## 2 Experimental and Calculation Details  
YG6 cemented carbides (\(\omega_{\text{WC}}\) = 94%, \(\omega_{\text{Co}}\) = 6%, density of 14.6-15.0 g.cm\({}^{-2}\), thermal conductivity of 75.55 W\(\cdot\)m\({}^{-1}\cdot\)K\({}^{-1}\), hardness(HRA) of 89.5, bending strength of 1.42 GPa) 10 mm \(\times\) 10 mm \(\times\) 3 mm in dimension were used as substrates and high-quality diamond films were deposited on the substrates through a bias-enhanced hot filament chemical vapor deposition system. The deposition condition of the diamond films is listed in Table 1. The surface morphologies of CVD diamond coating are depicted in Figure 1. It is visible from Figure 1a that the average grain size of a diamond crystal, of approximately 100 nm, is smaller than the size of normal diamond particles, suggesting that the obtained diamond grains in the coating are nanoscale. The average surface roughness of the original as-grown surface derived from topography is measured at 0.342 \(\upmu\)m, and the cross profile shows a homogeneous morphology of the coating surface (see Figure 1b). The applied fs laser pulses of 100 fs duration generated by a Ti: Sapphire laser system (America, Coherent), operating at the wavelength of 800 nm, an 8 \(\times\) objective, which can provide a beam waist diameter of 30 \(\upmu\)m measured at the 1/e intensity, was used to perform the ablation experiments. The schematic drawing of the laser processing setup is depicted in Figure 1c. The fs laser beam propagates from the laser source to the objective lens by mirrors and is vertically irradiated on the diamond coating surface in the ambient air. The ablation results of diamond coating essentially rely on two parameters of the femtosecond laser, i.e., single-pulse energy, \(E\), which directly determines the \begin{table}
\begin{tabular}{c c} \hline \hline
**Conditions** & **Deposition Parameters** \\ \hline Flow of Acetone/Hydrogen & 30/300 sccm \\ Pressure & 5 kPa \\ The voltage of Tantalum wire & 20 V \\ Bias current & 2 A \\ Distance between Tantalum wire and substrate & 9–10 mm \\ Deposition temperature & 450 \({}^{\circ}\)C \\ The time of deposition & 3 h \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Preparation conditions of CVD diamond film. Figure 1: Experimental materials and schemes. (**a**) Surface SEM photograph of the diamond coating; (**b**) three-dimensional topography and section profile(orange curve) of the coating; (**c**) schematic of the adopted femtosecond laser processing system; and (**d**) three experimental schemes, namely, changing the number of pulses \(N\) only, changing the single pulse energy \(E\) only, and changing both \(N\) and \(E\). value of laser fluence, and the effective number of pulses, \(N\), which contributes to the incubation effect. In this work, we investigated the influence of three fs laser conditions on the ablation results. The three conditions are as follows: Changing \(E_{\text{P}}\) and \(N\) separately and changing both the two parameters at the same time, as illustrated in Figure 1d. In the case of continuous scanning, the laser focus point will overlap with each other, so it is more appropriate to investigate the influence of the number of accumulated pulses per unit area, i.e., the effective number of pulses, on the ablation results than to simply consider the influence of repetition rates. The effective number of pulses, \(N\), can be calculated by Equation (1):  
\[N=k\cdot\frac{2\omega_{0}f}{v}, \tag{1}\]  
where \(k\) is the number of scanning times (all experiments in this work are single scanning, thus \(k=1\)), \(\omega_{0}\) is the beam waist,\(f\) is the repetition rate, \(v\) is the scanning speed. Therefore, the effective number of pulses can be adjusted by controlling the repetition rate or scanning speed. The scanning speed and direction can be controlled by the 3-axis translation stage with a position accuracy of 0.1 \(\upmu\)m. The single pulse energy is regulated by the attenuator.