Cemented Carbide Carbonitride Structure for Steel Reaction Resistance
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Solution Overview
Problem
Existing cemented carbides do not exhibit sufficient reaction resistance against steel, and the inclusion of molybdenum in composite carbonitrides deteriorates welding resistance, while existing technologies do not address this issue effectively.
Innovation Solution
A method of producing cemented carbide by incorporating TiNbMCN as a carbonitride with controlled compositions of Nb and N, dispersing it uniformly to avoid dissolution in WC crystals, and controlling the content and distribution of core and peripheral portions in the cemented carbide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Mo is added to composite carbonitride to improve mechanical properties, then hardness and strength are improved, but welding resistance deteriorates
Solution Approach 1:
The invention removes Mo from the composite carbonitride composition entirely, extracting the harmful element that causes welding resistance deterioration while maintaining mechanical strength through alternative compositions of Ti, Nb, and other carbide-forming elements
Solution Approach 2:
The invention changes the compositional parameters of the composite carbonitride by specifying atomic ratios where Mo is excluded (x ≤ 0.02), and adjusts the ratios of Ti, Nb, and other elements to compensate for Mo removal, thereby maintaining mechanical properties without welding resistance penalty
2Object-generated harmful factors
If TiNbMCN is uniformly dispersed to improve reaction resistance, then welding resistance is improved, but dissolution in WC crystals occurs
Solution Approach 1:
The invention creates local compositional differentiation within the composite carbonitride particles by defining core portions with specific compositions (higher Ti content) and peripheral portions with different compositions, where the core provides reaction resistance while the peripheral structure prevents dissolution into WC crystals
Solution Approach 2:
The invention uses a composite structure within the composite carbonitride itself, combining TiNbMCN with controlled core and peripheral regions that have different compositional characteristics, where the core provides the desired reaction resistance and the peripheral structure maintains compositional stability against WC dissolution
3Strength
If existing carbonitride compositions are used to improve hardness, then wear resistance is improved, but reaction resistance against steel is insufficient
Solution Approach 1:
The invention employs a composite carbonitride structure combining TiNbMCN with specific atomic ratios and a core-peripheral architecture, where the composite nature provides both the hardness needed for wear resistance and the compositional characteristics for improved reaction resistance against steel
Solution Approach 2:
The invention applies local quality differentiation within the carbonitride particles, where the core portion enriched with Ti and Nb provides reaction resistance, while the overall composite structure maintains the hardness and wear resistance required for cutting tool performance
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3C
AI summary
A cemented carbide includes second hard phase grains each including a carbonitride containing Ti and Nb, wherein each of the second hard phase grains includes a core portion, the core portion is composed of a composite carbonitride represented by (Ti1-X-ZNbXMZC1-YNY), the M is at least one impurity element selected from a group consisting of V, Cr, and Mo, the X is more than or equal to 0.1 and less than or equal to 0.2, the Y is more than or equal to 0.3 and less than or equal to 0.6, the Z is more than or equal to 0 and less than or equal to 0.02, and in a case where a total of 70 unit regions that are each constituted of a square having each side of 8 µm are provided by successively arranging 7 unit regions in a longitudinal direction and 10 unit regions in a lateral direction in an electron microscope image of any cross section of the cemented carbide captured at a magnification of 1500x, where the total number of core portions in the total of 70 unit regions is calculated by counting the number of core portions in each of the unit regions, and where a percentage of the number of core portions in each of the unit regions with respect to the total number of core portions is calculated, the number of unit regions in which the percentage is less than 0.43% or more than 2.43% is less than or equal to 10.