## 2 Fabrication Method and Experiments
### Fabrication Materials  
The end-face-structured CBN grinding wheel prepared by ultrasonic-assisted laser cladding technology is divided into two parts: a printing layer and a matrix. The printing layer is composed of CBN grain and a copper-based binder. The purpose of fabricating a structured grinding wheel using ultrasonic-assisted laser cladding technology is to achieve chemical metallurgical bonding between the printing layer and the matrix. Compared with the traditional grinding wheel manufacturing method, it improves the holding force of the binder on the abrasive particles. The method of structuring is changed to reduce the thermal stress in the manufacturing process. The residual stress of the printed part is reduced and the grinding performance of the grinding wheel is enhanced.  
The selection of abrasive particles must first consider their strength, particle size, crystal type, and surface conditions. Next, it is necessary to consider the oxidation of abrasive particles under the action of a laser heat source. The hardness of CBN is second only to diamond, and the thermal stability is stronger than diamond. The wear resistance is four times that of traditional abrasives, while having good thermal conductivity. Therefore, in this study, the Funnike CBN-980T abrasive particle (Funik Superhard material Co., Ltd., Zhengzhou, China) was selected; its surface was plated with titanium, and the particle size was 100-120 mesh.  
In the process of laser cladding, in order to ensure that the binder can be uniformly and completely covered on the matrix, it is necessary to make a reasonable choice of matrix materials and properties. The matrix needs to have sufficient strength to avoid cracking and crushing during grinding due to the high-speed rotation of the grinding wheel. In addition, considering the economy of the selected base material, 45 steel was finally determined as the matrix material for the ultrasonic-vibration-assisted laser cladding for preparing the grinding wheel.  
If the melting point of the metal bond is too low, it will affect its bonding strength with the grinding wheel matrix, resulting in the CBN particle falling off during grinding. This will not only affect the grinding effect, but also reduce the service life of the grinding wheel. If the melting point of the bond is too high, it will make the grinding wheel formation process difficult to control. The metal bond should also have good wettability for the CBN particles [24] to fully fill the gap between the CBN abrasive particles and the 45 steel abrasive wheel matrix, and improve the holding power of the abrasive particles. Due to the nature of CBN particles, they are difficult to wet using ordinary metal materials, and materials containing active elements are usually used as grinding wheel bonds. At the same time, the strength and hardness of the binder should meet the subsequent grinding requirements [25]. To prevent the rapid wear of the bond layer in the grinding process and extend the service life of the grinding wheel, in this study, spherical Cu-Sn-Ti alloy was  
Figure 1: The laser cladding system.  
selected as the binder with a particle size of \(-100\)\(-\)\(+\)250 mesh. The mass fraction of each element is shown in Table 2.