PCBN Composite Material for High-Temperature Friction Stir Welding
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Solution Overview
Problem
Friction stir welding tools for high melting point metals like steels are limited by the tools' inability to retain properties and form at temperatures above 1000°C, leading to short lifespan and high costs due to the use of expensive, difficult-to-shape materials that suffer from wear and fracture issues.
Innovation Solution
A composite material comprising 60-90 vol.% cubic boron nitride particles and 10-40 vol.% tungsten-rhenium alloy with an aluminum interface layer, formed under high pressure and high temperature conditions, which provides enhanced wear resistance and fracture toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If steel probes are used for friction stir welding of low melting point metals, then the tool is simple and inexpensive, but the tool cannot retain its properties and form at temperatures above 1000°C, leading to short lifespan and high costs
Solution Approach 1:
The patent applies composite materials by combining cubic boron nitride (cBN) particles with a tungsten-rhenium-aluminum alloy matrix. The cBN provides high temperature stability and wear resistance, while the W-Re-Al alloy matrix provides fracture toughness and chemical inertness. This composite structure enables the tool to maintain its properties at temperatures above 1000°C while extending tool lifespan through reduced wear and fracture.
2Temperature
If expensive refractory metal alloys are used to withstand high temperatures, then the tool can operate at temperatures above 1000°C, but the material is difficult to shape and has limited life due to wear and fracture
Solution Approach 1:
The patent utilizes high pressure high temperature (HPHT) processing parameters to transform the composite material into a sintered body. By applying extreme pressure and temperature conditions during manufacturing, the cBN particles and W-Re-Al alloy matrix are consolidated into a dense, shapeable structure that can be machined into tool forms, overcoming the difficulty of shaping refractory materials.
3Loss of substance
If polycrystalline cubic boron nitride is used for wear resistance, then the tool has enhanced wear resistance, but the fracture toughness is lower than ideally required
Solution Approach 1:
The patent creates a composite material where hard cBN particles provide wear resistance while the ductile W-Re-Al alloy matrix provides fracture toughness. The aluminum in the matrix forms an interface layer at the cBN-grain boundaries, which enhances the bonding between particles and prevents crack propagation, thereby improving overall fracture toughness while maintaining wear resistance.
4Reliability
If the tool material is chemically inert and retains form at high temperatures, then the tool is suitable for steel welding, but the tools have limited life cycle and high cost per metre welded
Solution Approach 1:
The patent optimizes the composition parameters of the W-Re-Al alloy matrix, specifically controlling the aluminum content (90-99 wt% W-Re alloy with 2-10 wt% Al) to achieve the desired balance of chemical inertness, form stability, and extended tool life. The HPHT processing parameters are also optimized to create a dense microstructure that maximizes tool lifespan, thereby reducing cost per metre welded.
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 composite material significantly reduces wear and fracture, enabling the tool to withstand multiple plunges without damage and extending its lifespan, while maintaining chemical inertness and form stability during the welding process.
Implementation Method 1
the binder phase including an interface layer on the cBN grains, said interface layer comprising borides or nitrides of Al
Implementation Method 2
which are formed together under high pressure and high temperature (HPHT) conditions
Implementation Method 3
the rotation of the tool creates frictional and viscous heating of the workpieces
Implementation Method 4
the rotation of the tool creates frictional and viscous heating of the workpieces
Data Source
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AI summary
This disclosure relates a polycrystalline cubic boron nitride, PCBN, composite material for use in friction stir welding. The PCBN composite material comprises tungsten (W), rhenium (Re) and aluminium (Al) in the binder matrix material.