Core-Shell Cemented Carbide for Breakage and Steel Reaction Resistance
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Solution Overview
Problem
Current hard materials, such as cemented carbides, lack excellent breakage resistance and reaction resistance against steel, with existing compositions either compromising on welding resistance or not addressing reaction resistance effectively.
Innovation Solution
A cemented carbide composition featuring first, second, and third hard phase grains, with the second hard phase grains having a core and peripheral portion of specific carbonitride compositions, and a metal binder phase, optimized for uniform dispersion and grain sizes to enhance mechanical and reaction properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional cemented carbide compositions are used, then wear resistance is maintained, but breakage resistance and reaction resistance against steel are insufficient
Solution Approach 1:
The patent employs a composite hard phase structure consisting of three distinct phases: WC grains (first hard phase), core-shell structured carbonitride grains with TiNbMCN core and TiW carbonitride shell (second hard phase), and discrete TiNbMCN carbonitride grains (third hard phase). This multi-phase composite structure synergistically combines the high strength of WC with the excellent reaction resistance of Ti-based carbonitrides, achieving both improved breakage resistance and reaction resistance against steel.
Solution Approach 2:
The second hard phase grains exhibit a core-shell structure where the core portion (TiNbMCN) provides reaction resistance and the peripheral portion (TiW carbonitride) provides structural stability. This local differentiation of material properties within the same grain structure allows simultaneous optimization of both reaction resistance (from the Ti-rich core) and mechanical strength (from the W-rich shell).
2Reliability
If Ti-based carbonitride content is increased to improve reaction resistance, then welding performance improves, but uniform dispersion and interface strength may be compromised
Solution Approach 1:
The Ti-based carbonitride phase is segmented into two distinct morphologies: core portions within shell-structured grains (second hard phase) and discrete standalone grains (third hard phase). This segmentation prevents excessive aggregation of Ti-based phases while ensuring uniform dispersion throughout the WC matrix. The core-shell structure further segments the TiNbMCN phase, isolating it within individual grains and preventing inter-granular aggregation that would compromise uniformity.
Solution Approach 2:
The patent carefully controls the compositional parameters of the carbonitride phases, specifically maintaining Nb content at 0.05-0.50 atomic ratio and controlling the Ti/W ratio in the peripheral portion. These parameter optimizations ensure that the Ti-based carbonitride phases achieve adequate reaction resistance without excessive reactivity that would cause non-uniform dispersion or interface degradation.
Data Source
AI summary
A cemented carbide includes first hard phase grains, second hard phase grains, third hard phase grains, and a metal binder phase, wherein the cemented carbide has a total of 70 unit regions, the number of unit regions each having a percentage of less than 0.43% or more than 2.43% is ≤10 among the total of 70 unit regions, the percentage being a percentage of the total number of the second and the third hard phase grains in each unit region with respect to the total number of the second and the third hard phase grains in the total of 70 unit regions, and in a total of 10 unit regions existing in a fourth row in a longitudinal direction, a percentage of the number of the third hard phase grains with respect to the total number of the second and the third hard phase grains is 5% to 15%.