.%) as a near-alpha titanium alloy has high strength, high toughness, good creep resistance, and a service temperature of about 500℃, which can be used for automobile engine valves, etc., not only reducing weight and prolonging service life, but also having high reliability and saving fuel. However, in addition to heat resistance, exhaust valves also require high wear resistance. Titanium alloy has poor wear resistance, and when used as a moving part, it is prone to adhesive wear, resulting in workpiece seizure. Therefore, when TA19 titanium alloy is used as an exhaust valve, its surface must be modified.

[0003] Solid powder boronizing surface modification has the advantages of simple process equipment, convenient and flexible operation, easy adjustment of boronizing agent formula, and easy cleaning of workpieces after boronizing, and is one of the important technologies for improving the surface properties of titanium and its alloys. By boronizing the surface of titanium alloy, a double-phase boronizing layer structure of TiB2 outer layer + TiB whisker inner layer is formed, the hardness of the TiB2 outer layer can reach 3000HV-3800HV, and the hardness of the TiB whisker can reach 800HV-1500HV, so the hardness of the boronized titanium alloy is significantly improved, and the wear resistance is correspondingly improved.

[0004] Patent CN101608296A discloses a method for boronizing the surface of titanium alloy, which uses a single-component boronizing agent B4C. In the boronizing process of TC4 alloy as the substrate, the carburizing temperature is higher than the β transition temperature of TC4 alloy by about 100℃, and needs to be maintained at a higher boronizing temperature of 1100℃ for a long time of 20h to obtain a boronizing layer of 10-15μm, which easily leads to the coarsening of the substrate structure and the weakening of the mechanical properties of the substrate. SUMMARY

[0005] The present application aims to overcome the above-mentioned defects in the prior art and provide a TA19 alloy surface cyclic heating boronizing method.

[0006] To achieve the above-mentioned purpose, the technical solution of the present application is as follows:

[0007] A TA19 alloy surface cyclic heating boronizing method, comprising the following steps:

[0008] Step 1: surface pretreatment of the TA19 titanium alloy to be boronized to obtain a TA19 titanium alloy after surface pretreatment;

[0009] Step two: the surface treated TA19 titanium alloy is placed in a corundum boat, and is embedded with boronizing agent, and then the gap between the boat cover and the boat is sealed with refractory glue, and is placed in a ventilated place for drying;

[0010] Step three: the corundum boat treated in step two is placed in a tube furnace, and is vacuumed to 3×10 -3 ~ 5×10 - 3 MPa, and then is subjected to cyclic heat treatment, and is cooled in the furnace after the cyclic heat treatment, to obtain a TA19 alloy with a boronized layer on the surface;

[0011] The cyclic heat treatment comprises:

[0012] first heating to 1030~1040℃ for 0.5h~4h, and then cooling to 950~1000℃ for 0.5h~4h, as a heating cycle, and the number of cyclic heating cycles is 1~6.

[0013] Optionally, in step one, the surface pretreatment comprises the following steps: the TA19 titanium alloy to be boronized is cut by wire cutting to obtain a sample with a size of 10mm×10mm×2mm, and then the surface is polished with 180#, 400#, 1200# and 2400# sandpaper, and then is ultrasonically cleaned with deionized water for 3min~7min, and is dried with an electric hair dryer.

[0014] Optionally, in step two, the drying time is 22h~24h.

[0015] Optionally, in step two, the embedded TA19 titanium alloy is placed vertically in the corundum boat.

[0016] Optionally, in step two, the boronizing agent comprises the following components by weight percentage: 30wt.%~45wt.% of B4C powder, 30wt.%~40wt.% of SiC powder and 20wt.%~40wt.% of graphite powder.

[0017] Optionally, the particle size of the B4C powder is 0.5μm~20μm; the particle size of the SiC powder is 1μm~50μm; and the particle size of the graphite powder is 1μm~10μm.

[0018] Optionally, the cyclic heat treatment comprises: first heating to 1030~1040℃ at a heating rate of 10℃ / min~20℃ / min for 0.5h~4h, and then cooling to 950~1000℃ at a cooling rate of 5℃ / min~20℃ / min for 0.5h~4h, as a heating cycle, and the number of cyclic heating cycles is 1~6.

[0019] Optionally, the thickness of the boronizing layer is 8-13 μm.

[0020] The embodiment of the present application has the following advantages:

[0021] The present application discloses a TA19 alloy surface cyclic heating boronizing method, which comprises the following steps: heating to 1030-1040 ℃ and keeping for 0.5-4 h, then cooling to 950-1000 ℃ and keeping for 0.5-4 h, as a cycle of heating period, the rapid growth of the boronizing layer can be realized by the alternate heating and keeping mode, the keeping time above the β phase transition point is shortened, and the coarsening of the TA19 alloy matrix structure is slowed down. In addition, the thickness of the boronizing layer can be adjusted by changing the keeping time in the cycle. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The XRD pattern of the boronizing layer of the present application comparative example 1.

[0023] Figure 2 The cross-section morphology of the boronizing layer of the present application comparative example 1.

[0024] Figure 3 The XRD pattern of the boronizing layer of the present application example 1.

[0025] Figure 4 The cross-section morphology of the boronizing layer of the present application example 1.

[0026] Figure 5 The XRD pattern of the boronizing layer of the present application example 2.

[0027] Figure 6 The cross-section morphology of the boronizing layer of the present application example 2.

[0028] Figure 7 The XRD pattern of the boronizing layer of the present application example 3.

[0029] Figure 8 The cross-section morphology of the boronizing layer of the present application example 3.

[0030] Figure 9 The XRD pattern of the boronizing layer of the present application example 4.

[0031] Figure 10 The cross-section morphology of the boronizing layer of the present application example 4. DETAILED DESCRIPTION

[0032] The present application will be further described in conjunction with specific embodiments, but the present application is not limited in any way by the embodiments.

[0033] Comparative example 1

[0034] A surface cyclic heating boronizing method of TA19 alloy is disclosed in the present comparative example, comprising the following steps:

[0035] Step one: the TA19 titanium alloy to be boronized is cut by wire cutting to obtain a sample with a size of 10 mm x 10 mm x 2 mm, then the surface thereof is polished by 180#, 400#, 1200# and 2400# sandpaper respectively, and then the sample is ultrasonic cleaned with deionized water for 5 min and dried by an electric hair dryer to obtain the TA19 titanium alloy after surface pretreatment.

[0036] Step two: the TA19 titanium alloy after surface treatment is placed in a corundum boat in a vertical manner, and is embedded with a boronizing agent, then the gap between the boat cover and the boat of the corundum boat is sealed with refractory glue, and is placed in a ventilated place to dry for 24 h. The boronizing agent comprises the following components by weight percentage: 40wt.% of B4C powder, 35wt.% of SiC powder and 25wt.% of graphite powder.

[0037] Step three: the corundum boat treated in step two is placed in a tube furnace, and is vacuumed to 3 x 10 -3 MPa, and then is subjected to cyclic heat treatment, and is cooled in the furnace after the cyclic heat treatment to obtain the TA19 alloy with a boronized layer on the surface; wherein the cyclic heat treatment comprises: firstly heating to 1040℃ at a heating rate of 10℃ / min and keeping for 6h, and then cooling to room temperature, and taking out the boat. As shown in Figure 1 , the boronized layer is composed of TiB2, TiC and TiB phases. As shown in Figure 2 , the total thickness of the boronized layer is measured to be 10.26±0.75μm.

[0038] Example 1

[0039] A surface cyclic heating boronizing method of TA19 alloy is disclosed in the present example, comprising the following steps:

[0040] Step one: the TA19 titanium alloy to be boronized is cut by wire cutting to obtain a sample with a size of 10 mm x 10 mm x 2 mm, then the surface thereof is polished by 180#, 400#, 1200# and 2400# sandpaper respectively, and then the sample is ultrasonic cleaned with deionized water for 5 min and dried by an electric hair dryer to obtain the TA19 titanium alloy after surface pretreatment.

[0041] Step two: the TA19 titanium alloy after surface treatment is placed in a corundum boat in a vertical manner, and is embedded with a boronizing agent, then the gap between the boat cover and the boat of the corundum boat is sealed with refractory glue, and is placed in a ventilated place to dry for 24 h. The boronizing agent comprises the following components by weight percentage: 40wt.% of B4C powder, 35wt.% of SiC powder and 25wt.% of graphite powder.

[0042] Step three: the corundum boat obtained by step two is placed in a tube furnace, vacuumed to 3x10 -3 MPa, and then subjected to cyclic heat treatment. After the cyclic heat treatment, the furnace is cooled to obtain a TA19 alloy with a boronized layer on the surface; wherein the cyclic heat treatment comprises: first heating to 1040℃ at a heating rate of 10℃ / min for 3h, and then cooling to 1000℃ at a cooling rate of 20℃ / min for 3h as a heating cycle, the number of cyclic heating cycles is 1, and finally the furnace is cooled to room temperature, and the boat is taken out. As shown in Figure 3 , the boronized layer is composed of TiB2, TiC and TiB phases. As shown in Figure 4 , the total thickness of the boronized layer is measured to be 10.96±0.78μm, which is thicker than that of the boronized layer of the comparative example 1.

[0043] Example 2

[0044] The present embodiment discloses a cyclic heating boronizing method for a TA19 alloy surface, comprising the following steps:

[0045] Step one: the TA19 titanium alloy to be boronized is cut by wire cutting to obtain a sample with a size of 10mmx10mmx2mm, and then the surface is polished with 180#, 400#, 1200# and 2400# sandpaper, respectively. After that, it is ultrasonically cleaned with deionized water for 5min and dried with an electric hair dryer to obtain the TA19 titanium alloy after surface pretreatment.

[0046] Step two: the TA19 titanium alloy after surface treatment is placed in a corundum boat in a vertical manner, and is embedded with a boronizing agent, and then the gap between the boat cover and the boat of the corundum boat is sealed with refractory glue, and is dried for 24h in a ventilated place. The boronizing agent comprises the following components by weight percentage: 40wt.% of B4C powder, 35wt.% of SiC powder and 25wt.% of graphite powder.

[0047] Step three: the corundum boat obtained by step two is placed in a tube furnace, vacuumed to 3x10 -3 MPa, and then subjected to cyclic heat treatment. After the cyclic heat treatment, the furnace is cooled to obtain a TA19 alloy with a boronized layer on the surface; wherein the cyclic heat treatment comprises: first heating to 1040℃ at a heating rate of 10℃ / min for 3h, and then cooling to 1000℃ at a cooling rate of 20℃ / min for 3h as a heating cycle, the number of cyclic heating cycles is 1, and finally the furnace is cooled to room temperature, and the boat is taken out. As shown in Figure 5 , the boronized layer is composed of TiB2, TiC and TiB phases. As shown inFigure 6 As shown in FIG. 3, the total thickness of the boronized layer is 11.42±1.69 μm, which is greater than the thickness of the boronized layer of Comparative Example 1 and Example 1.

[0048] Example 3

[0049] The present example discloses a method for cyclically heating boronizing a TA19 alloy surface, comprising the following steps:

[0050] Step one: the TA19 titanium alloy to be boronized is cut by wire cutting to obtain a sample with a size of 10 mm x 10 mm x 2 mm, and then the surface thereof is polished with 180#, 400#, 1200# and 2400# sandpaper, respectively, and then ultrasonic cleaned with deionized water for 5 min and dried with an electric hair dryer to obtain the TA19 titanium alloy after surface pretreatment.

[0051] Step two: the TA19 titanium alloy after surface treatment is placed in a corundum boat in a vertical manner, and is embedded with a boronizing agent, and then the gap between the boat cover and the boat of the corundum boat is sealed with refractory glue, and is dried for 24 h in a ventilated place. The boronizing agent comprises the following components by weight percentage: 40 wt.% of B4C powder, 35 wt.% of SiC powder and 25 wt.% of graphite powder.

[0052] Step three: the corundum boat treated in step two is placed in a tube furnace, and is vacuumed to 3 x 10 -3 MPa, and then is subjected to cyclic heat treatment, and is cooled in the furnace after the cyclic heat treatment to obtain a TA19 alloy with a boronized layer on the surface; wherein the cyclic heat treatment comprises: first heating to 1040℃ at a heating rate of 10℃ / min and maintaining for 0.5 h, and then cooling to 1000℃ at a cooling rate of 20℃ / min and maintaining for 0.5 h, which is one heating cycle, and the number of cyclic heating cycles is 6. Finally, the boat is taken out after cooling to room temperature in the furnace. As shown in FIG. 4, the boronized layer is composed of TiB2, TiC and TiB phases. As shown in FIG. 5, the total thickness of the boronized layer is 12.21±1.88 μm, which is greater than the thickness of the boronized layer of Comparative Example 1 and Examples 1-2. Figure 7 Figure 8

[0053] Example 4

[0054] The present example discloses a method for cyclically heating boronizing a TA19 alloy surface, comprising the following steps:

[0055] ​​Step one: the TA19 titanium alloy to be boronized was cut by wire cutting to obtain a sample with a size of 10 mm x 10 mm x 2 mm, and then the surface of the sample was polished with 180#, 400#, 1200# and 2400# sandpaper respectively, and then ultrasonic cleaned with deionized water for 5 min, and dried with an electric hair dryer to obtain the TA19 titanium alloy after surface pretreatment.

[0056] Step two: the TA19 titanium alloy after surface treatment was placed in a corundum boat in a vertical manner, and was embedded with a boronizing agent, and then the gap between the boat cover and the boat of the corundum boat was sealed with refractory glue, and was dried for 24 h in a ventilated place. The boronizing agent comprises the following components by weight percentage: 45wt.% of B4C powder, 30wt.% of SiC powder and 25wt.% of graphite powder.

[0057] Step three: the corundum boat treated in step two was placed in a tube furnace, and was vacuumed to 3 x 10 -3 MPa, and then was subjected to cyclic heat treatment, and was cooled in the furnace after the cyclic heat treatment to obtain the TA19 alloy with a boronized layer on the surface; wherein the cyclic heat treatment comprises: first heating to 1040℃ at a heating rate of 10℃ / min for 0.5h, and then cooling to 1000℃ at a cooling rate of 20℃ / min for 0.5h, as one heating cycle, and the number of cyclic heating cycles is 6. Finally, the boat was taken out after cooling to room temperature. As shown in Figure 7 , the boronized layer is composed of TiB2, TiC and TiB phases. As shown in Figure 8 , the total thickness of the boronized layer is measured to be 12.42±1.66μm.

[0058] The above embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A method of surface cyclic heating boronizing of TA19 alloy, characterized in that, The method comprises the following steps: Step one: surface pretreatment of TA19 titanium alloy to be boronized to obtain TA19 titanium alloy after surface pretreatment; Step two: placing the TA19 titanium alloy after surface treatment in a corundum boat, embedding with a boronizing agent, then sealing the gap between the boat cover and the boat of the corundum boat with refractory glue, and drying in a ventilated place; Step three: the corundum boat treated in step two is placed in a tube furnace, vacuumed to 3x10 -3 ~5x10 -3 MPa, and then subjected to cyclic heat treatment, and after the cyclic heat treatment, the TA19 alloy with a boronized layer on the surface is obtained by furnace cooling. The cyclic heat treatment comprises: First heating to 1030-1040℃ for 0.5-4h, then cooling to 950-1000℃ for 0.5-4h, which is one heating cycle, and the number of cyclic heating cycles is 1-6.

2. The TA19 alloy surface cyclically heated boronizing process of claim 1 wherein, In step one, the surface pretreatment comprises the following steps: The TA19 titanium alloy to be boronized is cut by wire cutting to obtain a sample with a size of 10mm*10mm*2mm, then the surface is polished with 180#, 400#, 1200# and 2400# sandpaper, and then ultrasonic cleaning with deionized water for 3-7min, and blow-drying with an electric hair dryer.

3. The TA19 alloy surface cyclically heated boronizing process of claim 1 wherein, In step two, the drying time is 22-24h.

4. The TA19 alloy surface cyclically heated boronizing process of claim 1 wherein, In step two, the embedded TA19 titanium alloy is placed vertically in the corundum boat.

5. The TA19 alloy surface cyclically heated boronizing process of claim 1 wherein, The boronizing agent comprises the following components by weight percentage: 30-45wt.% B4C powder, 30-40wt.% SiC powder and 20-40wt.% graphite powder.

6. The TA19 alloy surface cyclically heated boronizing process of claim 5 wherein, The particle size of the B4C powder is 0.5-20μm; The particle size of the SiC powder is 1-50μm; The particle size of the graphite powder is 1-10μm.

7. The TA19 alloy surface cyclically heated boronizing process of claim 1 wherein, The cyclic heat treatment comprises: first heating to 1030-1040℃ at a heating rate of 10-20℃ / min for 0.5-4h, then cooling to 950-1000℃ at a cooling rate of 5-20℃ / min for 0.5-4h, which is one heating cycle, and the number of cyclic heating cycles is 1-6.

8. The TA19 alloy surface cyclically heated boronizing process of claim 1 wherein, The thickness of the boronized layer is 8-13μm.

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