CN102560411A - Preparation method of anti-ablative coating on surface of titanium alloy - Google Patents

Abstract

A method for preparing an anti-ablation coating on the surface of a titanium alloy belongs to the field of material corrosion and protection. Using the chemical reaction WF ₆ +3H ₂ →W+6HF, the refractory metal tungsten coating is obtained on the surface of the titanium alloy. The preparation method of the anti-ablation coating on the surface of titanium alloy is characterized in that: the chemical reaction temperature is 420-480°C, the flow rate of _H2 is 3.2-3.8L/min, the flow rate of _WF6 is 5.2-5.8g/min, and the heating rate is 8 ～12℃/min, the cooling rate is 10～15℃/min, and the chemical reaction time is 25～35min. By controlling the chemical reaction temperature, gas flow rate, heating and cooling speed and other parameters, a tungsten coating with good ablation resistance can be obtained. The coating is tested in a constant temperature furnace at 1000 ° C, and the effect is obvious.

Description

A kind of preparation method of anti-ablation coating on titanium alloy surface

technical field

The invention belongs to the field of metal material corrosion and protection, and in particular provides a preparation method of an ablation-resistant refractory metal tungsten protective coating for titanium alloys.

Background technique

Titanium is a structural metal developed in the 1950s. Titanium alloys have the characteristics of high specific strength, toughness and corrosion resistance, and are widely used in aerospace, military, construction, automobile and other industries. However, the oxidation resistance and corrosion resistance at high temperature are not ideal, and it is easy to ablate. Surface treatment can effectively improve the performance of titanium alloys. Traditional surface modification treatments such as carburizing, boronizing and nitriding have disadvantages such as long treatment cycle and workpiece variability; coatings prepared by thermal spraying technology have shortcomings such as loose structure and weak bonding with the substrate; laser Beam and electron beam surface modification are rarely used due to complex equipment and high cost. The refractory metal tungsten has a very high melting point (3410°C), has strong wear resistance and corrosion resistance, and has stable chemical properties at high temperatures. This patent uses the chemical reaction of the gas to obtain a refractory metal tungsten coating on the surface of the titanium alloy substrate. The coating has strong anti-ablation performance at high temperatures.

Contents of the invention

The invention adopts the chemical reaction between gases to form a refractory metal tungsten coating with a thickness of 8-12 microns on the titanium alloy substrate. The chemical reaction equation is: WF ₆ +3H ₂ →W+6HF.

The equipment used includes: temperature control cabinet (requires high temperature control accuracy); heating furnace (with a workpiece placement device inside and a smooth gas circulation pipe); tail gas absorption device (using sodium hydroxide aqueous solution to spray and absorb the tail gas, meet environmental protection requirements).

Process flow:

(1) Pretreatment of workpiece surface.

Use alkaline water to wash away the dirt on the surface of the workpiece, rinse it with water, and then use acetone and alcohol to perform ultrasonic cleaning respectively to obtain a clean surface.

(2) The workpiece is put into the furnace.

(3) Exhaust the air in the device through high-purity Ar, and check the airtightness of the device.

(4) Stop flowing Ar, start flowing H ₂ , and heat.

(5) Chemical reaction.

After reaching the set temperature, pass WF ₆ to carry out the gas chemical reaction, and at the same time open the tail gas absorption device to absorb the reaction by-product HF. According to different requirements, different thickness coatings can be obtained on the surface of titanium alloy.

The chemical reaction temperature is 420-480°C, the flow rate of H ₂ is 3.2-3.8L/min, the flow rate of WF ₆ is 5.2-5.8g/min, the heating rate is 8-12°C/min, and the cooling rate is 10-15°C/min. The chemical reaction time is 25-35 minutes.

(6) cooling.

After the reaction is over, turn off the WF ₆ gas, and continue to pass H ₂ until room temperature. Baked, tested.

Main features of this patented technology

(1) The operation of this patent is simple, the whole process is automatically controlled, and it is easy to realize industrial mass production;

(2) This patent adopts the chemical reaction under normal pressure, and equipment is simple, and input is few, and quick effect is obtained.

(3) This patent is suitable for titanium alloys of various shapes and sizes, and has wide applicability;

(4) The composition of the coating obtained in this patent is 100% tungsten, which has an obvious high-temperature protection effect on titanium alloys.

Description of drawings:

Figure 1: Metallographic micrograph of titanium alloy with tungsten coating.

Detailed ways:

After the surface pretreatment of the titanium alloy substrate, the process parameters and effects of the chemical reaction are as follows:

By setting appropriate chemical reaction parameters, a refractory metal dense tungsten coating of 8 to 10 microns is formed on the titanium alloy substrate, which can protect the titanium alloy very well, and the ablation resistance temperature is increased by more than 400°C. The process parameters are set as follows: chemical reaction temperature 420-480°C, H ₂ flow rate 3.2-3.8L/min, WF ₆ flow rate 5.2-5.8g/min, heating rate 8-12°C/min, cooling rate 10 ~15°C/min, reaction time 25~35min.

Claims (1)

1. the preparation method of the anti-ablative coating of titanium alloy surface is characterized in that: 420～480 ℃ of chemical reaction temperature, H ₂Flow is 3.2～3.8L/min, WF ₆Flow is 5.2～5.8g/min, and heat-up rate is 8～12 ℃/min, and cooling rate is 10～15 ℃/min, and chemical time is 25～35min.

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