3. Development Trend of Arc Additive Manufacturing 3.1 Application of Arc Additive Manufacturing in Tin-Based Babbitt Bearing Bushes The tin-based babbitt alloy of the bearing bush still does not exceed 200 t, so additive manufacturing has great potential and social benefits in the field of bearing bush. At present, except for several leading enterprises in the domestic bearing bush field that have actively introduced additive manufacturing technology to replace the casting process and achieved practical results, most small and medium-sized enterprises are still observing and hesitating due to their large one-time investment and concerns about the reliability of the technology. With the continuous improvement of high reliability requirements of downstream enterprises, large and medium-sized and flat bearing bushes will gradually concentrate on enterprises with additive manufacturing technology. Although centrifugal casting has many shortcomings, as a mature technology and has the characteristics of fast casting, it will still play a role in the manufacture of small-sized and large-scale bearing bushes that do not require high bonding strength. Brazing as a bearing repair technology will still be popular in the industry, but compared with MIG welding technology, automatic brazing technology requires the use of flux to manufacture bearing pads, and the additive process needs to maintain a higher temperature of the matrix, and the advantage of bonding strength is not obvious. It may become the mainstream technology, and Morgan Oil Film Bearing (Shanghai) Co., Ltd., the first domestic company to adopt brazing technology, has switched to TIG welding technology instead of brazing technology. The spraying process is more complicated than MIG welding and TIG welding, and the advantage of bonding strength is not obvious, so it does not have the basis for large-scale technology promotion. Laser cladding additive technology has low efficiency and high cost, and does not have a practical basis. In the field of bearing bush manufacturing using tin-based babbitt as anti-friction material, it is difficult to change the trend that additive manufacturing will replace casting technology. Although the TIG welding technology can obtain a better additive layer (a layer of tin-based babbitt alloy is surfacing on the tile back), the low speed of surfacing and the slightly inferior bonding strength restrict its development and promotion; MIG welding While the technology has many advantages, it suffers from additive process spatter. The emergence of the high-speed servo wire feeding technology of the new digital MIG welding technology solves the problem of spatter caused by the vaporization and explosion of the droplet, and further improves the speed of surfacing welding. Literature [31] pointed out that my country has made breakthroughs in laser-arc hybrid technology. When used in stainless steel and other welded joints, its performance is equivalent to TIG welding, and the welding efficiency is increased by 5 times. It has been widely used in major national equipment. If this technology can be applied in the field of bearing bush manufacturing, it will play an important role in the manufacture of high-quality and high-reliability sliding bearings in my country. To sum up, with the development of various equipment, especially in response to the requirements of localization of major equipment, the bearing bush will inevitably develop towards high efficiency, high precision, high technology content, high reliability, long life and EHS friendly, arc Additive technology is in line with this development trend and will be widely used in the industry. 3.2 The composition of tin-based babbitt alloy The research on the composition of tin-based babbitt alloy is carried out on the basis of high reliability, mainly focusing on improving bonding strength, refining grains, reducing segregation, and improving high temperature creep resistance, wear resistance and resistance. Oxidation, etc. expand. Cd-based soldering materials can improve wettability, improve welding performance, reduce alloy melting point, and improve alloy fluidity, but its severe toxicity is strictly limited in the field of soldering; As plays a role in refining the structure, but its Toxicity is also concerned by the industry; Zn can improve the creep resistance at high temperature, but Zn is an easily oxidized metal, and the formed alloy has poor wettability, and the casting process affects the bonding strength, so it is difficult to be widely used in casting production; Short carbon fibers and carbon nanotubes, as reinforcing materials for tin-based babbitt alloys, have no practical application prospects. The arc additive process is protected by argon gas, so there is no need to add antioxidant elements to the tin-based babbitt alloy. At the same time, the thickness of the cladding layer is thin, the cooling rate is fast, and the structure is refined, and there is no need to add elements to refine the structure. The high-temperature molten pool and argon protection in the material process do not need to add elements that improve wettability and reduce the melting point of the alloy; therefore, the trend of tin-based babbitt composition optimization is mainly based on Sn, Sb, and Cu as the matrix, and the addition can improve the resistance. Abrasive elements (such as Ni) and elements that improve high temperature creep resistance (such as Ag, Zn). The addition of Ni, Ag, Zn and other elements will be industrialized and practical in tin-based babbitt alloys. As and Cd are only used in special industries. Other improved elements added should consider factors such as industrialization difficulty, environmental protection, cost and wire processing. . 3.3 Supporting testing technology Bearing casting technology has formed a relatively complete testing and evaluation standard system after nearly a hundred years of development.