PVD Coated Cutting Tool Substrate Composition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing PVD-coated cutting tools face challenges with brittleness and flaking when applied to substrates with high toughness and sharp geometries, particularly those with high cobalt content, which compromises both hardness and edge line toughness.
Innovation Solution
A coated cutting tool is developed using a fine-grained cemented carbide substrate with a cobalt content of 12.5-17 wt%, a Cr/Co weight ratio of 0.05-0.15, and a Ti content of 50-300 ppm, combined with a PVD coating that has a hardness of 20-50 GPa and compressive stresses, which can be either a single homogenous layer or a multilayered structure, including nitrides, oxides, or carbides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a PVD coating is applied to a substrate with high cobalt content (12.5-17 wt%) to achieve high toughness, then the substrate toughness is improved, but the substrate hardness decreases making the coating application difficult
Solution Approach 1:
The patent changes the chemical composition parameters of the cemented carbide substrate by adding chromium (0.5-2.0 wt%) and titanium (50-300 ppm) to modify the properties of the cobalt binder phase. This allows achieving both high toughness (12.5-17 wt% Co) and sufficient hardness for PVD coating application, resolving the contradiction between toughness and coating applicability
Solution Approach 2:
The patent creates a composite cemented carbide material combining WC grains with a modified Co-Cr-Ti binder phase. The composite structure provides both the toughness from high cobalt content and the hardness from chromium and titanium additions, enabling successful PVD coating application on high-toughness substrates
2Strength
If a PVD coating is applied to a substrate with sharp geometries to achieve wear resistance, then the coating provides high hardness and wear resistance, but the coating becomes brittle and causes flaking
Solution Approach 1:
The patent modifies the substrate properties by adding chromium and titanium to the cobalt binder, creating a binder phase with optimized mechanical properties. This modified binder provides better ductility and stress distribution, reducing the brittleness issue when PVD coatings are applied to sharp geometries and preventing coating flaking
3Ease of manufacture
If a fine-grained substrate is used to increase hardness for coating compatibility, then the substrate hardness is improved, but the edge line toughness decreases
Solution Approach 1:
The patent creates a composite cemented carbide with fine WC grains (mean particle diameter 0.2-0.5 μm) combined with a specially formulated Co-Cr-Ti binder phase. The fine grain structure provides hardness and coating compatibility, while the chromium and titanium in the binder maintain edge line toughness by enhancing the binder's ductility and toughness properties
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 solution enhances the toughness and hardness of the cutting tool, leading to improved edge line toughness and extended tool life by preventing edge line breakage or chipping during milling operations in stainless steel, as demonstrated by increased tool life in face milling tests.
Implementation Method 1
The coated cutting tool comprises a substrate and a PVD coating
Data Source
AI summary
The present invention relates to a coated cutting tool comprising a PVD coating and a cemented carbide substrate comprising Co in an amount of 12.5-17 wt%, Cr in an amount such that the Cr/Co weight ratio is 0.05-0.15, a Ti of between 50 to 300 ppm by weight and a CW_Cr value between 0.8-0.97.