CN110528010A - A kind of nickel base superalloy fracture cleaning method - Google Patents

Abstract

A method for cleaning a fracture of a nickel-based superalloy, comprising the following steps: step 1) preparing a cleaning solution; step 2) completely immersing the alloy fracture in the cleaning solution, and boiling in a water bath to obtain a preliminary cleaned fracture; step 3) Paste the fracture repeatedly with adhesive tape until the tape no longer sticks dirt; step 4) scrub the fracture with a brush soaked in acetone solution; step 5) completely immerse the fracture in HCl solution, and perform ultrasonic cleaning; step 6) repeat step 3) and step 4); step 7) using the fracture as the cathode, and the platinum electrode as the anode, and electrolytic cleaning in HCl solution; step 8) repeating step 3) and step 4), until it is enlarged by 500 times to 1000 times under the scanning electron microscope, The dirt on the fracture is cleaned, and the characteristics of the fracture can be identified. The invention can effectively clean the oxides on the fracture of the nickel-based high-temperature alloy, avoid secondary damage to the fracture, and make sample preparation preparations for finding the real cause of alloy failure in service.

Description

A kind of fracture cleaning method of nickel base superalloy

technical field

The invention belongs to the field of general inhibition of corrosion or fouling of metal materials in the metallurgical industry, and in particular relates to a method for cleaning fractures of nickel-based superalloy materials.

Background technique

Nickel-based superalloys (for example, grades GH6783, GH2984, GH3625) have been widely used in the manufacture of steam pressure valve bolts in ultra-supercritical power units in recent years, which are affected by external environments such as vibration, high temperature around 650 ° C, and water vapor. Generally, fracture failure occurs between 20,000 and 50,000 hours of service.

The fracture faithfully records the irreversible deformation of the material before fracture under load and the environment, as well as the whole process of crack initiation and propagation until fracture, which is the most important physical evidence for fracture failure analysis. At present, the commonly used fracture cleaning methods for steel parts with short service time mainly include: (1) Organic solvent cleaning method, such as soaking or scrubbing with gasoline, acetone, alcohol, etc., which is suitable for cleaning the grease and other pollution attached to the fracture surface (2) Ultrasonic method, using an ultrasonic cleaning machine for ultrasonic cleaning, which is suitable for cleaning off loose attachments attached to the surface; (3) dry air flow or soft brush, which is suitable for removing loose particles attached to the surface; ( 4) Chemical etching method, the chemical etching solution is prepared by a variety of reagents, which is suitable for removing denser oxides, the production process is relatively complicated, and there is often the risk of overwashing damage to the fracture morphology due to excessive chemical reactions; (5) ) electrochemical cleaning method, usually using an inert anode (such as carbon and platinum), using the fracture sample to be cleaned as a cathode, and the hydrogen bubbles generated on this sample mechanically remove surface waste and deposits, for example, Ni The electrolyte solution for fracture electrolysis of -Cr-based superalloys is mostly composed of alkali and salt (see literature for details: Lu YL, Brooks CR, Chen LJ, etal. A technique for the removal of oxides from the fracture surfaces of alloy[J].Materials characterization,2005,54(2):149-155.), this electrolyte is generally used to remove grease and silicate scale on the fracture surface.

Due to the corrosion of the environmental conditions of the special working conditions of the power plant (for example, humid atmosphere, corrosive gas/liquid environment, etc.) and the long service time, it is difficult to obtain timely protection for the fracture on site and rust occurs, so that the surface of the fractured fracture is usually covered with oxidation Products, corrosion products, and deposits. If such coverings are not cleaned properly, it will not be possible to obtain an objective and accurate electron microscopic appearance of the fracture. However, the above-mentioned existing methods are not ideal for the fracture cleaning effect of superalloy parts with a long service time, or the oxides and corrosion products on the fracture surface cannot be removed and the fracture morphology cannot be revealed, or the local excessive cleaning leads to damage. Real fracture texture information.

Contents of the invention

In order to overcome the deficiencies in the above-mentioned prior art, the invention provides a method for cleaning the fracture of a nickel-based superalloy, the specific steps are as follows:

Step 1) preparing cleaning solution;

Step 2) completely immersing the fracture of the nickel-based superalloy to be cleaned in the cleaning solution, and boiling in a water bath to obtain a preliminary cleaned fracture;

Step 3) Paste the fracture repeatedly with tape until the tape no longer sticks dirt;

Step 4) Scrub the fracture with a hairbrush soaked in acetone solution;

Step 5) completely immerse the fracture in HCl solution, and perform ultrasonic cleaning;

Step 6) repeat step 3) and step 4);

Step 7) The fracture is used as the cathode, and the platinum electrode is used as the anode, and electrolytic cleaning is carried out in the HCl solution. The components of the HCl solution are: 18-22 parts of HCl and 78-82 parts of _H2O , The electrolysis time is 1-5min;

Step 8) Repeat step 3) and step 4) until the dirt on the fracture is cleaned and the characteristics of the fracture can be identified when the magnification is 500 to 1000 times under the scanning electron microscope.

Further, in the step 1), the cleaning solution consists of the following components in parts by weight: 14-18 parts of NaOH, 4-8 parts of KMnO ₄ and 74-82 parts of H ₂ O.

Further, the boiling time in the water bath in the step 2) is 100-140min.

Further, in the step 5), the HCl solution consists of the following components in parts by weight: 18-22 parts of HCl and 78-82 parts of H ₂ O.

Further, in the step 5), the ultrasonic cleaning time is 1-5 minutes.

Further, in the step 7), during electrolytic cleaning, the current density is 50-150A/m ² , and the electrolysis temperature is 30-50°C.

Compared with prior art, the beneficial effect of the present invention is:

1. The preparation of the cleaning solution is simple and easy to obtain: the reagents used in the cleaning solution are all commonly used reagents, no special purchase is required, and there is no long-term toxicity, which poses less threat to the health of users.

2. After boiling in a water bath, tape the fracture several times and scrub the fracture with acetone solution to remove Ni oxides; then remove Fe oxides on the surface of the fracture by pickling; Electrolyte with Ni-Cr-based superalloy fracture electrolysis Compared with mostly alkali plus salt, the electrolytic solution of the present invention is HCl solution, which not only has the effect of pickling, but also generates more hydrogen in the process of electrolysis, and physically impacts the remaining oxidation products, greatly reducing the impact on the long-term Damage to the fracture texture of stress corrosion and stress fatigue under long-term service conditions, and the fracture morphology is preserved to the greatest extent.

3. This method avoids the secondary damage to the fracture due to improper cleaning, prepares samples for finding the real cause of the fracture of the alloy, and provides an important basis for judging the failure mode and prevention of the material. It is in the actual product failure identification and The design and precautions of experimental products have important implications.

The above description is only an overview of the technical solutions of the present invention. In order to understand the technical means of the present invention more clearly and implement them according to the contents of the description, the preferred embodiments of the present invention and accompanying drawings are described in detail below. The specific embodiment of the present invention is given in detail by the following examples and accompanying drawings.

Description of drawings

Fig. 1 is a block diagram of the steps of the cleaning method of the present invention;

Fig. 2 is the schematic diagram of the fracture morphology processed by the prior art (NaOH ₊ KMnO water bath boiling with oxalic acid and acetone ultrasonic cleaning respectively);

Figure 3 is an uncleaned oxidation fracture;

Fig. 4 is the cleaning result of adopting method of the present invention to oxidation fracture (Fig. 3);

Figure 5 is an uncleaned fresh non-oxidized fracture;

Fig. 6 is the cleaning result of the fresh unoxidized fracture (Fig. 5) using the method of the present invention.

Detailed ways

The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1-2 cleans the fracture of the GH6783 nickel-based superalloy that has been in service for 23,000 hours. Example 3 cleans the fracture of the fresh unoxidized GH6783 nickel-based superalloy.

Figure 2 shows the nickel-based superalloy fracture after being boiled in a NaOH+KMnO ₄ water bath and ultrasonically cleaned with oxalic acid and acetone respectively. It can be seen from the figure that the oxides on the surface of the fracture have been relaxed, but most of the subsurface oxides still remain, and the fracture characteristics are still is heavily covered.

Example 1

The specific steps for cleaning the fracture of the GH6783 nickel-based superalloy that has been in service for 23,000 hours:

Step 1) Prepare a cleaning solution by mixing 15 parts of NaOH, 5 parts of KMnO ₄ and 80 parts of H ₂ O in parts by weight;

Step 2) Submerge the fracture of the GH6783 alloy completely in the above-mentioned cleaning solution, boil in a water bath, obtain a preliminary cleaned fracture after 130 minutes, and blow dry;

Step 3) Paste the fracture repeatedly with tape until the tape no longer sticks dirt;

Step 4) Scrub the fracture with a hairbrush soaked in acetone solution;

Step 5) Place the fracture completely in an HCl solution of 19 parts by weight of HCl and 81 parts of H ₂ O, and perform ultrasonic cleaning for 4 minutes.

Step 6) Tape the fracture repeatedly until the tape no longer sticks to the dirt, and scrub the fracture with a brush soaked in acetone solution.

Step 7) Using the fracture as the cathode and the platinum electrode as the anode, perform electrolytic cleaning for 4 minutes in an HCl solution of 19 parts of HCl and 81 parts of H ₂ O with a current density of 120A/m ² and an electrolysis temperature of 42°C.

Step 8) Paste the fracture repeatedly with adhesive tape until the tape no longer sticks to the dirt, and brush the fracture with a brush soaked in acetone solution until the dirt on the fracture is cleaned when it is magnified by 500 times to 1000 times under the scanning electron microscope , to identify fracture characteristics.

The steps and operating methods of Examples 2 and 3 are the same as those of Example 1. See Table 1 for the specific cleaning solution, electrolyte ratio, water bath boiling time, and electrolysis conditions.

The cleaning method of table 1 embodiment 1-3

Comparison of fracture morphology before and after cleaning,

Example 2 Referring to accompanying drawing 3 (before cleaning) and accompanying drawing 4 (after cleaning), it can be seen that the method of the present invention can completely remove the oxides on the surface of the fracture, and rarely damage the fracture morphology, and the cleaning effect is good.

Embodiment 3 Referring to accompanying drawing 5 (before cleaning) and accompanying drawing 6 (after cleaning), comparison shows that the fracture tissue of material before and after cleaning does not find serious corrosion marks, and the dimple tissue feature in the fracture is clear, thus it can be seen that the present invention The above method will not damage or change the fracture morphology when the fracture is not oxidized for a long time, and the cleaning effect is better, which is helpful for fracture analysis.

In the present invention, the adhesion between the surface oxide and the substrate is firstly reduced by alkali boiling, followed by repeated pasting and brushing to mechanically remove the oxide of Ni in the outer layer, and then the oxide of Fe on the surface of the fracture is removed by pickling, and then the oxide of Fe on the surface of the fracture is removed by HCl cathode. The electrolysis method removes the remaining oxides on the surface under the continuous flushing of acidic solution and cathode gas. Compared with pure pickling, the gas shock generated by electrolysis has a more obvious effect on the shedding of oxides. In practice, it has been found that if the percentage of HCl is too high, the hydrogen ions in the electrolyte increase, the pH value decreases, the conductivity increases, the electrolysis current increases, the electrolysis process is too fast, and the substrate is easily corroded. The percentage of HCl is too low to clean the oxides. The high temperature of the electrolyte will increase the conductivity of the electrolyte and consume a lot of heat energy, and the solution will evaporate in large quantities, deteriorating the working environment. After comprehensive consideration, the electrolysis time is 1-5min, the current density is 50-150A/m ² , and the electrolysis temperature is 30-50℃

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Any equivalent replacement or change of the inventive concepts thereof shall fall within the protection scope of the present invention.

Claims (6)

1. a kind of nickel base superalloy fracture cleaning method, which comprises the following steps:

Step 1) prepares cleaning solution；

Nickel base superalloy fracture to be cleaned is totally submerged and is placed in cleaning solution by step 2), carries out water-bath and boils, obtains The fracture tentatively cleaned；

Step 3) pastes fracture with adhesive tape repeatedly, until the no longer viscous lower foul of adhesive tape；

Step 4) the hairbrush scrub fracture for being soaked with acetone soln；

Fracture is completely immersed in HCl solution by step 5), is cleaned by ultrasonic；

Step 6) repeats step 3) and step 4)；

For step 7) using fracture as cathode, platinum electrode makees anode, and electrolytic cleaned is carried out in HCl solution, according to parts by weight, institute State the component of HCl solution are as follows: 18-22 parts of HCl and H₂O78-82 parts, electrolysis time 1-5min；

Step 8) repeats step 3) and step 4), until when amplifying 500 times to 1000 times under scanning electron microscope, on the fracture Foul cleans up, and can distinguish Fracture Characteristics.

2. a kind of nickel base superalloy fracture cleaning method according to claim 1, it is characterised in that: the step 1) In, the cleaning solution is made up of according to parts by weight: 14-18 parts of NaOH, KMnO₄4-8 parts and H₂74-82 parts of O.

3. a kind of nickel base superalloy fracture cleaning method according to claim 2, it is characterised in that: in the step 2) The time that water-bath is boiled is 100-140min.

4. a kind of nickel base superalloy fracture cleaning method according to claim 1, it is characterised in that: the step 5) In, the HCl solution is made up of according to parts by weight: 18-22 parts of HCl and H₂78-82 parts of O.

5. a kind of nickel base superalloy fracture cleaning method according to claim 4, it is characterised in that: the step 5) In, the ultrasonic cleaning time is 1-5 minutes.

6. a kind of nickel base superalloy fracture cleaning method according to claim 5, it is characterised in that: the step 7) In, when electrolytic cleaned, current density 50-150A/m², electrolysis temperature is 30-50 DEG C.