Laser repair of thrust bearing pads first removes the Babbitt alloy casting layer on the surface of the original thrust pad, and then uses laser cladding technology to re-clad a defect-free and high-bonding Babbitt alloy layer on the surface of the steel billet. The surface of the repaired parts is well formed, the grain structure is dense, and the grains are fine. The performance has exceeded the performance of the original new products and can meet the usage requirements.

Thrust tile introduction

The thrust shoe is a key piece of equipment for the safe operation of a vertical hydro-generator unit, and its health directly affects the sliding characteristics of the thrust bearing. The mirror plate and the thrust tile cooperate to form a structural component that is lubricated by dynamic pressure oil film bears axial load, and plays the role of bearing the weight and water thrust of the rotating part of the entire unit. The Babbitt alloy coating of the thrust pad is cast, which is prone to defects such as pores, lack of fusion, and shelling. Huirui invented a process that uses laser cladding technology to re-clad a layer of Babbit alloy layer on the surface of the steel billet that is defect-free and has high bonding strength. The surface of the thrust tile parts after laser repair is well formed, the grain structure is dense, and the grains are fine. The performance has exceeded the performance of the original new product, which can greatly extend the service life of the thrust tile.

Introduction to Babbitt Alloy

Babbitt alloy was invented by American Babbitt, also known as white alloy. The main components of Babbitt alloy are tin, lead, antimony, and copper. Antimony and copper are used to improve the strength and hardness of the alloy. Because of its good wear resistance, thermal conductivity, and special organizational structure, it is beneficial to reduce friction, so it is widely used in spindle bearings and bushings of large machinery. Babbitt is the most widely known bearing material and its use dates back to the Industrial Revolution.

The laser cladding equipment independently developed and manufactured by Huirui, as well as the supporting process technology, can effectively prepare Babbitt alloy, and its performance is better than traditional process methods such as casting and welding, achieving an almost ideal process state, and is a Babbitt alloy shaft. Lining direct molding and partial repair provide new perfect solutions.

Structural characteristics of babbitt alloy:

• Hard phase particles are evenly distributed on the soft phase matrix;
• The soft phase matrix makes Babbitt alloy have very good embedding, compliance, and anti-seizure properties;
• After running-in, the soft phase matrix is concave and the hard points are convex, forming a small gap between the sliding surfaces, which becomes an oil storage space and lubricating oil channel, which is beneficial to friction reduction, and the convex hard points play a supporting role. Conducive to carrying;

Disadvantages of common processing methods of babbitt alloy:

Babbitt alloys are mainly divided into two categories: tin-based Babbitt alloys and lead-based Babbitt alloys.

Tin-based Babbitt alloy is the most widely used tin-antimony-copper-ternary alloy. Its representative alloy brands are ZSnSb4Cu4, ZSnSb8Cu4, and ZSnSb11Cu6.

The strength and hardness of lead-based Babbitt alloy is lower than that of tin-based Babbitt alloy, and its corrosion resistance is also poorer, but its economy is better than that of tin-based Babbitt alloy. Its commonly used brands include ZPbSb16Sn16Cu2, ZPbSb16Sn1As1, ZPbSb10Sn6, etc.

Casting is a commonly used processing method for Babbitt alloy. By cleaning the base plate, tin-laying, smelting, casting, and cooling of babbitt alloy, the bearing bush with bearing lining can be obtained on the base plate. After years of development, the casting process has become very mature. However, due to the characteristics of the process principle itself, the following problems still exist:

• The molding process is complicated, difficult to control, and the quality is unstable;
• Poor binding force, prone to shelling defects;
• The tissue is thick and prone to defects such as shrinkage holes and blisters;
• Component segregation and poor performance uniformity;
• The production process is highly dependent on people and the working environment is poor. ‍

Laser cladding technology (Laser Cladding) uses a laser as a heat source. Under the irradiation of the laser beam, the cladding powder (metal, ceramic powder, etc.) and the surface of the substrate is rapidly heated and melted. After the beam is removed, it is self-cooling. Manufacturing method. Compared with traditional additive technology, laser cladding technology has the following characteristics:

• Applicable to a wide range of material systems, laser cladding can be performed on various metals and ceramic materials;
• Coating material components can be selected and designed based on performance requirements;
• The coating dilution rate is low and can maintain the excellent performance of the original material;
• The coating structure is fine and dense, and is metallurgically bonded to the base material;
• The coating thickness has a wide adjustable range and is easy to control, and the process is flexible and easy to automate;
• Local processing of selected areas can be performed;

Using laser cladding technology to process and shape Babbitt alloy can completely solve the problem of Babbitt alloy shelling. Babbitt alloy has a fine structure and excellent performance. Through systematic research, Huirui has mastered the key technology of laser cladding Babbitt alloy, with a one-time molding pass rate of 100%, and has been successfully applied in the industry, with stable and reliable performance.

Practical examples of Babbitt alloy

(1) Tin-based Babbitt alloy application case 1

The tile parts in the picture below are key equipment for the safe operation of power generation equipment. Due to the large area of the workpiece, shrinkage, and shrinkage cavities are prone to defects during the casting process. After long-term use, they are worn and thinned, and shrinkage and cavities are easily exposed to the workpiece. surface, resulting in increased friction, which may cause tile burning and shutdown. In order to eliminate the above-hidden dangers, avoid major economic losses, improve its use stability and quality, and extend its service life, our company remanufactured its tiles with laser cladding and prepared an alloy layer on the surface of the steel billet.

After repair, it was detected by relevant technical means that the Babbitt alloy has a dense structure, excellent and stable performance, is 100% combined with the steel billet, and is metallurgically bonded, successfully restoring and improving the performance of the workpiece.