Original Title: Current Status and Application Development Trend of Laser Processing Technology and Industry 1 Preamble Laser is a major scientific and technological invention in the 20th century, as well as atomic energy, semiconductors and computers. It has the characteristics of high brightness, strong directivity, good monochromaticity and good coherence, and is called "the fastest knife", "the most accurate ruler" and "the brightest light". In the past 60 years, laser-related research has won many Nobel Prizes, which fully demonstrates the remarkable role of laser technology in promoting cutting-edge scientific research and promoting scientific and technological progress. The fusion of laser and related technologies forms laser manufacturing, which provides a new tool for human beings to change the world [1,2]. Laser manufacturing technology has the outstanding advantages of easy operation, non-contact, high flexibility, high efficiency, high quality, energy saving and environmental protection. It is the mainstream means of cutting, welding, surface treatment, high-performance complex component manufacturing and precision manufacturing. It is known as "universal processing tool" and "universal processing means of future manufacturing system", which has led to the development of advanced manufacturing industry. It has a profound impact on the process of industrial intelligence [1]. Laser technology is an enabling technology with strong penetrability and processability. Laser technology supports economies of scale far greater than its own. According to the 2010 American Research Report [3], the total value of telecommunications, e-commerce and information technology in the United States was $4 trillion from 2009 to 2010, of which the value of the laser itself was only $3.2 billion. Therefore, the importance of laser technology products in the economic system far exceeds the value scale of the products themselves. In recent years, China's laser processing industry has developed rapidly, and its international competitiveness has improved rapidly. Many laser enterprises have spread all over East China, South China, North China, Northeast China, Central China and Western China. According to the statistics of China Laser Industry Development Report 2019, there are 37 laser industry bases (parks) in 26 cities in China. From 2011 to 2018, the sales revenue of laser equipment increased by more than five times, and a number of laser enterprises with world competitiveness emerged [4]. After years of efforts, China's laser companies have established a solid foothold in the low-end laser industry, but there is still a big gap from the world's advanced level of high-end technology industry and high-end core components. In terms of products, follow-up products are in the majority, while original or original high-end products are relatively few. The main strength of laser technology research in China is concentrated in scientific research institutes and universities, while enterprises are relatively weak. At present, among the 30 national research platforms related to laser in China, only the National Engineering Research Center for Precision and Ultra-precision Machining and the National Research Center for Semiconductor Pumped Laser Engineering Technology remain, while the other 28 are built on the basis of scientific research institutes and universities. Universities and research institutes undertake most of the laser research projects planned by the state, while enterprises undertake only a small proportion. In the past 10 years, laser manufacturing in China has become one of the fastest growing fields in advanced manufacturing industry, forming certain characteristics, and some technologies have reached the international leading level. Laser processing equipment plays a key role in promoting the upgrading and transformation of traditional industries. A group of laser processing equipment enterprises rely on innovative processing technology and excellent equipment quality to find enough orders to grow rapidly in the new and old kinetic energy conversion market. In addition, some manufacturing companies have tasted the sweetness of upgrading and development, and are not satisfied with domestic vertical integration, but are actively exploring cross-border mergers and acquisitions of foreign high-quality laser enterprise resources, and plan to enter the field of precision processing. In the past 10 years, laser processing station has been an important antenna for equipment enterprises to provide extension services, through the development of position services, timely meet all kinds of processing needs, enhance customer viscosity. Nowadays, more and more multi-functional large-scale equipment has been developed and applied in rail transit, aerospace, shipbuilding and other industries. It is expected that by 2020, all kinds of cloud manufacturing platforms based on the industrial Internet will gradually release their value, and the laser processing station will play a greater role with the support of the cloud manufacturing platform, and will enter Southeast Asia, the Middle East, South America and other regions along the "one belt and one road". After the rapid growth from 2017 to 2018, China's laser market entered a relatively stable period in 2019. In 2019, the development of China's industrial laser market began to affect the global industrial laser business income. On the one hand, the increasingly fierce price competition has led to a sharp drop in the price of fiber lasers and ultrafast lasers, but the quality, technology and service of domestic equipment have been gradually improved in the competition, and the rise of domestic laser products is gradually replacing imported laser products; On the other hand, the application of laser technology is more cost-effective than many traditional manufacturing technologies, thus rapidly popularizing laser applications. In 2019, the total sales revenue of laser equipment (including imports) market was 65.8 billion yuan, an increase of 8.8% over 2018. Affected by the uncertain global economic trend, it is expected that the overall sales revenue of China's laser equipment market will be greatly affected in 2020 (see Figure 1). In 2019, there were more than 150 large-scale laser enterprises in China, more than half of which were concentrated in laser processing and laser-related fields [4]. Expand the full text Fig. 11 Sales Revenue and Growth Rate of China's Laser Equipment Market from 2010 to 2020E [4] The continuous emergence of new laser sources (such as blue semiconductor lasers and high-power ultrafast lasers) and new laser processing technologies (such as laser forming of metal foams and unconventional laser microprocessing) has brought excellent development prospects to the laser processing industry. The following is a brief introduction to some new lasers and laser processing technologies. 2 Fiber laser The fiber laser market in 2019 is a year of fierce competition and continued development. In 2019, the total sales of China's fiber laser market exceeded 8.26 billion yuan. From the perspective of China's fiber laser market, domestic fiber lasers have gradually realized the transformation from relying on imports to independent research and development, replacing imports to exports. With the enhancement of the comprehensive strength of domestic fiber laser enterprises and the gradual improvement of the power and performance of domestic fiber lasers, China's fiber laser market has increased from 4.07 billion yuan in 2015 to 8.26 billion yuan in 2019, and is expected to increase slightly to 8.56 billion yuan in 2020 (see Figure 2). With the continuous expansion of the fiber laser market, the domestic alternatives for the core components of fiber lasers have basically taken shape, the laser industry chain is becoming more and more mature, and the localization rate of the core components of lasers is also increasing, which makes the cost of lasers gradually decrease. The price war of lasers has also changed in stages, and the main battlefield of price competition has shifted from 1 ~ 3 kW products to 6 ~ 40 kW products. Fig. 2 China's Fiber Laser Market from 2015 to 2020E [4] 2.1 Laser cutting Laser cutting is a mature industrial processing technology with high flexibility, no contact and no stress, which can produce finished parts directly from the workpiece. Laser cutting is a very precise process with excellent dimensional stability, very small heat affected zones and narrow kerfs. In recent years, the cutting of brittle and transparent materials has provided opportunities for ultra-short pulse and ultraviolet lasers. The rapid development of China's manufacturing industry and the upgrading of traditional industrial manufacturing technology have led to the sales of complete sets of laser cutting equipment. The number of fiber lasers used in laser cutting systems has increased steadily in the past two years, and laser cutting equipment is also developing towards high power. In 2019, the demand for laser equipment in various industries is increasing. The mass production of laser equipment has led to the rapid development of medium-power laser cutting equipment, intensified the competitiveness of products, and led to lower and lower gross profit margin of medium-power cutting equipment, so laser processing manufacturers began to March into the high-power product segment. High-power laser cutting equipment is springing up on the market in 2019, and ultra-high power laser cutting machines of 12 kW, 20 kW, 30 kW and even 40 kW are already available. In 2019, China sold about 34,000 medium-power laser cutting systems and 7,000 high-power laser cutting systems. The substantial increase in power also increases the difficulty of equipment integration, which poses many challenges to upstream accessories manufacturers and system manufacturers. Some core units, such as 10000-watt cutting head, automatic focusing system, intelligent bus system and temperature control system, need to be upgraded urgently. However, domestic accessories manufacturers and system integrators have never been absent from the road of independent development, and have joined the ranks of support. 2.2 Laser welding In recent years, laser welding equipment has gradually replaced traditional welding equipment and occupied market share in hardware and building materials, automobile manufacturing, electronic products, medical equipment, new energy batteries and aerospace industries. In the automotive industry, body-in-white (BIW) welding is widely used, requiring as many as 2000 to 5000 spot welds, which are traditionally done by resistance spot welding. However, resistance spot welding of galvanized steel sheets has many problems, such as long time required for welding, high maintenance cost of electrodes, and adhesion of zinc coatings to electronic products. As the automotive industry moves toward more lightweight structures, other materials such as aluminum and magnesium alloys are becoming candidates to replace galvanized steel. Since BIW represents approximately 27% of the vehicle's weight, the use of these lightweight materials is expected to reduce the overall weight of the vehicle. For these materials, however, the problems associated with resistance spot welding are more severe. Some of these problems can be overcome by laser welding. In addition to BIW, laser welding is used in engine parts, transmission parts, alternators, solenoids, fuel injectors, fuel filters, and fuel cells. Laser welding has been used in the aerospace industry to join various superalloys, such as nickel-based alloys and titanium-based alloys. Ti6Al4V alloys are commonly used in the static and rotating components of turbine engines. In addition, the Inconel 718 is commonly used in components of aero engines and gas turbines that operate at high temperatures. Because these alloys are very expensive, welding has the potential to reduce material consumption compared to subtractive manufacturing processes. Aluminum alloys are also very popular in the aerospace industry, and in some cases, laser welding can provide a competitive advantage over other welding techniques (e.g., friction stir welding). In recent years, laser welding has been used to join polymers and plastics, as welding of dissimilar materials has become increasingly popular for reducing part cost and design flexibility. In the early days, CO2 laser was mainly used for welding of plastic parts because the laser energy was easily absorbed at its long wavelength of 10.6 mm. Most plastics are transparent at infrared wavelengths, but opaque at long wavelengths. In recent years, transmission laser welding (TLW) has emerged as a viable method for welding plastics using an internal absorber, which provides a means of absorbing heat only at the weld interface and minimizes the heat affected zone. Plastic welding equipment represented by household appliances and automotive interiors and ceramic welding equipment represented by medical devices have also become an important development direction of laser welding. After nearly 10 years of development, the domestic laser hybrid welding technology and process has made considerable progress, and has been applied in small batches in the welding of large hull components and complex curved surface components. In 2019, the handheld laser welding machine emerged. Because the access threshold of the equipment itself is not high, and it can meet the free switching of pulse welding, quasi-continuous welding and continuous welding in the use process, it is suitable for complex welds of various workpieces, ti6al4v , and there is a boom in the market. In the past two years, dozens of enterprises across the country have invested in this field. However, the patent layout of domestic enterprises in this field is obviously insufficient. The earliest patent for handheld welding equipment in China began in 2003 and came from Holywell Company in the United States. Without the support of patents, domestic industry standards in this field are basically in a "streaking" state. Low threshold indicates high competition. It is expected that in the next 2 ~ 3 years, more than half of the handheld welding equipment enterprises will withdraw from the market due to the lack of their own technological competitiveness and the exhaustion of product profits. 2.3 Laser additive manufacturing Over the past few decades, laser additive manufacturing has gained increasing attention, and lasers have become an increasingly important core of additive manufacturing (AM). Laser-based additive manufacturing systems account for more than half of the revenue of the metal additive manufacturing market, which is expected to be $774 million in 2019 and $320 million in 2024. There is no doubt that laser-based additive manufacturing has become a very important application area for the laser industry (see Figure 3). Figure 3 3 Laser Metal Additive Manufacturing One of the key requirements for using additive manufacturing, especially metal manufacturing, is to obtain the required mechanical properties. Because additive manufacturing involves many variables that can affect process conditions, attempts to determine the resulting mechanical properties by trial alone can be time consuming and expensive. To alleviate this problem and gain insight into the process, many attempts have been made to develop predictive process models. The prediction models of AM can be roughly divided into three categories: AM process thermal model, microstructure prediction model and mechanical property prediction model. Laser additive manufacturing faces enormous challenges that must be overcome in order to be accepted as an economically viable industrial manufacturing process. But at the same time, it also provides unprecedented opportunities to make new products that traditional manufacturing processes cannot. Clearly, a major challenge is to establish process-microstructure-property relationships through physics-based modeling or data-driven methods to facilitate the qualification process of additive manufacturing parts. In addition, reliable in-process monitoring methods must be developed simultaneously. The new opportunities provided by laser metal AM include the fabrication of highly customized parts (e.g. medical implants), functionally graded parts with desired local properties, topological designs for the fabrication of smart or metamaterial structures, geometrically complex parts (e.g. heat exchangers), the synthesis of novel materials, the need for people across disciplines to work together to produce new designs and materials, So as to accelerate the application of AM in manufacturing industry. 2.4 Laser Surface Texturing Laser surface texturing is a surface engineering process. The process uses a laser to create periodic microstructures on a material surface to induce desired surface properties for various applications. In laser surface texturing studies in the early 1990s, laser light was used to create patterned micropits and to investigate the effect of textured surfaces on the tribological properties of mechanical components, including mechanical seals, piston rings, and thrust bearings. Since then, with the rapid development of laser technology, the field has also developed rapidly, and a wide range of applications beyond the field of tribology have emerged. Laser surface structuring not only changes the surface morphology of materials, but also usually endows the surface with some new functions and properties, especially optical, mechanical, wettability and chemical properties. Femtosecond laser-textured silicon covered with microspikes, commonly referred to as black silicon, was one of the early discoveries showing nearly 100% absorption in the visible range, which can extend up to 2.5 mm when processed in an SF6 gas environment. Tunable reflectivity in the whole wavelength range from UV to MIR can be achieved by PS laser-induced micro/nanostructures on copper surfaces. The thermal radiation of NiTi alloy is significantly increased to about 100% by the micro-scale coral-like surface structure produced by femtosecond laser. Surface textured silicon and metals have a wide range of potential applications, including solar cells, detectors, sensors, field emission devices, plasmons, broadband heat sources and radiation heat transfer devices. Laser surface texturing has also been used to modify and control the wettability of materials. Laser surface texturing for tribological applications has been an area of interest for more than 20 years. Practice has proved that femtosecond laser textured surfaces with tens or hundreds of microns of micro-holes or micro-grooves can effectively reduce friction and wear in dry, lubricated, high temperature and high pressure processing applications. 2.5 Laser shock peening Laser shock peening (LSP) is a new shot peening technology, which introduces residual compressive stress into metal surface to improve fatigue and corrosion properties. Compared with conventional shot peening, which has been widely used in the past 60 years, laser shock peening can produce deeper plasma deformation depth and higher residual stress without leaving a rough surface. This deeper, higher compressive residual stress in turn results in a longer fatigue life. In addition, higher corrosion resistance can be provided. Laser peening technology was first discovered and studied in the early 1960s. A preliminary feasibility study of a prototype device was conducted at Battelle Laboratory in the United States. However, due to the lack of reliable, high repetition rate and high average laser power, it has not been commercialized for a long time. To mitigate foreign object damage on the leading edge of fan blades for military aircraft turbine engines, GE Aircraft Engines (Cincinnati, Ohio) developed the first commercial application in 1997. The research on laser shock peening can be divided into basic research and application research. The former is mainly related to the understanding of the basic physics in the process, while the latter is a case study of laser shock peening with different parameters and configurations, and its application to different materials. Laser shock peening (LSP) is a critical process in applications requiring increased fatigue life of engineering components. 2.6 Laser forming of metal foam Metal foam is a relatively new material that is of interest due to its high strength-to-weight ratio and excellent impact and noise absorption properties. In many engineering applications, for example, car bumpers or spacecraft components, metal foams must have a specific shape. Since the near net shape is difficult and expensive to manufacture, it is necessary to bend the metal foam into the desired shape. Bending a metal foam is not an easy task because the cell walls can only withstand low stresses and are prone to cracking. As a result, traditional mechanical bending methods can lead to cracking and cell collapse. In the past 10 years, several research groups have attempted laser shaping of metal foams and reported positive results (see Figure 4, Figure 5), but none of the studies have explored the underlying bending mechanism in sufficient detail. Future research should provide a better understanding of how laser forming affects material properties and structural attributes. Fig. 4 Laser forming of metal foam Figure 5. 5 Laser formed sample of metal foam 2.7 Laser cleaning The research and equipment development of laser cleaning technology in China started late, and the early development was basically tracking foreign technology. In the past two years, with the continuous tightening of national environmental protection policies and the increasing awareness of environmental protection, the laser cleaning industry has gradually moved towards the rising channel, and has made sustained efforts in machinery, petrochemical, road transportation, printing, electronic circuits and nuclear industries. Laser cleaning industry is still expanding its application scope, and has penetrated into the field of airline aircraft maintenance. Taking China Southern Airlines Co., Ltd. as an example, the average maintenance cost of cleaning an Airbus A320 by laser cleaning is about 400000 yuan. At present, there are no less than 30 laser cleaning enterprises with domestic sales revenue of more than 10 million yuan, and a few of them have approached the annual sales revenue of 50 million yuan. It is expected that the whole industry will break out further in 2020, with annual revenue growth expected to exceed 30%. 2.8 Ultrafast laser processing Ultra-fast laser is also the most prominent growth point in the laser market in recent years, and its growth rate is several times that of the laser industry as a whole. In 2019, there are more than 25 domestic enterprises engaged in R & D and production of ultrafast lasers, and the domestic ultrafast laser market is expected to reach 2.5 billion yuan in 2020. The ultrafast laser market has seen steady growth in the brittle materials processing market. Such as mobile phone screen special-shaped cutting, mobile phone camera sapphire cover cutting, special material marking, invisible two-dimensional code marking, high-performance FPC cutting, OLED material cutting and punching, and solar PERC battery processing and other areas of order demand. Domestic ultra-fast laser manufacturers have gradually found their own subdivision track. With the maturity of 5G communication technology, the consumer electronics market is expected to usher in a wave of switching boom in 2020. In the past two years, domestic panel manufacturers have continued to increase flexible screen production lines to provide new display solutions for the next generation of mobile phones. However, the vast majority of ultrafast lasers in the laser micro-processing equipment suitable for flexible AMOLED material processing still rely on imports. With more flexible screen production lines put into production and large-scale shipments, the huge potential market will effectively promote domestic ultra-fast laser enterprises and downstream equipment enterprises to strive for strength, thus making up for the lack of domestic equipment in the industrial chain. 2.9 Non-conventional laser micromachining Laser micromachining in water is to place the surface of the workpiece to be machined under water, and the application of water leads to the improvement of the machining quality. Waterjet guided laser micromachining, where the waterjet can help guide the laser beam, increase the working distance, reduce contamination and produce a cooling effect. Watertight assisted laser micromachining (UWLM) is a new machining technique in recent years. In addition to the watertight treatment of the surface area to be machined, UWLM also applies ultrasonic waves to cause ultrasonic cavitation and stimulate water to produce beneficial effects, such as in-situ ultrasonic cleaning, to improve the machining process. Under laboratory conditions, UWLM was found to produce much less debris deposition than laser micromachining in air with similar ns incident laser pulses, and the ablation depth per pulse was several times higher than in water without ultrasound. There is also an ultrasonic assisted machining process. Ultrasonic vibration assisted laser machining refers to the process in which the surface of the workpiece to be machined is subjected to ultrasonic vibration instead of being immersed in water. It is fundamentally different from the previously described UWLM process in that it does not involve a critical component of the ultrasonic in-water cleaning action of the UWLM around the machined area of the water-immersed workpiece surface. It has been found that the application of ultrasonic vibration can improve the efficiency of laser processing. In addition to ultrasound, attempts are being made to combine laser machining with electrochemical machining, electric or magnetic fields. Laser micromachining typically involves directing a laser light onto the surface of a workpiece to remove material. A recently improved process is known as "laser-induced plasma micromachining" (LIPMM), in which a laser-induced plasma in a medium is used as an energy source to remove material. Additionally, one way to improve the quality and efficiency of laser micromachining is to use a sequence of laser pulses, where each sequence contains two or more pulses with the appropriate pulse energy and relative timing, etc. 3 Blue Semiconductor Laser Another area of concern is the growing popularity of industrial-grade blue semiconductor lasers. Based on the growing market demand for the cutting of highly reflective materials such as copper, aluminum and their alloys, blue semiconductor lasers have been widely used in the micromachining of non-ferrous metals in recent years with low power consumption and excellent light absorption rate [5] (see Figure 6, Figure 7). The blue semiconductor laser market is also expected to achieve leapfrog development in 2 ~ 3 years, and compete with fiber lasers and red semiconductor lasers in the field of non-ferrous metal processing [4]. Figure 6 6 Blue Semiconductor Laser Fig. 7 7 Welding of copper by dual-wavelength (red and blue) semiconductor laser The price war in the past two years has accelerated the clearance of low-end production capacity in the laser processing equipment industry. In the next few years, the vicious competition of price competition will gradually evolve into the competition of talents and application solutions. The construction of high-level engineer team and service network will bring huge competitive advantages to enterprises, and constantly improving product quality and technology, shaping the multi-dimensional competitiveness of enterprises, is the key to maintain the vitality of laser processing equipment enterprises. In 2019, China added 95,81 patents related to laser technology. From the perspective of applicants, there are 5 enterprises and 5 universities in the top 10 applicants, which is different from the situation in which universities are the main R & D force in previous years [4]. For the sudden outbreak of COVID-19 at the end of 2019, although Hubei, Guangdong, Zhejiang and other provinces with good laser industry foundation suffered a certain market impact due to the disaster shutdown, the epidemic will not change the development pattern of China's laser industry in the long run. As a global manufacturing center, China has a relatively complete industrial chain foundation and broad market space, and "concentrating on major events" is an important manifestation of the advantages of the national system and the national governance system. It is believed that after the epidemic, a large number of new laser technology application scenarios will emerge by stimulating domestic demand. For example, the new infrastructure construction field represented by 5G communication, industrial Internet and big data center and the high-end industrial manufacturing field represented by aerospace and shipbuilding. 4 Looking ahead With regard to the future outlook of the laser processing industry, it mainly includes: tackling the key technologies of the core components of laser manufacturing, basically realizing the independent supply of the whole industry chain of domestic laser manufacturing; developing intelligent, extreme, high-performance advanced laser manufacturing technology and series of equipment, basically realizing the independent supply of the whole industry chain of laser manufacturing technology for high-end equipment such as aero-engines; In order to achieve large-scale industrial application, the overall strength of laser manufacturing and remanufacturing industry will reach the world advanced level. The next 30 years will be the golden 30 years for the development of China's laser processing industry. References: [1] Du Xiangwan. Research on Laser Physics and Technology [M]. Beijing : Science Press, 2018. [2] Comprehensive Group of "Research on 2035 Development Strategy of Laser Technology and Application in China". Laser Technology and Application in China Research on 2035 Development Strategy [J]. Engineering Science in China ，2020，22（3）：1-6. [3] National Academy of Sciences, National Research Council. Optics and photonics The indispensable key technology of the United States [M]. Cao Jianlin , etc. Beijing : Science Press, 2015. [4] Wuhan Documentation and Information Center, Chinese Academy of Sciences, China Laser Magazine, Chinese Optical Society. China Laser Industry Development Report 2019[R]. Wuhan Wuhan Documentation and Information Center, Chinese Academy of Sciences, China Laser Magazine, Chinese Optical Society, 2019. [5] Laserline, Germany. Product manual [Z].2019. Source: Metalworking (Hot Working), Issue 10, 2020. Author: Gu Bo, Ph. D., is an internationally renowned laser expert and entrepreneur. Founder and President of Bose Photonics. Deputy Director of deputy secretary general and Laser Processing Committee of Chinese Optical Society. Chairman of the founding meeting of China Laser Market Summit Forum. Member,titanium filler rod, Board of Directors, Laser Society of America. Chairman of the Western Photoelectric Laser Conference and Chairman of the Founding Conference on Laser 3D Printing. Visiting Professor, Massachusetts Institute of Technology. Return to Sohu to see more Responsible Editor:. yunchtitanium.com