The milling experiment utilized a YG8 cemented carbide ball-end milling cutter with a diameter of 20 mm and a thickness of 5 mm, corresponding to a tool bar dimension of Φ20×141 mm. The tool bar was fabricated from a cemented carbide rod, as illustrated in Fig. 1.

Prior to laser texturing, the rake face of the ball-end milling cutter is prepared using diamond sandpaper. This treatment enhances the surface's capacity to absorb laser energy, thereby improving the stability and quality of micro-texture formation. Additionally, it strengthens the bonding reliability between the modified layer and the underlying substrate. Subsequently, the rake face underwent ultrasonic cleaning with a 95 % ethanol solution to eliminate surface oils and contaminants, followed by natural air drying. High-purity cobalt (Co) powder served as the metallic binder, while high-purity spherical cast tungsten carbide (WC) and titanium carbide (TiC) powders, containing trace amounts of aluminum (Al), oxygen (O), and iron (Fe), acted as reinforcing phases. The powders were mixed in a mass ratio of WC : Co : TiC =78:17:5 (wt %) (Liang et al., 2021). The mixture was weighed using a precision electronic balance, dried, and then placed in a ball-mill mixer with a ball-to-powder ratio of 5:1. Milling was performed for 4 h at 200 rpm to ensure the uniform dispersion of the components.

After determining the micro-texture placement area, the mixed grinding cladding material and anhydrous ethanol were evenly applied to the rake face of the ball-end milling cutter at a powder-to-alcohol ratio of 1:0.5. The coated tool was then placed in a dry environment to facilitate the drying of the coating. Micro-textures were fabricated using a Beijing Zhengtian ZTQ-50 fiber laser marking system. The resulting micro-texture morphology is shown in Fig. 2. After processing, the surface of the textured cutter was cleaned with 95 % ethanol to remove any residual powder, followed by ultrasonic cleaning to eliminate impurities remaining in the micro-pits.

The AlCrN coating was selected as the surface coating for the cutting tool. Following the preparation of the modified texture, the AlCrN coating was deposited onto the tool surface using vacuum cathodic arc deposition technology, employing arc evaporation equipment manufactured by Oerlikon Balzers Coatings Co., Ltd.

In the experiment on modified texture preparation, a five-factor, four-level orthogonal test was designed based on the parameters of laser processing and texture. The five influencing factors included laser power (p), scanning speed (v), number of scanning passes (n), texture spacing (l), and texture diameter (d). Based on the team's previous research findings, four levels were established for each factor, leading to the formulation of the orthogonal experimental scheme, as presented in Table 1. The laser equipment utilized in the experiment had a rated power of 50 W, and the spot diameter (D) was determined by the equation D=d/2+5 (µm). Some samples were subsequently coated with AlCrN. The texture of the surface cladding layer formed by the coated cladding material is recorded as group K; the control group without coating was set up to prepare texture, which was recorded as the J group.

To account for the combined effects of laser power and spot diameter, the average energy density of the laser was calculated using Eq. (1), and the energy values for each experimental condition were summarized in Table 1. 1W‾=EN⋅S=Pf⋅S In the formula, E represents the total energy input of the textured single pit (in J), N denotes the total number of spots surrounding a single pit; S indicates the spot area (in cm²), f is the laser input frequency (in Hz), and P signifies the laser power (in W).

In this milling experiment, a VDL-1000E three-axis vertical milling machine, manufactured by Dalian Machine Tool Factory (as depicted in Fig. 3a), was employed. The Ti6Al4V workpiece measured 150 mm in length and 100 mm in width during the milling process. To mitigate the risk of premature tool failure due to damage to the tool tip and to enhance the surface quality of the machined workpiece,a jaw clamp set at a 15° angle was utilized. Based on prior experimental investigations, the machining parameters were established as follows: cutting speed (v) of 140 mm min⁻¹, cutting depth (ap) of 0.3 mm, feed rate (f) of 0.06 mm per revolution, and a milling stroke length of 150 mm per pass. During milling, horizontal milling is carried out along the length direction of the workpiece. In order to achieve green cutting and to avoid the masking effect of coolant on micro-texture friction reduction, chip storage, and cutting stability – so as to more truly reflect the role of micro-texture in interface friction and wear – lubricant is not used in this experiment (Tatsuya et al., 2009; Wu et al., 2021). A rotary dynamometer was used to capture milling force data. Each tool travels twice to collect a set of data; that is, two 150 mm trips in the length direction, and a total of 50 sets of data are collected for 100 times. To ensure data reliability and to exclude anomalies arising from machine tool vibrations and charge amplifier drift within the data acquisition system, outlier values were identified and removed during data processing. Subsequently, the milling force components along the x, y, and z axes were recorded, and the resultant force was computed and documented as a data set.

To evaluate the efficacy of the laser-cladding-based modified texture in enhancing the wear resistance of the textured coating on the ball-end milling cutter, wear measurements were conducted on the rake face of the cutter, where the modified texture was applied. Observations were made using an ultra-depth-of-field microscope, consistent with the equipment shown in Fig. 3b. Prior to examination, the rake face was cleaned with alcohol to eliminate adhered chips and contaminants. The wear area was delineated using Image Pro Plus software to identify the maximum wear region, as illustrated in Fig. 3. To enhance measurement accuracy, each tool was assessed three times at different locations within the wear area, and the mean value was calculated to represent the final wear measurement.

To investigate the influence of modified textures fabricated via laser cladding on the surface roughness of titanium alloy machined using a textured coating ball-end milling cutter, surface roughness measurements were conducted following the milling tests. The surface roughness of the titanium alloy was assessed using a TR-200 surface roughness meter, which offers a measurement accuracy of 0.001 µm. The testing apparatus is depicted in Fig. 3c. To ensure the reliability and accuracy of the results, measurements were taken at three distinct locations on the machined surface, and the average value was calculated.

To investigate the variation trend of milling forces throughout the entire cutting process, and ensure the representativeness and differentiation between data points, the average value of 10 data sets (corresponding to 20 cutting cycles) was recorded as a single data point. The milling force values in the range of 40 to 60 cutting passes were selected as the effective average values. The trend of these effective average milling forces is illustrated in Fig. 4.

As depicted in Fig. 4a, when the average laser energy density is set at 70.8 W cm⁻², the modified textured ball-end milling cutter demonstrates the lowest effective average milling force throughout the milling process. In comparison to the corresponding traditional textured ball-end milling cutter, this modified cutter exhibits the most significant reduction in effective average milling force. Moreover, relative to the traditional textured cemented carbide, the surface micro-hardness of the modified textured cemented carbide, prepared under this specific laser energy density, increases by 35 %, while the average friction force decreases by 13.1 %. This improvement is attributed to the grain refinement of the modified textured surface, which induces a fine-grain strengthening effect (Xing et al., 2024). The increase in grain boundary density effectively inhibits dislocation motion under external stress, thereby enhancing surface hardness, and improving friction and wear resistance (Zemlik et al., 2024). Consequently, during milling, the ball-end milling cutter exhibits superior wear resistance when the rake face contacts the chip, resulting in a marked reduction in the effective average milling force.

In contrast, during the preparation process of traditional textured cemented carbide surfaces, the lack of laser energy absorbed by the cladding powder leads to direct application of laser energy on the matrix surface. This interaction causes the substrate to prematurely enter the microstructural coarsening phase. Consequently, the grain size is larger, and the quantity of hard phases is lower compared to the modified textured cemented carbide surface. Therefore, at an average laser energy density of 70.8 W cm⁻², the rake face of the traditional textured ball-end milling cutter exhibits poor wear resistance, which correlates to a higher effective average milling force during the milling process.

A comparative analysis of Fig. 4a and b reveals that the effective average milling forces of both modified and traditional textured cutters decrease significantly after the deposition of the AlCrN coating. The AlCrN coating enhances surface hardness, wear resistance, and high-temperature stability by introducing aluminum into the CrN matrix. During the cutting process, the surface aluminum readily oxidizes to form a dense Al₂O₃ oxide film, which acts as a protective barrier against chemical reactions between the tool, the workpiece, and the environment (Chen et al., 2023). Furthermore, the low thermal conductivity of the coating inhibits oxygen diffusion, thereby further improving the high-temperature milling performance of the ball-end milling cutter.

Figure 5a and b demonstrate that fluctuations in the effective milling force of the modified textured cemented carbide ball-end milling cutter, irrespective of coating presence, remain minimal, indicating robust cutting stability. This stability can primarily be attributed to two factors.

First, the laser-cladding-based preparation of the modified textured surface significantly reduces the occurrence of cracks and pores, thereby minimizing transient vibrations caused by localized fractures within the recast layer during cutting. As illustrated in Fig. 6, the fine-grained carbide particles within the cladding material contribute to grain refinement strengthening of the cladding layer, resulting in a stable and reinforced microstructure. This enhancement improves both the strength and toughness of the cladding layer, effectively preventing the detachment of hard phases from the substrate and thereby increasing the overall surface stability of the tool.

Second, the deposition of the AlCrN coating facilitates the formation of a dense Al₂O₃ oxide film through the reaction of aluminum with atmospheric oxygen during frictional contact. This oxide film possesses a high melting point and exhibits excellent solid lubrication properties, characterized by a low friction coefficient. Under high-speed cutting conditions, the chip rake face maintains superior thermal resistance and efficient chip evacuation (Liu et al., 2024). The surface of the modified textured coating contains a hard phase identified as TiN_0.3. Following repeated sliding friction, localized detachment of some hard-phase particles occurs, resulting in the formation of small free hard particles. These detached particles are no longer integrated in the continuous coating structure and function as a “third body” at the tool–chip contact interface, serving roles in load bearing and isolation. Tribological investigations have demonstrated that these third-body particles can alter the nature of the interface contact through sliding, rolling, or a combination of sliding-rolling motions under conditions of high contact stress. This behavior mitigates direct sliding contact to a certain degree, thereby reducing frictional resistance at the interface. Specifically, the particles roll in conjunction with the relative sliding motion in the chip contact area (Li and Heß, 2024), effectively transforming the frictional interaction from sliding friction to rolling friction. Compared to sliding friction, rolling friction significantly reduces frictional resistance and vibration, thereby enhancing the operational stability of the modified textured coating ball-end milling cutter during machining.

The acquired vibration signals were subjected to denoising using the wavelet transform technique, followed by time-frequency analysis employing the short-time Fourier transform (STFT) (Tong and Wang, 2023). As illustrated in Fig. 7, a comparative examination of the cutting force distribution alongside the vibration time-frequency signal reveals that both the conventional textured tool and the modified textured tool exhibit pronounced nonlinear dynamic responses during machining. The time-frequency representation of the vibration signals demonstrates notable broadband characteristics accompanied by prominent high-energy peaks, indicative of substantial dispersion. Conversely, the cutting stability associated with the traditional textured coated tool displays a transitional distribution pattern overall, with the high-frequency noise in the time-frequency diagram converging. This observation suggests that the coating applied to the tool surface effectively reduces the friction coefficient at the tool–chip interface, thereby mitigating the generation of high-frequency vibrations to some extent. In comparison to the aforementioned tools, the modified textured coated tool demonstrates superior machining stability throughout the process. Specifically, the K4 group not only achieves the lowest maximum vibration energy but also exhibits a distinctly discrete narrow-band background in its spectral profile. This synergistic interaction between the highly concentrated low-modified texture and the coating facilitates a combined effect of friction reduction and vibration suppression. Consequently, it inhibits high-frequency impacts during machining, transforming the inherently nonlinear cutting process characterized by high energy and strong fluctuations into a stable machining state marked by reduced cutting forces.

The surface of conventional textured tools exhibits distinct adhesion layers and wear grooves aligned with the chip flow direction, suggesting that the predominant wear mechanism arises from the combined effects of adhesive and abrasive wear. In comparison, the modified textured surfaces demonstrate enhanced resistance to both adhesive and abrasive wear. The strength and toughness of the cladding layer are enhanced, effectively inhibiting the initiation of abrasive wear and mitigating the extent of adhesive wear. Moreover, this modification prevents the detachment of hard phases from the substrate, thereby significantly improving the overall wear resistance (Xing et al., 2024; Zhu, 2021). As demonstrated in Fig. 8a, a comparison of the rake face wear between the modified textured and traditional textured cemented carbide ball-end milling cutters indicates that the modified textured cutters exhibit significantly reduced wear. This enhancement is primarily attributed to the formation of strengthening phases, such as carbon-deficient W₂C and titanium-nitrogen compounds within the cladding layer. These phases create a pinning effect that inhibits crack propagation. Additionally, the solid solution phase (Ti,W)C_1−x contributes to a dispersion-strengthening effect, thereby enhancing the hardness of the recast layer and minimizing microstructural defects. During the wear process, the recast layer of the modified textured surface maintains point-to-surface contact with the titanium alloy workpiece, ensuring a more stable frictional process and delaying the complete wear-through of the cladding layer.

Furthermore, compared to traditional textured surfaces, the strengthened layer of the modified texture contains a higher concentration of hard phases, including TiN, Ti₂N, and (Ti,W)C_1−x. As the chip slides across the strengthening layer, these hard phases effectively reduce the material removal rate, suppress spalling and plastic deformation, and maintain surface integrity. As wear progresses, a small portion of these hard phases detaches and acts as rolling particles in the contact interface, transforming sliding friction into rolling friction. This transition leads to a decreased friction coefficient and extends the durability of the strengthening layer. In contrast, the strengthening layer of the traditional textured ball-end milling cutter has lower hardness and reduced hard-phase content, resulting in premature wear and early exposure of the tool substrate, which subsequently contacts the chip. The modified textured tool, due to its higher hard-phase content, delays the onset of wear-induced shedding and prolongs the functional lifespan of the strengthening layer, thereby postponing substrate exposure. Consequently, under equivalent cutting durations, the cumulative wear observed in traditional textured tools is significantly greater than that in modified textured tools.

As shown in Fig. 8b, both the modified and traditional textured ball-end milling cutters demonstrate further reductions in rake face wear after the deposition of the AlCrN coating. This enhancement is attributed to the formation of a dense composite oxide layer consisting of Al₂O₃ and Cr₂O₃ at elevated temperatures, resulting from the interaction between aluminum and chromium elements. The composite oxide film exhibits excellent wear resistance, oxidation resistance, and chemical stability, effectively preventing tool–chip reactions and reducing heat diffusion into the substrate. Consequently, the coating significantly enhances the overall wear resistance of the tool. Additionally, the modified textured coating surface exhibits a higher density of molten spatters and fine, hard particles, which act as nucleation cores during the deposition of AlCrN. These nucleation sites facilitate grain refinement, leading to smaller grain sizes and a denser microstructure of the coating. The refined and compact structure of the coating further enhances the adhesion strength and wear resistance at the tool–chip interface, thereby improving the durability and stability of the modified textured coated ball-end milling cutter.

Figure 9a compares the machined surface roughness of cemented carbide modified textured and traditional textured ball-end milling cutters after milling titanium alloy. The results indicate that the surface roughness achieved with the modified textured ball-end milling cutter is significantly lower than that of the traditional textured cutter. This enhancement can be attributed to the higher micro-hardness and the increased presence of hard phases on the surface of the modified textured tool. Its superior wear resistance effectively mitigates the wear-induced passivation of the cutting edge during machining, thereby preserving a sharp cutting edge profile, and reducing both cutting vibration and material adhesion. Under identical cutting durations, the modified textured ball-end milling cutter demonstrates enhanced cutting performance, which contributes positively to the improvement of the machined surface roughness of the titanium alloy.

Research has demonstrated that during the milling of titanium alloys, cutting vibrations constitute a significant factor influencing the surface roughness of the machined workpiece. Moreover, fluctuations in the effective value of the cutting force have been identified as a primary cause of variations in cutting vibration. In this study, the cutting force signal is utilized as an indirect indicator to assess the trend of cutting vibrations, thereby obviating the need for accelerometers, other vibration sensors, or direct measurement of vibration amplitude (Wang et al., 2022). Experimental results reveal that at average laser energy densities of 70.8 and 75.2 W cm⁻², the effective average milling force of the modified textured ball-end milling cutter exhibits minimal fluctuation with respect to the number of cutting cycles, indicating a stable cutting process. However, an increase in the average laser energy density to 108.3 W cm⁻² results in more significant fluctuations in the effective mean milling force, leading to a marked increase in the machined surface roughness of the titanium alloy. Under the same conditions (70.8 W cm⁻²), the traditional textured ball-end milling cutter displays similar instability.

Figure 9b compares the machined surface roughness of cemented carbide modified textured and traditional textured coated ball-end milling cutters used for milling titanium alloys. It is observed that the machined surface roughness of both types of milling cutters is reduced. This improvement is attributed to the deposited coating, which significantly enhances the surface adhesion of the tool, minimizes the adhesion between the workpiece material and the tool surface, and mitigates the formation of the built-up edge. The built-up edge tends to detach periodically during machining and re-enter the cutting zone, causing scratches and scales on the machined surface. Therefore, coating deposition effectively contributes to enhancing the surface finish of titanium alloys.

Furthermore, the matrix grain size of the modified textured tool is slightly reduced, and the coating deposited on this fine-grained substrate exhibits increased internal stress and enhanced interfacial bonding strength, thereby improving the elastic modulus of the coating. Meanwhile, the surface roughness of the modified texture, fabricated by laser cladding, is optimized, which further strengthens the coating adhesion. An analysis of the coating H/E ratio (hardness-to-elastic modulus ratio) reveals that the modified textured coating shows a noticeable improvement compared to the traditional textured coating. A higher H/E ratio corresponds to better fracture toughness, greater resistance to plastic deformation, and effective inhibition of crack propagation. The synergistic effect of high hardness and low elastic modulus enables the coating to better resist wear and plastic deformation (Shanmugasundar et al., 2024). This index serves as an important indicator of coating wear resistance, further enhancing the surface performance of the ball-end milling cutter and facilitating the machining of titanium alloy surfaces with lower surface roughness.