Cemented Carbide Surface Hardness via Grain Gradient
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Solution Overview
Problem
Cemented carbide materials face challenges in achieving a balance between toughness, hardness, and wear resistance, particularly in applications like rock drilling and metal machining, where early impact damage is a concern due to insufficient surface toughness and varying demands on material properties across different parts of a tool.
Innovation Solution
A method involving the application of a grain refiner compound and a grain growth promoter, such as chromium carbide and carbon, onto the surface of a WC-based compact to create a gradient of grain size and binder content during sintering, resulting in a cemented carbide body with enhanced surface hardness and impact resistance without compromising internal toughness and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the binder content is increased to improve toughness, then impact resistance improves, but hardness and wear resistance decrease
Solution Approach 1:
The patent applies different binder contents to different zones of the cemented carbide body. The surface zone has a lower binder content (4-10 wt%) to provide hardness and wear resistance, while the interior zone has a higher binder content (10-15 wt%) to provide toughness and impact resistance. This spatial differentiation of material properties resolves the contradiction between surface wear resistance and internal toughness.
Solution Approach 2:
The patent transitions from a homogeneous material composition to a gradient composition that varies through the depth dimension. By controlling the binder content to decrease from the interior toward the surface, the patent creates a three-dimensional distribution of properties that simultaneously satisfies conflicting requirements at different locations within the same component.
2Reliability
If the grain size is reduced to improve hardness and wear resistance, then surface hardness improves, but impact resistance decreases
Solution Approach 1:
The patent creates different grain size characteristics in different zones. The surface zone has finer grain size to maximize hardness and wear resistance, while the interior zone has coarser grain size to maintain toughness and impact resistance. This local differentiation resolves the contradiction between surface hardness and bulk impact resistance.
3Ease of manufacture
If a homogeneous composition is used to simplify manufacturing, then manufacturing ease improves, but the ability to meet varying surface and interior requirements deteriorates
Solution Approach 1:
The patent changes the composition parameters (binder content and grain size distribution) as a function of position within the material. By controlling the gradient of these parameters from interior to surface, the patent achieves property differentiation without requiring separate manufacturing steps for different zones, thus maintaining manufacturing simplicity while enabling property customization.
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 method produces a cemented carbide body with significant hardness gradients, providing improved resistance to early impact damage and increased tool life, as demonstrated by increased surface hardness and wear resistance in mining tool inserts, with up to 40% longer tool life and 20% improved wear resistance in rock drilling applications.
Implementation Method 1
a grain refiner compound comprising a grain refiner and carbon and/or nitrogen... on at least one portion of the surface of a compact... sintering the compact... resulting in a cemented carbide body with enhanced surface hardness
Data Source
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AI summary
The present invention relates to a method of producing a cemented carbide body comprising providing: (1 ) a grain refiner compound comprising a grain refiner and carbon and/or nitrogen, and, (2) a grain growth promoter, on at least one portion of the surface of a compact of a WC-based starting material comprising one or more hard- phase components and a binder, and then sintering the compact, the invention also relates to a cemented carbide body comprising a WC-based hard phase and a binder phase, wherein at least one part of an intermediate surface zone has a lower average binder content than a part further into the body, and at least one part of an upper surface zone has in average a larger average WC grain size than the intermediate surface zone. The cemented carbide body can be used as a cutting tool insert for metal machining, an insert for a mining tool, or a coldforming tool.