Fracture Toughness Testing Equipment for Tungsten Carbide (Cemented Carbide) — Vickers Hardness Tester

Fracture Toughness Testing Equipment for Tungsten Carbide (Cemented Carbide) — Vickers Hardness Tester

Tungsten steel (cemented carbide) is manufactured through powder metallurgy sintering, utilizing tungsten carbide (WC) as the hard phase and cobalt (Co) as the binder phase. Combining high hardness with exceptional wear resistance, it serves as a core material in fields such as cutting tools, precision molds, and mining equipment.

However, tungsten steel is inherently “hard yet brittle”—the higher its hardness, the weaker its resistance to crack propagation. Fracture toughness (K_IC) is the critical metric for evaluating this resistance. It determines whether the material will undergo sudden cracking or catastrophic failure when subjected to impact loads or alternating stresses.

For critical components operating under demanding conditions, such as cutting tools and molds, hardness data alone is far from sufficient. Fracture toughness provides the other half of the answer to determining whether a tungsten steel grade is truly viable for a specific application and how long it will last.

So, which hardness tester should be used to measure fracture toughness?

Traditional fracture toughness testing methods (such as the three-point bending test and the pre-cracked beam method) require the preparation of standard specimens. This process is complex, time-consuming, and costly, making it particularly challenging for hard and brittle materials like cemented carbides.

The Vickers indentation method offers a highly efficient and practical alternative approach:

The core advantages of this method are as follows:

① Dual Functionality for Highly Efficient Testing
While a Vickers hardness tester is primarily designed to measure hardness, a single indentation can simultaneously yield fracture toughness data. This eliminates the need for additional equipment or separate specimen preparation, providing two critical metrics—hardness and toughness—from a single test.

② Minimal Specimen Requirements
There is no need to pre-crack the specimens; only flat samples with a polished surface are required, which drastically reduces specimen preparation costs. This makes the method particularly suitable for batch quality control testing of finished cemented carbide products.

③ Proven Methodology and Standardized Support
A standardized framework for this method is already well-established. Domestically, it is governed by the Chinese standard JB/T 12616-2016 (Test Method for Fracture Toughness of Cemented Carbide Tool Substrate Materials). Internationally, there are also established best-practice guidelines specifically for indentation toughness testing of cemented carbides. This ensures that measurement results are standardized and comparable.

④ Broad Application Scope
The Vickers indentation method is highly versatile, applicable to cemented carbides, cermets, and various other brittle materials. By adjusting the test load, it can be adapted to evaluate tungsten carbide grades across different hardness ranges.

Testing Procedure:
1. Fine grinding and polishing of the specimen surface to remove residual stress.

2. Use a Vickers hardness tester to create an indentation under a specified load (adjust the test force according to the specific product) to initiate the testing process.

3. Measure the indentation diagonals (for hardness calculation) and the lengths of the four corner cracks under the measuring objective lens, then apply the formula or use the measurement system to obtain the results.

The Laihua Vickers Hardness Tester series features highly precise load control and high-definition imaging. Supported by comprehensive professional technical assistance, we can help clients successfully implement and execute fracture toughness testing methods for tungsten steel.

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