Silicon Nitride FSW Tool Composition for Durable High-Temperature Welding
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Solution Overview
Problem
Friction stir welding tool members made of silicon nitride sintered bodies face challenges in oxidation resistance, leading to reduced long-term life, despite improvements in wear resistance and fracture toughness.
Innovation Solution
A friction stir welding tool member made of a silicon nitride sintered body with 15% or less of additive components, including lanthanoid elements and Mg, Ti, Hf, and Mo, which form a grain boundary phase that enhances oxidation resistance and sinterability, improving the tool's durability and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cBN, SiC, and TiN are added in a content as large as 20 vol. % to improve wear resistance, then wear resistance is improved to a certain degree, but sinterability becomes difficult and dense sintered body cannot be obtained
Solution Approach 1:
The patent changes the chemical composition parameters by replacing 20 vol.% of cBN/SiC/TiN with specific sintering aids (Y2O3, Al2O3, TiO2, SiO2, C in controlled ratios), transforming the material from difficult-to-sinter high-wear-resistance composition to optimally-sintered composition with balanced properties
Solution Approach 2:
The patent creates a composite sintering aid system combining multiple oxides (Y2O3, Al2O3, TiO2, SiO2) and carbon in specific proportions, where each component contributes to different aspects of sintering behavior, achieving both dense sintering and maintained wear resistance
2Ease of manufacture
If yttrium (Y) is used as a sintering aid to improve sinterability, then dense sintered body can be obtained, but oxidation resistance is lowered
Solution Approach 1:
The patent merges Y2O3 (providing sinterability) with Al2O3 and TiO2 (providing oxidation resistance) in a composite sintering aid system, where the combination achieves both dense sintering and improved oxidation resistance that neither component could achieve alone
Solution Approach 2:
Al2O3 and TiO2 act as intermediary components that mediate between Y2O3's sintering promotion effect and the oxidation resistance requirement, forming a protective grain boundary phase that prevents oxidation while maintaining sintering efficacy
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 tool exhibits improved oxidation resistance and long-term life, maintaining high durability and wear resistance even at high temperatures, with a friction coefficient that supports efficient welding processes.
Implementation Method 1
the additive components include at least one element selected from lanthanoid elements and at least one element selected from Mg, Ti, Hf, and Mo
Implementation Method 2
a silicon nitride sintered body contains 15% by mass or less of additive components other than silicon nitride
Data Source
AI summary
The friction stir welding tool member according to the present invention is made of a silicon nitride sintered body, wherein the silicon nitride sintered body contains 15% by mass or less of additive components except silicon nitride in such a manner that the additive components include at least one element selected from lanthanoid elements and at least one element selected from Mg, Ti, Hf, and Mo. In addition, it is preferable that the additive components further include at least one element selected from Al, Si, and C. According to the above-described configuration, a friction stir welding tool member having an excellent durability can be provided.