Cemented carbide has excellent properties such as wear resistance, good toughness and strength, making it the preferred material for titanium alloy machining tools.

Titanium alloy, with characteristics like light weight, high strength, wear resistance and corrosion resistance, has become a popular material in the field of consumer electronics in the 3C industry. However, titanium alloy is a typical difficult-to-machine material. Its low elastic modulus, large elastic deformation, low thermal conductivity and good affinity cause cemented carbide tools to face problems such as tool wear, tool adhesion and short machining life during titanium alloy processing. This puts forward higher requirements for the microstructural uniformity and comprehensive mechanical properties of cemented carbide tool materials.

 

(a)(d)powderA；(b)(e)powderB；(c)(f)powderC

Fig.1??SEM?of different WC powder samples

Research Background and Progress

In recent years, researchers have carried out extensive studies on inhibitor design, microstructural uniformity regulation, and mechanical property optimization of cemented carbides.

1. Beijing University of Technology has focused on exploring the influence mechanism of inhibitor composition design and its distribution characteristics on the microstructure and mechanical properties of cemented carbides. Through the collaborative regulation of grain growth inhibitor optimization and sintering densification temperature, the controllable preparation problem of improving the distribution ratio of WC/Co coherent phase boundaries and WC/WC low-energy grain boundaries in cemented alloys has been overcome.
2. Other scholars have studied the influence mechanism of Cr3C2/CrN composite additives on the phase composition, WC grain size and distribution, WC three-dimensional morphology, and mechanical properties (such as hardness, fracture toughness, and bending strength) of cemented carbides. It was found that inhibitors can slow down the WC dissolution-precipitation process, suppress WC grain aggregation and abnormal growth, and play the roles of solid solution strengthening and dispersion strengthening, effectively improving the comprehensive properties of the alloy.
3. Furthermore, scholars have prepared cemented carbides using WC powders with different particle size distributions and proposed that WC powders with poor uniformity are more prone to dissolution-precipitation and abnormal growth. Cemented carbides with uniform microstructures exhibit higher bending strength.
4. In terms of cemented carbide tools for cutting titanium alloys, some scholars have studied the influence of the physical and mechanical properties of cemented carbide tools on their milling performance of titanium alloys. The results show that tools made of alloys with better strength and toughness have the best durability and are more suitable as the base material for titanium alloy milling cutters.
5. Researchers have explored the influence of Co phase distribution uniformity on the service performance of PCB milling cutters and found that poor Co phase uniformity leads to uneven hardness in local areas of the milling cutter edge, causing uneven wear and chipping during use, which reduces the tool service life.
6. It has been pointed out that during high-speed milling of cemented carbides, the tool edge failure is dominated by adhesive wear and thermo-mechanical fatigue wear. In particular, the thermo-mechanical fatigue cracks at the edge extending to the rake face and flank face aggravate the chipping failure of the tool.

Fig.2??XRD patterns of different WC powders

Research Focus

The preparation of cemented carbide tools involves multiple steps, including powder selection, sintering of cemented carbide bars, and tool machining. Current research efforts mainly focus on the influence of the microstructure and properties of cemented carbide bars on the comprehensive performance of tools, but lack systematic studies on the correlation mechanism among powder characteristics, alloy properties, and tool cutting life. Additionally, in actual production, tools prepared from raw materials with similar powder particle sizes exhibit different machining performances.

Therefore, exploring the correlation mechanism among powder characteristics, alloy properties, and tool cutting life is of great significance, as it can provide theoretical foundations and technical support for the preparation and application of cemented carbide tools. The author selected three tungsten carbide powder raw materials with similar particle sizes, analyzed the powder characteristics, the microstructure and mechanical properties of the prepared alloys, and evaluated their cutting life, so as to reveal the correlation mechanism among powder characteristics, alloy properties, and tool cutting life.

 

(a)(d)(g)carbide A；(b)(e)(f)carbide B；(c)(f)(i)carbide C

Fig.3??SEM microstructure images and grain size distribution of cemented carbides

Experimental Methods

In the actual production of tools, there are certain differences in machining performance among tools prepared from raw materials with similar powder particle sizes. In this paper, three WC-12Co cemented carbide bars were prepared using three tungsten carbide powder raw materials with similar particle sizes, and three types of tools for titanium alloy milling were manufactured from these bars. The powder characteristics of the three raw materials, the microstructure and mechanical properties of the prepared alloys were analyzed, and cutting tests were conducted on the three types of tools to explore the correlation mechanism among the powder characteristics, alloy properties, and tool cutting life of cemented carbides.

(a)carbideA；(b)carbideB；(c)carbideC

Fig.4 ?SEM images of fracture toughness crack propagation morphology of different cemented carbide samples

(a)(d)carbide A；(b)(e)carbide B；(c)(f)carbide C

Fig.5??SEM images of fracture morphology of different cemented carbide samples

Preliminary Experimental Results

（1) Powder Particle Size Distribution Characteristics Three WC raw material powders with similar average particle sizes showed differences in particle size distribution. Their span values were 1.469, 1.274, and 1.259, respectively. Among them, Powder C had the smallest span, indicating the narrowest particle size distribution and the best uniformity, while Powder A had the worst uniformity. Hard agglomerates were observed in both Powder A and Powder B.

(2) Microstructure and Mechanical Properties of Alloys ? When using three different tungsten carbide powders to prepare cemented carbides, the alloy prepared from Powder C (with the smallest average particle size, narrowest particle size distribution, and best uniformity) exhibited the smallest average grain size and the best microstructural uniformity. ? The fracture toughness of the alloy was related to the uniformity of its grain size: the more consistent the grain size and the better the uniformity, the more complete the tungsten carbide grains, and the better the fracture toughness. Alloy C showed the best comprehensive mechanical properties, with a hardness of 1637 HV, a bending strength of 4760 MPa, and a fracture toughness of 12.3 MPa·m1/2.

(3) Influence of Powder Heredity on Tool Life ? Due to the genetic effect of powders, the presence of hard agglomerates or coarse particles in raw materials can lead to coarse sintered structures and poor WC grain uniformity in cemented carbides, causing defects such as coarse inclusions or abnormally grown particles. ? During tool cutting, these defects easily induce the nucleation and propagation of micro-cracks, leading to penetrating micro-cracks on the wear surface and shortening the tool machining life.

(a)～(c)tool A；(d)～(f)tool B；(g)～(i)tool C

Fig.7??The microstructure of the flank face of cemented carbide tools after finishing machining

Вывод

1.The mechanical properties of cemented carbide are related to the characteristics of raw material powders. Cemented carbides prepared from powders with smaller grain size, narrower particle size distribution, and better uniformity exhibit the finest grains, best microstructural uniformity, and optimal mechanical properties.

2.Hard agglomerates in raw material powders have a genetic effect, leading to defects such as coarse inclusions and abnormal grain growth in the alloy structure, which significantly deteriorate the strength and toughness of the alloy material.

3.The cutting life of cemented carbide tools is related to the mechanical properties of cemented carbides. Tools prepared from cemented carbides with the best mechanical properties have the longest cutting life.