Cemented Tungsten Carbide Boron Gradient for Erosion Resistance
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Solution Overview
Problem
Cemented tungsten carbide components lack the required toughness for certain applications and have shallow surface treatments that do not provide sufficient erosion resistance.
Innovation Solution
A high-cobalt-content tungsten carbide grade is used, treated with a boron nitride spray before sintering, allowing boron to diffuse into the surface regions, creating a gradient of metallic cobalt and boron that enhances hardness and erosion resistance while maintaining high toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If cemented tungsten carbide components are made with high tungsten carbide content for erosion resistance, then erosion resistance is improved, but toughness deteriorates
Solution Approach 1:
The patent applies boron nitride spray treatment specifically to surface regions where erosion potential is high, creating a localized boron-enriched zone with enhanced hardness and erosion resistance. The interior bulk material maintains its original high-toughness composition, achieving local optimization of properties rather than uniform modification throughout the component.
2Strength
If traditional boronizing treatment is applied to sintered products, then surface hardness is improved, but treatment depth is limited to shallow regions
Solution Approach 1:
The boron nitride spray treatment is applied to the green compact before sintering, allowing boron to be incorporated into the material structure during the sintering process itself. This preliminary application enables deeper boron diffusion throughout the material compared to post-sintering surface treatments, creating a more extensive treated zone.
Solution Approach 2:
The treatment utilizes the liquid phase present during sintering to enable boron diffusion. The boron nitride decomposes and boron diffuses through the liquid-phase binder, allowing deeper penetration than solid-state diffusion would permit. The gradient extends at least 10 millimeters from the surface, creating a deep treated zone with enhanced hardness and erosion resistance while maintaining high toughness in the interior.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The treatment induces residual compressive stresses, resulting in deeper erosion resistance and improved toughness, surpassing traditional boronizing methods by applying the boron nitride in a liquid phase to a green state product.
Implementation Method 1
boron from the boron nitride coating diffuses into the compact and creates a gradient of metallic cobalt/binder and boron extending inward from the surface
Implementation Method 2
the coated compact is sintered at a temperature sufficient to melt the cobalt powder
Data Source
AI summary
A cemented tungsten carbide body is formed by mixing a tungsten carbide powder and a cobalt powder together to form a powder mixture. The tungsten carbide powder makes up greater than or equal to 80 weight percent of the powder mixture, while the cobalt binder powder makes up about 1.5 weight percent to about 20 weight percent of the powder mixture. Next, the powder mixture is compacted to form a green compact, and a boron nitride coating is applied to a surface of the green compact to form a coated compact. The coated compact is sintered at a temperature sufficient to melt the cobalt powder, such that boron from the boron nitride coating diffuses into the compact and creates a gradient of metallic cobalt and boron extending inward from the surface. The metallic cobalt content increases from the surface inward, while the boron content decreases from the surface inward.