A tungsten steel metallographic analysis method coordinated with a new type of corrosion system
By using ultra-precision grinding and polishing to process tungsten carbide samples and employing HF-H2O2 etching solution, the problems of insufficient pretreatment accuracy and etching solution efficiency in tungsten carbide metallographic analysis were solved, achieving high-precision and environmentally friendly analytical results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DONGGUAN HARMONY COOPERATION PLASTIC & HARDWARE TECH CO LTD
- Filing Date
- 2026-05-15
- Publication Date
- 2026-07-21
Smart Images
Figure CN122430375A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of materials analysis technology, and in particular to a metallographic analysis method for tungsten carbide that combines ultra-precision pretreatment with a novel corrosion system. Background Technology
[0002] In the fields of tungsten carbide (a hard alloy with WC as the hard phase and Co / Ni / Fe as the binder phase) material research and development, product quality inspection, and failure analysis, metallographic analysis is the core method for revealing its microstructure (such as WC grain morphology, binder phase distribution, and grain boundary characteristics). The metallographic analysis of tungsten carbide materials involves two key steps: sample pretreatment and metallographic etching. The effectiveness of these two steps directly determines the accuracy of the observation and reliability of the sample's microstructure.
[0003] Currently, the industry faces two major technical challenges in metallographic analysis of tungsten carbide:
[0004] I. Insufficient precision of sample pretreatment: Traditional tungsten carbide sample pretreatment processes (rough grinding, ordinary polishing) can only achieve a surface roughness of more than 5nm and a parallelism of more than 1μm. The surface of the pretreated sample is prone to residual scratches and poor flatness. This will not only interfere with the observation field of crystallography microscope and scanning electron microscope, but also cover up key microscopic features such as the distribution of binder phase and grain boundary details, thus leading to deviations in metallographic analysis results.
[0005] II. Poor compatibility and efficiency of etching solutions: Traditional metallographic etching methods for tungsten carbide samples mainly rely on Murakami reagent (potassium ferricyanide-potassium hydroxide solution) or hydrofluoric acid-nitric acid. The mixture. Murakami reagent shows good color development of the WC phase (hard phase) in tungsten carbide, but has weak selective etching ability for the binder phase (such as Co phase) in tungsten carbide. The etching (usually 0.5-2 minutes) barely reveals the binder phase, and the etching uniformity is poor. It is also prone to localized over-etching or under-etching, which affects the efficiency and accuracy of metallographic analysis. Hydrofluoric acid-nitric acid Mixtures are widely used due to their high solubility; however, nitric acid is a strong oxidizing agent and produces harmful nitrogen oxide waste gas during its use, which not only poses a threat to the health of operators but also pollutes the environment.
[0006] In view of the shortcomings of the existing technology, it is necessary to provide a metallographic analysis method for tungsten carbide that takes into account high processing accuracy, efficient corrosion effect and environmental friendliness. Summary of the Invention
[0007] The purpose of this invention is to provide a tungsten carbide metallographic analysis method that combines ultra-precision pretreatment with a novel corrosion system to address the shortcomings of existing technologies. This method effectively balances high processing accuracy, efficient corrosion effect, and environmental friendliness, and can effectively improve the analytical efficiency and accuracy of tungsten carbide metallographic analysis results.
[0008] To achieve the above objectives, the present invention is implemented through the following technical solutions.
[0009] A metallographic analysis method for tungsten carbide that combines ultra-precision pretreatment with a novel corrosion system includes the following steps:
[0010] Step a, wire cutting of tungsten steel billet: Diamond wire cutting technology is used to precisely cut the tungsten steel billet, controlling the flatness error of the cut surface to ±0.01mm. The cut surface of the tungsten steel billet is the metallographic corrosion surface, thus obtaining a tungsten steel sample with a metallographic corrosion surface.
[0011] Step b, Grinding of tungsten carbide samples: The metallographic corrosion surface of the tungsten carbide samples is processed at the nanoscale using an ultra-precision grinding machine;
[0012] Step c, Grinding and polishing of tungsten carbide samples: The tungsten carbide samples with metallographic corrosion surfaces are ground and polished with ultrafine diamond suspension to obtain tungsten carbide samples with surface roughness Ra≤1nm and parallelism≤0.1μm of metallographic corrosion surfaces;
[0013] Step d: Construct a novel corrosion system: Mix a 50% hydrogen peroxide solution and a 10% hydrofluoric acid solution at a volume ratio of 1:1 to obtain an HF-H2O2 corrosion solution.
[0014] Step e, metallographic etching of tungsten carbide samples: The tungsten carbide samples that have been ground and polished in step c are slowly immersed in the HF-H2O2 etching solution prepared in step d for etching treatment;
[0015] Step f, Post-etching treatment: After the metallographic etching of the tungsten carbide sample is completed, the tungsten carbide sample is taken out of the HF-H2O2 etching solution, and then the metallographic etching surface of the tungsten carbide sample is cleaned and dried.
[0016] Step g, Metallographic observation: The metallographic corrosion surface of the tungsten carbide sample after cleaning and drying is observed by crystallography or scanning electron microscopy to obtain information on the microstructure and grain size of the tungsten carbide sample.
[0017] Specifically, in step b, the nanoscale processing of the metallographic corrosion surface of the tungsten carbide sample includes the following steps:
[0018] Step b1: Use a 400# diamond grinding head on an ultra-precision grinding machine to perform wet grinding on the metallographic corrosion surface of the tungsten carbide sample. The grinding pressure is 0.1 MPa and the grinding time is 5-8 minutes.
[0019] Step b1: Use an ultra-precision grinding machine with a 1200# diamond grinding head to perform wet grinding on the metallographic corrosion surface of the tungsten steel sample. The grinding pressure is 0.1MPa and the grinding time is 5-8 minutes.
[0020] In step c, the step of grinding and polishing the metallographic corrosion surface of the tungsten carbide sample with an ultrafine diamond suspension includes:
[0021] Step c1: Use an ultrafine diamond suspension with a diamond particle size of 0.5 μm to grind and polish the metallographic corrosion surface of the tungsten carbide sample. The polishing machine speed is 150 r / min and the polishing time is 10-15 minutes.
[0022] Step c1: Use an ultrafine diamond suspension with a diamond particle size of 0.2 μm to grind and polish the metallographic corrosion surface of the tungsten carbide sample. The polishing machine speed is 150 r / min and the polishing time is 10-15 minutes.
[0023] In step e, the liquid level of the HF-H2O2 etching solution is 2-3 mm higher than the metallographic etching surface of the tungsten steel sample, and the temperature of the HF-H2O2 etching solution is 25°C, with an etching time of 15-30 seconds.
[0024] Specifically, step f, the cleaning and drying treatment of the metallographic corrosion surface of the tungsten carbide sample, includes the following steps:
[0025] Step f1: Perform ultrasonic cleaning on the metallographic corrosion surface of the tungsten carbide sample to remove corrosion products from the metallographic corrosion surface of the tungsten carbide sample.
[0026] Step f2: Rinse the metallographic corrosion surface of the tungsten carbide sample with flowing distilled water for 30 seconds;
[0027] Step f3: Dehydrate the metallographic corrosion surface of the tungsten carbide sample with anhydrous ethanol;
[0028] Step f4: Place the tungsten carbide sample in a vacuum drying oven for vacuum drying.
[0029] In step g, the approximate corrosion of the metallographic corrosion surface of the tungsten steel sample is first observed using a crystallographic microscope, and then the grains of the tungsten steel sample are photographed and observed using a scanning electron microscope to obtain information on the microstructure and grain size of the tungsten steel sample.
[0030] Compared with the prior art, the present invention has the following beneficial effects, specifically:
[0031] 1. This invention achieves a roughness of 1nm and a parallelism of 0.1μm on the metallographic corrosion surface of tungsten carbide samples through nano-level grinding on an ultra-precision grinding machine and grinding and polishing with an ultra-fine diamond suspension. This completely eliminates surface defects caused by traditional processing, providing a clean and flat sample substrate for observation by crystallography and scanning electron microscopy. This allows for the precise presentation of microscopic features such as WC phase grain morphology, binder phase distribution, and grain boundary details, significantly improving the clarity of observation and the accuracy of analysis.
[0032] 2. This invention proposes to use HF-H2O2 etching solution as metallographic etching solution. HF-H2O2 etching solution has a stronger selective etching ability on the binder phase in tungsten steel. Compared with alkaline etching solutions (such as Murakami reagent), this invention has the advantage of better surface uniformity and can effectively avoid local over-etching or under-etching. This can effectively solve the problem that the metallographic structure of certain types of tungsten steel is difficult to be clearly displayed.
[0033] 3. Therefore, the tungsten carbide metallographic analysis method of the present invention, which combines ultra-precision pretreatment with a novel corrosion system, can effectively balance high processing accuracy, efficient corrosion effect, and environmental friendliness, and can effectively improve the analysis efficiency and accuracy of tungsten carbide metallographic analysis results. Attached Figure Description
[0034] The present invention will be further described below with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention.
[0035] Figure 1 This is a schematic diagram of the structure of a tungsten carbide sample after pretreatment.
[0036] Figure 2 This is a schematic diagram of the metallographic corrosion of a tungsten carbide sample.
[0037] Figure 3 This is a metallographic image obtained by a crystallography microscope according to the present invention.
[0038] Figure 4 This is a metallographic image obtained by scanning electron microscopy in this invention.
[0039] Figure 5 The metallographic images are obtained by crystallography of tungsten carbide samples after metallographic etching with Murakami reagent using existing techniques.
[0040] Figure 6 The image shows a metallographic image of a tungsten carbide sample obtained by scanning electron microscopy after metallographic etching with Murakami reagent using existing techniques. Detailed Implementation
[0041] The present invention will now be described in conjunction with specific embodiments.
[0042] Example 1: A metallographic analysis method for tungsten carbide using a synergistic approach of ultra-precision pretreatment and a novel corrosion system, comprising the following steps:
[0043] Step a) Wire EDM of Tungsten Carbide Billet: Tungsten carbide billets are precisely cut using diamond wire EDM technology, controlling the flatness error of the cut surface to ±0.01mm to avoid initial damage. The cut surface of the tungsten carbide billet becomes the metallographic corrosion surface, thus obtaining a tungsten carbide sample with a metallographic corrosion surface, such as... Figure 1 As shown;
[0044] Step b, Grinding of tungsten carbide samples: The metallographic corrosion surface of the tungsten carbide samples is processed at the nanoscale using an ultra-precision grinding machine;
[0045] Step c, Grinding and polishing of tungsten carbide samples: The tungsten carbide samples with metallographic corrosion surfaces are ground and polished with ultrafine diamond suspension to obtain tungsten carbide samples with surface roughness Ra≤1nm and parallelism≤0.1μm of metallographic corrosion surfaces;
[0046] Step d: Construct a novel corrosion system: Mix a 50% hydrogen peroxide solution and a 10% hydrofluoric acid solution at a volume ratio of 1:1 to obtain an HF-H2O2 corrosion solution.
[0047] Step e, metallographic corrosion of tungsten carbide samples: such as Figure 2 As shown, the tungsten steel sample after grinding and polishing in step c is slowly immersed in the HF-H2O2 etching solution prepared in step d for etching treatment; wherein, the HF-H2O2 etching solution is prepared and used immediately to ensure the activity of the etching solution and avoid failure.
[0048] Step f, Post-etching treatment: After the metallographic etching of the tungsten carbide sample is completed, the tungsten carbide sample is taken out of the HF-H2O2 etching solution, and then the metallographic etching surface of the tungsten carbide sample is cleaned and dried.
[0049] Step g, Metallographic observation: The metallographic corrosion surface of the tungsten carbide sample after cleaning and drying is observed by crystallography or scanning electron microscopy to obtain information on the microstructure and grain size of the tungsten carbide sample.
[0050] It should be noted that the tungsten carbide metallographic analysis method of the synergistic ultra-precision pretreatment and novel corrosion system in this embodiment first achieves the pretreatment process of the tungsten carbide sample through nano-level grinding on an ultra-precision grinding machine and grinding and polishing with an ultra-fine diamond suspension. After the above pretreatment process, the surface roughness Ra of the metallographic corrosion surface of the tungsten carbide sample is ≤1nm and the parallelism is ≤0.1μm. For high-quality tungsten carbide (such as M78) sintered from submicron-level powder, due to its extremely small WC grain size, the above pretreatment process can effectively lay the foundation for subsequent microscopic observation.
[0051] It should be further noted that, regarding the HF-H2O2 etching solution in Example 1, during the metallographic etching of tungsten steel samples, H2O2 acts as an oxidant and HF as a complexing agent. The synergistic effect of the two determines the etching effect. Specifically, HF can provide fluoride ions. It forms stable fluorine complexes with various metal ions, such as These fluorine complexes typically have high solubility and can promote the continuous dissolution of metals. For tungsten carbide, the chemical differences between the WC and Co phases are the basis for selective corrosion. HF-H2O2 etching solution can effectively distinguish these two phases and form obvious contrasts on different phases.
[0052] It should be emphasized that the tungsten carbide metallographic analysis method of ultra-precision pretreatment and novel corrosion system in this embodiment achieves a roughness of 1nm and a parallelism of 0.1μm on the metallographic corrosion surface of the tungsten carbide sample through nano-level grinding on an ultra-precision grinding machine and grinding and polishing with ultra-fine diamond suspension. This can completely eliminate surface defects caused by traditional processing, providing a clean and flat sample substrate for observation by crystallography and scanning electron microscopy. This allows the microscopic features such as WC phase grain morphology, binder phase distribution, and grain boundary details to be accurately presented, greatly improving the clarity of observation and the accuracy of analysis.
[0053] It should be further emphasized that the tungsten carbide metallographic analysis method synergistically employing ultra-precision pretreatment and a novel corrosion system in Example 1, through optimization of the corrosion system and the proposed use of HF-H2O2 as the metallographic etching solution, and targeted optimization of the hydrogen peroxide-hydrofluoric acid corrosion system, demonstrates a stronger selective etching ability for the binder phase in tungsten carbide. In an acidic environment, H2O2 acts as an oxidant, reacting with and dissolving the binder phase, thus creating a stark contrast with the slightly etched WC. This selectivity allows researchers to clearly observe the grain size, shape, distribution, and continuity of WC. (Combined with comparison...) Figures 3-6It can be seen that, compared with alkaline etching solutions (such as Murakami reagent), the tungsten carbide metallographic analysis method of ultra-precision pretreatment and novel etching system in this embodiment has the advantage of better surface uniformity and can effectively avoid local over-etching or under-etching. This can effectively solve the problem of the difficulty in clearly displaying the metallographic features of certain types of tungsten carbide.
[0054] Furthermore, when metallographically etching tungsten steel samples with HF-H2O2 etching solution, the reduction products of hydrogen peroxide are water and oxygen, meaning that the novel etching system in Example 1 theoretically has better environmental friendliness.
[0055] In summary, the tungsten carbide metallographic analysis method of ultra-precision pretreatment and novel corrosion system in this embodiment can effectively balance high processing accuracy, efficient corrosion effect, and environmental friendliness, and can effectively improve the analysis efficiency and accuracy of tungsten carbide metallographic analysis results.
[0056] Example 2 differs from Example 1 in that: in step b, the nanoscale processing of the metallographic corrosion surface of the tungsten steel sample includes the following steps, specifically:
[0057] Step b1: Use a 400# diamond grinding head on an ultra-precision grinding machine to perform wet grinding on the metallographic corrosion surface of the tungsten carbide sample. The grinding pressure is 0.1 MPa and the grinding time is 5-8 minutes.
[0058] Step b1: Use an ultra-precision grinding machine with a 1200# diamond grinding head to wet grind the metallographic corrosion surface of the tungsten carbide sample to eliminate the machining marks from the previous stage. In this step, the grinding pressure is 0.1 MPa and the grinding time is 5-8 minutes.
[0059] Example 3 differs from Example 1 in that: in step c, the step of grinding and polishing the metallographic corrosion surface of the tungsten carbide sample with an ultrafine diamond suspension includes:
[0060] Step c1: Use an ultrafine diamond suspension with a diamond particle size of 0.5 μm to grind and polish the metallographic corrosion surface of the tungsten carbide sample. The polishing machine speed is 150 r / min and the polishing time is 10-15 minutes.
[0061] Step c1: Use an ultrafine diamond suspension with a diamond particle size of 0.2 μm to grind and polish the metallographic corrosion surface of the tungsten carbide sample. The polishing machine speed is 150 r / min and the polishing time is 10-15 minutes.
[0062] Example 4 differs from Example 1 in that: in step e, the liquid level of the HF-H2O2 etching solution is 2-3 mm higher than the metallographic etching surface of the tungsten steel sample, and the temperature of the HF-H2O2 etching solution is 25°C, with an etching time of 15-30 seconds.
[0063] Example 5 differs from Example 1 in that: in step f, the cleaning and drying treatment of the metallographic corrosion surface of the tungsten carbide sample specifically includes the following steps:
[0064] Step f1: Perform ultrasonic cleaning on the metallographic corrosion surface of the tungsten carbide sample to remove the corrosion products on the metallographic corrosion surface of the tungsten carbide sample. It should be explained that since metallographic corrosion may form a layer of corrosion products, such as oxides and salts, on the metallographic corrosion surface of the tungsten carbide sample, this layer of corrosion products will cover the underlying microstructure, so it is necessary to remove it by ultrasonic cleaning.
[0065] Step f2: Rinse the metallographic corrosion surface of the tungsten carbide sample with flowing distilled water for 30 seconds;
[0066] Step f3: Dehydrate the metallographic corrosion surface of the tungsten carbide sample with anhydrous ethanol;
[0067] Step f4: Place the tungsten carbide sample in a vacuum drying oven for vacuum drying.
[0068] Example 6 differs from Example 1 in that: in step g, the approximate corrosion of the metallographic corrosion surface of the tungsten steel sample is first observed using a crystallographic microscope, and then the grains of the tungsten steel sample are photographed and observed using a scanning electron microscope to obtain information on the microstructure and grain size of the tungsten steel sample.
[0069] The above description is only a preferred embodiment of the present invention. For those skilled in the art, there will be changes in the specific implementation and application scope based on the ideas of the present invention. The content of this specification should not be construed as a limitation of the present invention.
Claims
1. A metallographic analysis method for tungsten carbide using a synergistic approach of ultra-precision pretreatment and a novel corrosion system, characterized in that, It includes the following steps, specifically: Step a, wire cutting of tungsten steel billet: Diamond wire cutting technology is used to precisely cut the tungsten steel billet, controlling the flatness error of the cut surface to ±0.01mm. The cut surface of the tungsten steel billet is the metallographic corrosion surface, thus obtaining a tungsten steel sample with a metallographic corrosion surface. Step b, Grinding of tungsten carbide samples: The metallographic corrosion surface of the tungsten carbide samples is processed at the nanoscale using an ultra-precision grinding machine; Step c, Grinding and polishing of tungsten carbide samples: The tungsten carbide samples with metallographic corrosion surfaces are ground and polished with ultrafine diamond suspension to obtain tungsten carbide samples with surface roughness Ra≤1nm and parallelism≤0.1μm of metallographic corrosion surfaces; Step d: Construct a novel corrosion system: Mix a 50% hydrogen peroxide solution and a 10% hydrofluoric acid solution at a volume ratio of 1:1 to obtain an HF-H2O2 corrosion solution. Step e, metallographic etching of tungsten carbide samples: The tungsten carbide samples that have been ground and polished in step c are slowly immersed in the HF-H2O2 etching solution prepared in step d for etching treatment; Step f, Post-etching treatment: After the metallographic etching of the tungsten carbide sample is completed, the tungsten carbide sample is taken out of the HF-H2O2 etching solution, and then the metallographic etching surface of the tungsten carbide sample is cleaned and dried. Step g, Metallographic observation: The metallographic corrosion surface of the tungsten carbide sample after cleaning and drying is observed by crystallography or scanning electron microscopy to obtain information on the microstructure and grain size of the tungsten carbide sample.
2. The metallographic analysis method for tungsten carbide based on the synergy of ultra-precision pretreatment and a novel corrosion system as described in claim 1, characterized in that, In step b, the nanoscale machining of the metallographic corrosion surface of the tungsten carbide sample includes the following steps: Step b1: Use a 400# diamond grinding head on an ultra-precision grinding machine to perform wet grinding on the metallographic corrosion surface of the tungsten carbide sample. The grinding pressure is 0.1 MPa and the grinding time is 5-8 minutes. Step b1: Use an ultra-precision grinding machine with a 1200# diamond grinding head to perform wet grinding on the metallographic corrosion surface of the tungsten steel sample. The grinding pressure is 0.1MPa and the grinding time is 5-8 minutes.
3. The metallographic analysis method for tungsten carbide based on the synergy of ultra-precision pretreatment and a novel corrosion system as described in claim 1, characterized in that, In step c, the step of grinding and polishing the metallographic corrosion surface of the tungsten carbide sample with an ultrafine diamond suspension includes: Step c1: Use an ultrafine diamond suspension with a diamond particle size of 0.5 μm to grind and polish the metallographic corrosion surface of the tungsten carbide sample. The polishing machine speed is 150 r / min and the polishing time is 10-15 minutes. Step c1: Use an ultrafine diamond suspension with a diamond particle size of 0.2 μm to grind and polish the metallographic corrosion surface of the tungsten carbide sample. The polishing machine speed is 150 r / min and the polishing time is 10-15 minutes.
4. The metallographic analysis method for tungsten carbide based on the synergy of ultra-precision pretreatment and a novel corrosion system as described in claim 1, characterized in that, In step e, the liquid level of the HF-H2O2 etching solution is 2-3 mm higher than the metallographic etching surface of the tungsten steel sample, and the temperature of the HF-H2O2 etching solution is 25°C, with an etching time of 15-30 seconds.
5. The metallographic analysis method for tungsten carbide based on the synergy of ultra-precision pretreatment and a novel corrosion system as described in claim 1, characterized in that, In step f, the cleaning and drying treatment of the metallographic corrosion surface of the tungsten carbide sample specifically includes the following steps: Step f1: Perform ultrasonic cleaning on the metallographic corrosion surface of the tungsten carbide sample to remove corrosion products from the metallographic corrosion surface of the tungsten carbide sample. Step f2: Rinse the metallographic corrosion surface of the tungsten carbide sample with flowing distilled water for 30 seconds; Step f3: Dehydrate the metallographic corrosion surface of the tungsten carbide sample with anhydrous ethanol; Step f4: Place the tungsten carbide sample in a vacuum drying oven for vacuum drying.
6. The metallographic analysis method for tungsten carbide based on the synergy of ultra-precision pretreatment and a novel corrosion system according to claim 1, characterized in that, In step g, the approximate corrosion of the metallographic corrosion surface of the tungsten steel sample is first observed using a crystallographic microscope, and then the grains of the tungsten steel sample are photographed and observed using a scanning electron microscope to obtain information on the microstructure and grain size of the tungsten steel sample.