Chromium-Alloyed Carbide Insert for Stable Dual-Zone Hardness

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Solution Overview

Problem

Existing double pressing methods for cemented carbide inserts fail to maintain distinct mechanical properties in different zones due to binder phase migration during sintering, hindering the creation of a harder and tougher zone combination.

Innovation Solution

Incorporating chromium in both zones of the cemented carbide insert, with specific binder phase and tungsten carbide grain size differences, prevents cobalt migration and maintains original powder properties, enabling a harder zone and a tougher zone through controlled sintering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If double pressing methods are used with powders having different compositions in different parts of the green body, then different mechanical properties are intended to be achieved in different parts of the sintered body, but the binder phase migrates from the larger grain size zone to the smaller grain size zone during sintering, countering the desired differences in hardness and toughness

Engineering Contradiction:

Improvehardness and toughness differentiationVSAvoidbinder phase distribution

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

Chromium is introduced as an intermediary element in the binder phase to prevent cobalt migration between zones. The chromium forms a stable alloy with cobalt that has reduced mobility during sintering, thereby maintaining the intended binder phase distribution and enabling successful differentiation of mechanical properties in different zones

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The chemical composition parameter of the binder phase is modified by adding chromium (2-15 wt% Cr measured as a fraction of total binder content). This parameter change fundamentally alters the migration behavior of the binder phase during sintering, preventing the unwanted movement from larger to smaller grain size zones

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If chromium is added to prevent binder phase migration, then the original properties of the powder grade are maintained, but if too much Cr is added, the mechanical properties of the material deteriorate

Engineering Contradiction:

Improvebinder phase distribution stabilityVSAvoidmechanical properties

Core Design Contradiction:

Stability of the object's compositionVSStrength

Solution Approach 1:

The chromium content in the binder phase is precisely controlled within the range of 2-15 wt% Cr (measured as a fraction of total binder content). This parameter optimization ensures sufficient chromium to prevent cobalt migration while avoiding excessive chromium that would deteriorate mechanical properties. The lower bound (2 wt%) is sufficient to inhibit migration, while the upper bound (15 wt%) prevents mechanical property deterioration

Inventive Principle:

Principle #35Parameter changes

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 ensures that the desired mechanical properties are preserved post-sintering, enhancing wear resistance and toughness by maintaining the original properties of the powders in different regions, thereby increasing the working lifetime of the insert.

Implementation Method 1

the binder phase will, all other things equal, migrate from the larger grain size zone to the smaller grain size zone during sintering

Methodology Applied

Scientific EffectBinder phase migration: Diffusion

Implementation Method 2

the presence of the chromium improves the plastic deformation of the cemented carbide, this enables higher compressive stresses to be introduced into the carbide when it is treated with a surface tumbling treatment

Methodology Applied

Scientific EffectPlastic deformation: Plasticity

Implementation Method 3

when it is treated with a surface tumbling treatment, such as tumbling. This increase in compressive stress provides an apparent hardness increase which improves the wear resistance

Methodology Applied

Scientific EffectSurface tumbling treatment: Shot Peening

Data Source

PatentUS20250303474A1Double pressed chromium alloyed cemented carbide insert

Publication Date: 2025.10.02 SANDVIK MINING & CONSTR TOOLS AB

AI summary

A sintered cemented carbide insert for mining or cutting applications includes a first zone having 3-18 wt % binder phase, unavoidable impurities, a balance of tungsten carbide having a mean grain size of between 0.5-20 μm. The insert includes a second zone having a same amount, within +/−3 wt %, of binder phase as the first zone, any unavoidable impurities, and a balance of tungsten carbide having an average grain size of between 0.5-20 μm. The first zone and the second zone are adjacent to each other. The average WC grain size in the first zone is different to the average WC grain size in the second zone, and the binder phase in both the first zone and the second zone has between 2-15 wt % Cr measured as a fraction of the total binder content.