Effects of TiC Addition on Mechanical Behavior and Cutting Performance of Powder Extrusion Printed Cemented Carbides

Abstract

This study addresses the limited research on the mechanical behavior and cutting performance of additive manufactured cemented carbides with high TiC content, which has impeded the rapid development of additive manufacturing in carbide cutting tools. Using powder extrusion printing (PEP) additive manufacturing technology, we successfully fabricated WC-10TiC-12Co and WC-20TiC-12Co carbides with a relative density exceeding 97%. We investigated the effects of TiC content on the mechanical properties and cutting performance of WC-12Co carbide tools. The results show that TiC addition significantly affects the mechanical properties and cutting performance of PEP-processed carbides. Adding 10 wt.% and 20 wt.% TiC increases the Vickers hardness to 1403 HV30 and 1496 HV30, respectively, compared to 1317 HV30 for WC-12Co without TiC. However, TiC addition reduces the flexural strength from 2025 MPa for WC-12Co to 1434 MPa with 10 wt.% TiC and further to 915 MPa with 20 wt.% TiC. Tribological testing indicates that TiC addition reduces the friction coefficient and enhances wear resistance. HT250 cutting tests reveal that TiC addition significantly improves wear resistance and reduces workpiece surface roughness, particularly during longer cutting durations. This study broadens the scope of carbide materials suitable for PEP additive manufacturing.

1. Introduction

Cemented carbide, as a metal-ceramic composite tooling material, offers superior properties compared to other tooling materials. It exhibits high compressive strength, excellent wear resistance, exceptional hardness, a high elastic modulus, strong impact resistance, good vibration damping performance, corrosion resistance, and dimensional stability [1]. These outstanding mechanical properties have led to its widespread use in cutting tool manufacturing [2]. Extensive research has been conducted on traditional WC-Co cemented carbides, showing that adjusting the Co content in WC-Co alloys can precisely manipulate microstructure and therefore the mechanical properties [3,4]. Additionally, incorporating Ti(C,N) additives or modifying the Ti content in WC-Ti-Co systems improves mechanical performance by promoting grain refinement and suppressing abnormal grain growth, ultimately enhancing tool wear resistance [5,6,7,8,9]. However, as technological demands advance, traditional powder metallurgy faces increasing challenges in forming complex parts and structures, limiting the further development and application of cemented carbide tools.

Additive manufacturing (AM) enables the production of complex structural components, offering a viable solution to the limitations of traditional powder metallurgy in creating intricate geometries. For WC-Co cemented carbides, two main AM process routes exist: thermal-based powder bed fusion (PBF) and cold-forming-based forming-debinding-sintering (FDS) [10,11]. PBF technologies, such as selective laser melting (SLM) and selective electron beam melting (SEBM), often encounter challenges related to heterogeneous WC grain growth and low relative density in cemented carbide samples [12,13,14,15]. In WC-Co cemented carbides with cobalt content between 9–25 wt.%, the combination of a steep thermal gradient, rapid cooling, and a high liquid-phase proportion significantly constrains dimensional contraction during sintering. This leads to low relative density, increased porosity, and heterogeneous WC grain growth. In contrast, FDS, which includes debinding and sintering as post-processing steps, operates at a stable forming temperature, with prolonged sintering durations and complete material melting. These attributes enhance densification and eliminate internal porosity, resulting in cemented carbides with high relative density [16,17,18,19].

Among cold-forming technologies, two widely used methods are binder jetting (BJ or 3DP) and powder extrusion printing (PEP). The BJ process typically utilizes granulated powders, which can introduce significant interparticle porosity during powder spreading. This porosity may cause WC abnormal grain growth and inhomogeneous microstructure during sintering [20,21,22]. In contrast, PEP employs micron-, submicron-, or even nano-sized WC and Co powders, significantly improving the sintering activity, densification efficacy, and microstructural homogeneity. In recent years, extrusion-based additive manufacturing has made significant progress in a growing range of materials, including ceramic and metal powders, demonstrating significant application potentials in aerospace, mechanical processing, and cutting tool industries [23,24,25,26,27,28]. Chen et al. systematically investigated PEP fabrication of WC-9 wt.%Co cemented carbides through optimized feedstock powder design and printing parameters [29]. Their methodology achieved near-full density with homogeneous microstructural characteristics, yielding mechanical properties comparable to conventional powder metallurgy counterparts. Zhao et al. developed a paraffin/polymer binder system for WC-8 wt.%Co systems, revealing critical atmosphere-dependent sintering mechanisms [30]. Subsequent work advanced this through an optimization of the organic binder system, demonstrating that polyvinyl butyral (PVB) content governs green part strength [31].

While PEP processing has emerged as an important additive manufacturing (AM) technique for cemented carbides, current research remains predominantly confined to the WC-Co system. This persistent focus on such limited compositions substantially limits both the expansion of processable carbide systems and the broader technological implementation of PEP-based AM. Crucially, little systematic studies have been reported yet regarding PEP fabrication of TiC-modified WC-Co carbides—a critical research gap given TiC’s established role in enhancing high-temperature performance and wear resistance. To address this technological bottleneck, we present the comprehensive investigation of WC-xTiC-12Co composites fabricated through PEP, systematically varying TiC content from 0 to 20 wt.% while maintaining a constant 12 wt.% Co binder phase. The carbides underwent a two-step debinding process followed by sinter-hip to produce the final cemented carbide components. The study systematically examined the effect of TiC content on the microstructure and key mechanical properties of PEP-fabricated cemented carbides. Additionally, the cutting performance of the PEP processed cemented carbide tools was evaluated.

2. Materials and Methods

2.1. Materials

The WC and Co powders used in this study, with similar average particle sizes of 1 μm, were supplied by Xiamen Golden Egret Special Alloy Co., Ltd. (Xiamen, China) (Figure 1a,b). The TiC powder, with an average particle size of 1 μm, was supplied by Shanghai Shuitian Materials Technology Co., Ltd. (Shanghai, China) (Figure 1c).

2.2. PEP and Post-Processes

Figure 2 schematically demonstrates the whole PEP processing, including feedstock powder mixing (Figure 2a), kneading and printing (Figure 2b), and debinding and sintering (Figure 2c). The WC, TiC, and Co powders were mixed via ball milling according to the compositions listed in

Table 1. Composition of WC-xTiC-12Co.

Sample	WC-12Co	WC-10TiC-12Co	WC-20TiC-12Co
WC (wt.%)	88	78	68
TiC (wt.%)	0	10	20
Co (wt.%)	12	12	12

. The ball milling was processed in a horizontal ball mill for 8 h with anhydrous ethanol as the milling medium. Carbide milling balls with 8 mm diameter were employed to improve the milling efficiency. The powder-ball weight ratio was set at 1:1. Upon ball milling, the carbide slurries were then thoroughly dried to obtain the cemented carbide powder mixtures (Figure 2a). Then the dried carbide powder mixtures were kneaded into carbide pellets with 2 mm diameter and 3 mm length before PEP processing was performed.

The kneading process was conducted by adding a thermoplastic binder to the dried carbide mixtures using an Open-Close Type Internal Mixer (UP-M0300 experimental mixer, Shenzhen Shenghua 3D Technology Co., Ltd., Shenzhen, China) at 165 °C and 30 r/min for 2 h. A volume fraction of 51% was set for the carbide phase. A paraffin-based thermoplastic organic binder synthesized in-house was employed. The carbide pellets were fed to a PEP equipment (Shenzhen Shenghua 3D Technology Co., Ltd.) for printing process. The precision limitations of the PEP equipment may somewhat affect the dimensional accuracy of the printed carbide parts but do not significantly impact the research outcomes. Cemented carbide tools and test specimens were designed in 3D modeling software (UG, 10.0, Siemens PLM Software, Plano, TX, USA), exported as STL files, and imported into the printer software. The key PEP processing parameters, including layer thickness, printing speed, and nozzle temperature are listed in

Table 2. Main PEP processing parameters in this study.

Nozzle Temperature (°C)	Build Plate Temperature (°C)	Printing Speed (mm/s)	Layer Thickness (mm)	Layer Thickness (mm)	Flow Rate (%)
165	90	10	0.2	0.6	85

. After printing, the base plate of the printer was cooled to room temperature before the green parts were detached for further debinding and sintering (Figure 2b).

A two-step debinding process was applied to the printed green bodies [32]. First, the green bodies were immersed in n-heptane for solvent debinding (35 °C, 4 h). After drying, they underwent secondary debinding in a tubular furnace under a combined argon and vacuum atmosphere. The temperature was raised from room temperature to 200 °C at 5 °C/min, held for 1 h, then increased to 450 °C at the same rate for another 1 h, and finally heated to 600 °C and held for 1 h. As the binder decomposed, eliminating the bonding bridges between powder particles, the debond parts exhibited low strength and became prone to structural damage during handling. To address this issue, the samples were presintered by heating from 600 °C to 1000 °C under vacuum (0.1 Pa) at 5 °C/min for 1 h. This induced partial solid-state sintering, enhancing the strength of the debond parts. The temperature curve for the thermal debinding and presintering processes is shown in Figure 3a. Finally, the debond bodies were sintered in a pressure sintering furnace under an argon atmosphere at 1450 °C and 2 MPa (Figure 2c). The temperature curve for the sintering processes is shown in Figure 3b.

2.3. Characterization Methods

The relative density (ρ) of the samples was measured using the Archimedes drainage method in accordance with ASTM C373 [33]. A precision electronic balance was used to determine the dry weight in air (W₁). The samples were then boiled in deionized water for 4 h to obtain the wet weight (W₂). Subsequently, the suspended weight in pure water (W₃) was measured. The densities were calculated using the following equations:

$$\mathrm{ }{\rho }_a={\displaystyle \frac{W_1}{W_2-W_3}},$$

(1)

$${\rho }_{th}={\displaystyle \frac{m\times x_1\%+m\times x_2\%+m\times x_3\%}{\frac{m\times x_1\%}{{\rho }_1}+\frac{m\times x_2\%}{{\rho }_2}+\frac{m\times x_3\%}{{\rho }_3}}},$$

(2)

$$\rho ={\displaystyle \frac{{\rho }_{\alpha }}{{\rho }_{th}}}\times 100\%,$$

(3)

where ρ_α is the measured density of the specimen, m is the total mass of the sample, x₁, x₂, and x₃ are the mass fractions of WC, Co, and TiC, respectively, ρ₁, ρ₂, and ρ₃ are the theoretical densities of WC, Co, and TiC, respectively, ρ_th is the theoretical density of the specimen, and ρ is the relative density of the fabricated material.

The linear shrinkage rate of the green parts was determined by measuring the sample dimensions before and after sintering using a vernier caliper. The shrinkage rates along the x, y, and z axes were calculated based on the dimensional changes:

$$\mathrm{ }{\eta }_{x,y,z}={\displaystyle \frac{{\beta }_1-{\beta }_2}{{\beta }_1}}\times 100\%,$$

(4)

where η_x,y,z represents the linear shrinkage in x, y, or z axes, β₁ is the initial dimensions of the green parts, and β₂ is the corresponding dimension after sintering.

Surface roughness of the carbide specimen after sintering was measured using a roughness tester (RTEC LAMBDA, San Jose, CA, USA) following ISO 25178, with Ra (arithmetic mean height), Rz (mean roughness depth), Rsk (profile skewness) and Rku (profile kurtosis) as the surface roughness indicator according to [34]:

$$Ra={\displaystyle \frac{1}{L_l}}{\int }_0^{l}f(x)dx,$$

(5)

$$R={\displaystyle \frac{1}{5}}\sum _{i=1}^5(Z_{\rho ,i}+Z_{v,i}),$$

(6)

$$Rsk={\displaystyle \frac{1}{R{q}^3}}{\displaystyle \frac{1}{L_2}}{\int }_0^{l}Z(x{)}^{3}dx,$$

(7)

$$Rku={\displaystyle \frac{1}{R{q}^4}}{\displaystyle \frac{1}{L_3}}{\int }_0^{l}Z(x{)}^{4}dx,$$

(8)

where L₁, L₂ and L₃ are the test gauge length, Rq is the root mean square roughness, Z_p,i is the peak height, and Z_v,i is the valley depth.

The phase composition of the carbide specimen was analyzed using X-ray diffraction (XRD, BRUKER D8 ADVANCE, BRUKER, Billerica, MA, USA) with a copper target, a scanning speed of 0.02°/s over a 2θ range of 20–90°, and an X-ray wavelength of λ = 1.54056 nm.

The microstructure of the samples was observed using a high-resolution field-emission scanning electron microscope (SEM, Quanta400, FEl, Amsterdam, The Netherlands).

The Vickers hardness of the samples was tested following ASTM E384 using a Vickers hardness tester (HVS-30Z, Shanghai Precision Instrument Co., Ltd., Shanghai, China) with a 136° diamond indenter under 30 kgf for 15 s [35]. The hardness was determined per the following equation:

$$HV=0.1891{\displaystyle \frac{F_1}{{(\frac{d_1+d_2}{2})}^2}},$$

(9)

where F₁ is the applied load, and d₁ and d₂ are the diagonal lengths of the residual indentations after indenter withdrawal.

Each sample was measured five times, and the average value was calculated to ensure accuracy.

The room-temperature flexural strength was measured using a universal testing machine (AGS-X-50KN, Shimadzu, Kyoto, Japan) in accordance with ASTM A370 [36]. A three-point bending configuration with a support span of 14.5 mm was used. The flexural strength R was determined as:

$$R={\displaystyle \frac{3F_{2}L}{2b{h}^2}},$$

(10)

where F₂ is the maximum applied load, L is the specimen length, b is the specimen width, and h is the specimen height.

For the three-point bending tests, three tests were conducted for each type of carbide to ensure the reliability of the flexural strength results.

The specific wear rate of the cemented carbide was evaluated using tribological tests on a high-temperature tribometer (THT, Anton Paar, Graz, Austria). A Si₃N₄ ball was used as the counterbody to assess the friction coefficient and wear resistance of the cemented carbide specimens. The friction coefficient (COF) was automatically recorded and the wear rate W was calculated with the equation below:

$$W={\displaystyle \frac{m_1-m_2}{\rho \times F_3\times L}}\times 100\%$$

(11)

where m₁ is the initial mass of the carbide specimen, m₂ is the mass of the carbide specimen after testing, ρ is the density, F₃ is the load, and L is the total sliding distance.

The cutting performance of the tools was evaluated by turning HT250 bars (Ø 30 mm) using cemented carbide tools with varying TiC contents on a CNC lathe (CNC6135A, Wuhan Huazhong Numerical Control Co., Ltd., Wuhan, China).

The edge morphology of the cemented carbide tools after cutting test was examined using a depth-of-field microscope (Zeiss stereo microscope, Oberkochen, Germany).

3. Results and Discussion

3.1. Relative Density and Dimensional Shrinkage

Cemented carbide samples (WC-12Co, WC-10TiC-12Co, and WC-20TiC-12Co) were fabricated using optimized printing parameters and a debinding-sintering process. As shown in Figure 4, all specimens exhibit relative densities exceeding 97%. A rigorous t-test of these results indicates that the relative density differences among these carbides are not statistically significant. These results confirm that the PEP processed carbides can achieve near-full density, demonstrating the feasibility of the printing-sintering process in this study.

After density evaluation, the dimensional shrinkage rates along different orientations were measured. A rectangular block with initial dimensions of 26 mm × 8.5 mm × 7 mm was designed and PEP processed with WC-xTiC-12Co carbides. The morphology of specimens after printing, degreasing, and sintering is shown in Figure 5. Relative to the model dimensions, the PEP-printed carbide components exhibit approximately 2% expansion along the x-axis, 8.5% expansion along the y-axis, and 4% contraction along the z-axis. This anisotropic dimensional change is attributed to the layer-by-layer deposition process in additive manufacturing. The extruded slurry, which retains some fluidity due to elevated temperature, preferentially flows along the X-Y plane. Simultaneously, limitations imposed by layer thickness and nozzle pressure lead to a lateral redistribution of excess material within the X-Y plane, as noted in reference [37]. This phenomenon, compounded by gravitational effects, results in dimensional changes characterized by expansion in the horizontal directions and contraction in the thickness direction.

After two-step debinding, dimensional changes of less than 0.2% have been observed. During the initial debinding phase, residual organic binders remain in the green body, with some acting as structural linkages and resulting in minimal shrinkage. In the secondary debinding phase, complete removal of the binders generates a porous structure. Although the pre-sintered green body shows moderate enhancement in mechanical strength, no significant shrinkage occurs at this stage.

Compared with debinding, sintering induces significantly greater shrinkage. The volumetric shrinkage rates of WC-12Co, WC-10TiC-12Co, and WC-20TiC-12Co are 44.1%, 50.4%, and 52.1%, respectively, relative to the STL model. As shown in Figure 6, the linear dimensional shrinkage rates increase with rising TiC content while remaining consistent across the same axes for all three carbides, highlighting the controllable anisotropic shrinkage of PEP-printed cemented carbides [38]. Due to the relatively loose interlayer stacking of the printed green body in the thickness direction, the most substantial shrinkage after sintering occurs in the z-direction. The measured z-axis shrinkage rates for WC-12Co, WC-10TiC-12Co, and WC-20TiC-12Co are 24.48%, 27.71%, and 28%, respectively.

3.2. Microstructure Analysis

Organic binders used in extrusion-based additive manufacturing are typically macromolecular, often leaving carbon residues from incomplete debinding. This residual carbon can lead to the formation of free carbon phases after sintering [10]. Single-step debinding can easily leave residual carbon from the binder according to [39], introducing notable free carbon in the sintered samples. In contrast, a two-step debinding process employed in this study ensures the complete removal of organic binders, effectively suppressing the formation of free carbon during sintering based on references [10,32].

Figure 7 shows the XRD patterns of cemented carbides with varying TiC content. For WC-12Co, the primary phases detected are WC and Co. In WC-10TiC-12Co and WC-20TiC-12Co, the dominant phases are WC, TiC, and Co, with no evidence of carbon-deficient phases, free carbon, or other impurities. Despite identical processing parameters, variations in TiC content result in noticeable differences in surface phase composition, as indicated by fluctuations in TiC peak intensities. The XRD results confirm that the experimental protocol effectively controls residual carbon from the debinding process.

The cross-sectional microstructure of WC-xTiC-12Co cemented carbides is shown in Figure 8. After sintering, WC grains predominantly exhibited truncated triangular or triangular morphologies. The WC grain size distributions, analyzed using ImageJ software (ImageJ 1.x, U.S. National Institutes of Health, Bethesda, MD, USA), are shown in Figure 9, with median grain sizes (d50) summarized in

Table 3. Average WC grain size of WC-xTiC-12Co carbides.

Sample	WC-12Co	WC-10TiC-12Co	WC-20TiC-12Co
d50 (μm)	0.98	0.88	0.87

. The WC grain sizes ranged from 0.87 to 0.98 μm, with only a small fraction exceeding 2 μm, indicating no significant abnormal grain growth. The increase of TiC content clearly reduces WC grain size to a notable degree, indicating the grain refinement effect of TiC.

Sintering is the most critical stage for microstructural evolution in cemented carbides, consisting of four stages: presintering, solid-state sintering, liquid-phase sintering, and cooling [40]. The liquid-phase sintering stage (above 1280 °C) dominates densification and porosity reduction while promoting WC grain growth via Ostwald ripening. In this stage, smaller WC grains dissolve in the liquid Co phase, and solute atoms diffuse toward larger WC grains due to their lower solubility. This dissolution-reprecipitation mechanism leads to WC grain coarsening and improved relative density [41].

As shown in Table 3, the average WC grain size decreased with increasing TiC content, demonstrating a strong correlation between TiC addition and grain refinement. TiC effectively suppresses both WC grain growth and abnormal coarsening of WC grains via restraining the dissolution-reprecipitation process of WC grains during liquid phase sintering [7,9,42].

3.3. Mechanical Properties

The Vickers hardness of cemented carbides with varying TiC content is shown in Figure 10. The hardness of WC-12Co, WC-10TiC-12Co, and WC-20TiC-12Co are 1317 HV30, 1403 HV30, and 1496 HV30, respectively. t-tests reveal that the Vickers hardness of the three cemented carbide formulations differs significantly between each pairwise comparison. The addition of TiC notably enhances the hardness due to the WC grain size refinement (Figure 9), which is consistent with the results in [9,43].

Figure 11 presents the three-point flexural strength test results. The flexural strength decreases from 2025 MPa to 915 MPa with the TiC content increasing from 0 to 20 wt.%. t-tests reveal a statistically significant difference in flexural strength between WC-12Co and WC-20TiC-12Co. This reduction is attributed to microstructural heterogeneities caused by TiC addition, which promote more significant stress concentration and the reduction of fracture toughness [9].

The tribological properties of sintered WC-12Co, WC-10TiC-12Co, and WC-20TiC-12Co were evaluated using Si₃N₄ balls as counterbodies. Figure 12a and Figure 12b show the friction coefficient and wear rate results, respectively. The average friction coefficients for WC-12Co, WC-10TiC-12Co, and WC-20TiC-12Co are 0.56, 0.51, and 0.47, while their corresponding wear rates were 91.828 × 10⁻⁶ mm³/(N·m), 77.843 × 10⁻⁶ mm³/(N·m), and 43.034 × 10⁻⁶ mm³/(N·m), respectively.

These results demonstrate that adding TiC not only reduces the friction coefficient but also significantly improves wear resistance. The wear rate decreases by 15.2% and 53.1% for 10 wt.% and 20 wt.% TiC additions, respectively, as compared with plain WC-12Co. This improvement is closely related to the increased hardness of TiC-containing carbides.

Figure 10, Figure 11 and Figure 12 illustrate the trade-off between hardness (wear resistance) and flexural strength in cemented carbides, a common trend across many grades. TiC addition enhances hardness and wear resistance, as it is harder than WC, but reduces toughness and ductility, leading to lower flexural strength in WC-TiC-Co carbides. To boost the flexural strength of TiC-containing carbides, strategies such as reducing particle size and applying post-sintering treatments like hot isostatic pressing (HIP) are recommended. Despite their lower flexural strength, WC-TiC-Co carbides offer advantages in oxidation resistance, wear resistance, and red hardness over plain WC-Co carbides, showing great potential in metal cutting, milling, and molding.

3.4. Cutting Performance

The cutting performance of PEP processed WC-xTiC-12Co carbide tools was evaluated through turning tests on HT250 bars (diameter: 30 mm) for 4 min and 8 min. The cutting parameters are listed in

Table 4. Main cutting parameters for WC-xTiC-12Co carbide cutting HT250.

Main Cutting Parameters	Cutting Speed (m/min)	Cutting Speed (mm)	Feed Rate (mm/min)
Values	47.1	1.6	50

. Figure 13 illustrates the cutting process using the fabricated tools.

The assessment of tool wear was based on the measurement of flank wear depth, with a lower value indicating superior wear resistance. Figure 14 illustrates the wear morphologies of the tools after 4 and 8 min of cutting, as observed via a depth-of-field microscope. The results indicate that carbide tools incorporating TiC exhibit significantly reduced flank wear depths in comparison to the TiC-free WC-12Co tool. Figure 15 presents a quantitative comparison of the flank wear depth, as determined by ImageJ. The WC-12Co tool demonstrates wear depths of 0.783 mm after 4 min of cutting and 1.104 mm after 8 min. In contrast, the WC-10TiC-12Co tool shows wear depths of 0.524 mm and 0.574 mm, while the WC-20TiC-12Co tool exhibits the shallowest wear depths of 0.311 mm and 0.367 mm, after 4 and 8 min of cutting, respectively. Figure 14 and Figure 15 clearly demonstrate that the cutting performance improves more significantly with higher TiC content as the cutting test duration increases. The flank wear progression typically occurs in three stages: initial wear, normal wear, and severe wear [44]. In WC-12Co, the wear depth increases significantly from 0.783 mm (4 min of cutting) to 1.104 mm (8 min of cutting), indicating a rapid transition to the severe wear stage. In contrast, WC-10TiC-12Co and WC-20TiC-12Co show minimal differences in wear depth between 4 min (0.524 mm and 0.311 mm) and 8 min (0.574 mm and 0.367 mm), suggesting a delayed onset of severe wear and prolonged normal wear stages. This effect, driven by TiC addition, enhances tool durability.

Table 5. Mechanical testing summary for WC-xTiC-12Co carbides.

Sample	Unit	WC-12Co	WC-10TiC-12Co	WC-20TiC-12Co
Relative density	%	97.9	98.8	99.4
Hardness	HV30	1317	1403	1496
Flexural strength	MPa	2025	1434	915
Friction coefficient		0.56	0.51	0.47
Tribological Test: Wear rate	mm3/(N·m)	91.828 × 10−6	77.843 × 10−6	43.034 × 10−6
Cutting Test: Wear value/4 min	mm	0.783	0.524	0.311
Cutting Test: Wear value/8 min	mm	1.104	0.574	0.367

summarizes the main properties of WC-xTiC-12Co carbide. The enhanced flank wear resistance is ascribed to the augmented hardness and elevated relative density of TiC-bearing carbides. In particular, WC-20TiC-12Co, attaining the highest hardness and a relative density of 99.4%, demonstrates the most outstanding wear resistance. This underscores the importance of densification in optimizing tribological performance [45].

The material composition of cutting tools, in addition to affecting flank wear resistance, also plays a crucial role in determining the surface quality of the workpiece. Figure 16 and Figure 17 present the 3D and 2D surface roughness profiles of machined HT250, as measured by a roughness tester.

Table 6. Surface roughness parameters of HT250 after cutting test for different cutting duration.

Parameter	Unit	WC-12Co		WC-10TiC-12Co		WC-20TiC-12Co
		4 min	8 min	4 min	8 min	4 min	8 min
Ra	µm	0.847	0.736	0.789	0.644	0.846	0.638
Rz	µm	5.323	5.040	4.402	3.838	5.612	4.187
Rsk		−0.066	0.029	0.152	−0.013	−0.058	0.083
Rku		3.993	2.804	2.878	3.082	3.056	3.714

summarizes the surface roughness parameters for cutting duration of 4 and 8 min. After 4 min of cutting, the Ra values of the HT250 workpiece machined with WC-12Co, WC-10TiC-12Co, and WC-20TiC-12Co are 0.847 µm, 0.789 µm, and 0.846 µm, respectively. After 8 min of cutting, these values decrease to 0.736 µm, 0.644 µm, and 0.638 µm, respectively. Similarly, the Rz values exhibit a comparable trend. The higher surface roughness observed at 4 min compared to 8 min is linked to the initial wear stage of the cutting tools, where rapid tool wear and variable friction coefficients are dominant. In contrast, during longer cutting durations, the surface roughness exhibits a downward trend (Table 6), as all tools transition into a steady-state friction regime with stabilized wear rates [44].

4. Conclusions

This study investigated the microstructure and mechanical behavior of WC-12Co cemented carbides with varying TiC contents, fabricated via PEP additive manufacturing. The effects of TiC content on relative density, shrinkage, microstructure, mechanical properties, and cutting performance were systematically analyzed. The key findings are as follows:

(1)

The PEP additive manufacturing process has been successfully utilized to fabricate high-density cemented carbides with high TiC contents. The PEP-processed WC-12Co, WC-10TiC-12Co, and WC-20TiC-12Co achieves relative densities of 97.9%, 98.8%, and 99.4%, respectively. The average linear shrinkage rates upon sintering are 14.9–19.7%, 13.1–17.2%, and 24.4–28.0% along the x, y, and z axes, respectively, indicating controllable dimensional changes.

(2)

The addition of TiC refines the WC grain size. The average WC grain size for WC-12Co carbides with 10 wt.% and 20 wt.% TiC are 0.88 μm and 0.87 μm, respectively, compared to 0.98 μm for TiC-free WC-12Co.

(3)

The hardness of the PEP processed carbides increases with TiC content, with the maximum Vickers hardness augmented by approximately 13.6% for WC-20TiC-12Co over WC-12Co. However, TiC addition decreases flexural strength apparently. Tribological testing reveals the friction coefficient decreases while wear resistance increases with TiC content.

(4)

The TiC addition significantly enhances wear resistance of PEP processed carbides during HT250 cutting test and reduces the workpiece surface roughness. The beneficial role of TiC in improving cutting performance is more evident for longer cutting durations.

(5)

Overall, PEP-processed TiC-containing carbides show promising properties, indicating significant industrial potential in metal cutting, milling, and molding. Future research on PEP-processed cemented carbides could focus on optimizing carbide particle size, designing organic binder materials, developing TaC/NbC-containing carbides, and exploring advanced sintering techniques like microwave sintering. Additionally, creating cutting tools with more complex geometries is another potential research direction.