We propose an effective method to control the local hardness and morphology of a metal surface by tilting the incident angle of a horn during ultrasonic nanocrystal surface modification (UNSM). In this study, surface treatment using UNSM was performed on an S45C specimen and a parameter study was conducted for optimization. The process parameters were the feeding rate, static load, striking force, and processing angle (Ф). In particular, the Ф was analyzed by tilting the horn by 0°, 10°, 20°, 30°, 40°, and 45° to understand its effect on surface hardness and changes in the morphology. From fundamental experiments, some important phenomena were observed, such as grain-microstructure changes along the processing and thickness directions. Furthermore, to verify the practical usefulness of this study, a flat and a hemispherical specimen of S45C material were treated using UNSM with various values of Ф. A significant change in hardness (an increase from 2–45%) and a gradual hardness gradient on the tested specimens could be easily realized by the proposed method. Therefore, we believe that the method is effective for controlling the mechanical hardness of a metal surface.

我们提出了一种有效的方法，通过在超声纳米晶体表面改性（UNSM）过程中倾斜角的入射角来控制金属表面的局部硬度和形态。在这项研究中，使用UNSM对S45C标本进行了表面处理，并进行了参数研究以优化。工艺参数是进料速度，静载荷，冲击力和加工角度（Ф）。特别是Ф通过将焊头倾斜0°，10°，20°，30°，40°和45°进行分析，以了解其对表面硬度和形态变化的影响。通过基础实验，观察到一些重要现象，例如沿加工和厚度方向的晶粒微观结构变化。此外，为了验证这项研究的实用性，我们使用UNSM对S45C材料的扁平和半球形样品进行了处理，并采用了各种Ф值。所提出的方法可以很容易地实现硬度的显着变化（从2–45％增加）和被测样品的逐渐硬度梯度。因此，我们认为该方法对于控制金属表面的机械硬度是有效的。