Introduction: Ordinary 45 steel can no longer meet the requirements for high strength, high hardness, wear resistance, corrosion resistance, and other performance characteristics. This has led to the development of surface modification technologies to improve the material surface properties. Traditional industrial cleaning methods include various types of cleaning, mostly relying on chemical agents and mechanical methods. In the context of increasingly strict environmental protection regulations in China and growing awareness of environmental and safety issues, the range of chemical agents available for industrial cleaning is becoming more limited. Therefore, it is essential to consider cleaner and non-damaging cleaning methods. Laser cleaning, characterized by its non-abrasive, non-contact, and non-thermal effects, and its suitability for a variety of materials, is considered the most reliable and effective solution. Moreover, laser cleaning can solve problems that traditional cleaning methods cannot address. Laser cladding technology has been widely adopted.

5 steel, as one of the commonly used steels in the machinery industry, has a wide range of applications. Laser surface strengthening utilizes the plasma shock waves generated by a strong laser beam to enhance the fatigue resistance, wear resistance, and corrosion resistance of metal materials. It offers several advantages, such as non-contact, no heat-affected zone, strong controllability, and significant strengthening effects. However, as technology advances, the demands for material applications continue to increase. Ordinary 45 steel can no longer meet the requirements for high strength, high hardness, wear resistance, and corrosion resistance. As a result, methods using surface modification technologies to improve material surface performance have been developed. Laser cladding, with its concentrated heat source and high efficiency, has been widely adopted in practical production. This paper investigates the effect of scanning speed on the surface structure and performance of a Ni-based composite coating prepared on the surface of 45 steel using laser cladding.

Materials and Methods: Several 200mm×100mm×6mm flat pieces of 45 steel were selected as the base material. The surface of the 45 steel to be cladded was polished with sandpaper to remove oil and rust, and then alcohol was applied to the surface. Traditional cleaning methods in the industry include various approaches, primarily relying on chemical agents and mechanical methods. As environmental protection regulations become more stringent and public awareness of environmental and safety concerns increases, the types of chemical agents available for industrial cleaning are becoming more limited. The challenge now is to find cleaner and non-damaging cleaning methods. Laser cleaning, characterized by non-abrasiveness, non-contact, and non-thermal effects, is regarded as the most reliable and effective solution. Additionally, laser cleaning can solve problems that traditional cleaning methods cannot address. The Ni35A powder was selected as the laser cladding coating powder on the GS-TFL6000A cross-flow CO2 laser generator. The main characteristics of this powder are that it contains B and Si, which provide self-deoxidizing (reducing oxygen content) and slag-forming properties. The melting temperature of the powder is between 1020-1100°C. The laser cladding was performed using a synchronous powder feeding process with nitrogen gas as the auxiliary powder-feeding gas. Under the same process conditions, the scanning speed was varied to prepare different samples, with scanning speeds set at 500, 600, and 700 mm/min.

Results and Discussion: When the scanning speed is too high, the appearance becomes more burred, and the overlap effect worsens significantly. The cladded composite coating is primarily composed of FeNi3 and Ni3B phases. The modified layer consists of the surface cladding layer, bonding zone, and substrate, with metallurgical bonding between the cladding layer and the substrate. The microhardness of the cladded layer is higher than that of the substrate, with the average hardness exceeding the substrate value, and the maximum hardness improving by 33% compared to the substrate. The best result is obtained when the scanning speed is 500 mm/min.