Key Takeaways & Executive Findings
- •• Synergistic regulation of temperature (950 °C), CH4 partial pressure (1.25%), and time (60 min) yields ultrafine WC-Co powder without η phase. • The oxygen loss rate of WO2 is positively correlated with temperature and methane partial pressure, while CH4 partial pressure has no significant effect on WC formation rate. • The obtained composite powder has a particle size of 128 nm, total carbon content of 6.16%, free carbon content of 0.4%, and residual oxygen content of 0.05%. • A growth rate equation for tungsten carbide was established: d(t) = 1.21 × 10^-13 exp(-12809.72/T) √t, providing a predictive tool for process optimization.
Abstract
In this study, the effects of reaction parameters on the deep-reduction and carbonization process of WO2-Co to WC-Co were studied. The results indicate that the oxygen loss rate of WO2 is positively correlated with temperature and methane partial pressure. The partial pressure of methane has no significant effect on the formation rate of WC. The carbon content and particle size of the product increase with the increase of CH4 partial pressure. By synergistically regulating the reaction temperature to 950 °C, the CH4 partial pressure to 1.25%, and the reaction time to 60 min, ultrafine WC-Co powder without h phase can be obtained. The particle size of the composite powder is 128 nm, with total carbon content of 6.16%, free carbon content of 0.4%, and residual oxygen content of 0.05%, respectively. The growth rate relationship of tungsten carbide is as follows: d(t) = 1.21 × 10^-13 exp(-12809.72/T) √t.
1. Introduction
As an important thermal spraying material, ultrafine WC-Co coating powder is widely used in the defense industry, metallurgical, petrochemical, aerospace, machinery, and other fields [1,2]. When the WC grain size in the WC-Co cemented carbide coating belongs to ultrafine or nanograins, the coating exhibits excellent mechanical properties with high hardness and wear resistance [3]. It is beneficial for obtaining coatings with ultrafine WC grains by using ultrafine or nano-WC-Co composite powder as spraying material. Therefore, ultrafine WC-Co spray powder has received widespread attention in this field [4].
Traditional industrial techniques are difficult to obtain ultrafine or nano-WC-Co powder. Firstly, the water vapor generated during the hydrogen reduction can react with tungsten oxide to form volatile WO2(OH)2, it can cause W particles to grow through the volatilization deposition mechanism [5]. Secondly, the carbonization stage of traditional technology is the process of solid-phase transfer diffusion reaction between the added carbon and tungsten, which is the speed-limiting step of the entire preparation process. Therefore, the carbonization process is strengthened by elevating the temperature. However, large particles of tungsten have a lower specific surface area, thereby reducing the nucleation sites of tungsten carbide. In addition, high temperatures lead to a significantly higher growth rate than the nucleation rate. Consequently, it is difficult to obtain nanoscale WC particles. It is reported that the preparation process of tungsten carbide follows the unreacted-core shrinking mode [6], that is, carbon gradually diffuses into the tungsten particles to form tungsten carbide. Essentially, enhancing the mass transfer and nucleation rate of the reduction carbonization process is the key to obtaining nano/ultrafine WC-Co powders.
Loading authentic research manuscript (Pages 1–5)...
Huijun Shang, Hengli Li, Weijun Li, Feng Pan, Zhan Du (2024). Preparation of ultrafine WC-Co powder via fluidized bed. Chinese Journal of Chemical Engineering. https://doi.org/10.1016/j_cjche_144878240
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoTechIntel claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the optimal reaction temperature for preparing ultrafine WC-Co powder?
The optimal reaction temperature is 950 °C, as reported in the study.
How does methane partial pressure affect the WC-Co powder properties?
Methane partial pressure does not significantly affect the formation rate of WC, but it increases the carbon content and particle size of the product.
What are the characteristics of the ultrafine WC-Co powder obtained?
The powder has a particle size of 128 nm, total carbon content of 6.16%, free carbon content of 0.4%, and residual oxygen content of 0.05%.
What is the growth rate equation for tungsten carbide?
The growth rate equation is d(t) = 1.21 × 10^-13 exp(-12809.72/T) √t, where T is temperature in Kelvin and t is time in minutes.
Why is ultrafine WC-Co powder important?
Ultrafine WC-Co powder is important because it provides coatings with excellent mechanical properties, including high hardness and wear resistance, which are beneficial in various industrial applications.
Related Technical Papers & Translations
Design and optimization of a high-efficiency distillation process for cellulosic fuel ethanol integrated with thermal coupling and molecular sieve adsorption
To address the challenges of high energy consumption and prominent costs in the traditional three-columns distillation process for cellulosic fuel ethanol, a distillation—molecular sieve coupling separation process is proposed. This process integrates a three-column (crude distillation column, first distillation column, second distillation column) system with a 3A molecular sieve adsorption deep dehydration unit. A thermal coupling network is constructed via differential pressure design (steam from medium/high-pressure columns as mutual heat sources, reboiler liquid waste heat for feed preheating), and molecular sieve adsorption conditions are optimized. The study first performs a thermodynamic consistency test on the ethanol—water system, determines optimal non-random two-liquid (NRTL) model binary interaction parameters via experimental data regression for Aspen Plus simulation. Aiming at minimum total annual cost (TAC), Aspen Plus is used to optimize process parameters (theoretical tray number, feed location, reflux ratio, side-draw position, etc.). Economic analysis shows this process reduces CO2 emission costs by 27.56%, TAC by 15.58% (to 5.123 × 106 USD·a-1), and increases ethanol purity to ＞99.6%, providing an effective solution for green, efficient separation.
A cohesion loss model for determining residual strength of deep bedded sandstone
Rock residual strength, as an important input parameter, plays an indispensable role in proposing the reasonable and scientific scheme about stope design, underground tunnel excavation and stability evaluation of deep chambers. Therefore, previous residual strength models of rocks established were reviewed. And corresponding related problems were stated. Subsequently, starting from the effects of bedding and whole life-cycle evolution process, series of triaxial mechanical tests of deep bedded s
Federated model with contrastive learning and adaptive control variates for human activity recognition
Recent attention to privacy issues demands a communication-safe method for training human activity recognition (HAR) models on client activity data. Federated learning (FL) has become a compelling technique to facilitate model training between the server and clients while preserving data privacy. However, classical FL methods often assume independent and identically distributed (IID) data among clients. This assumption does not hold true in practical scenarios. Human activity in real-world scena