Molybdenum Alloy Rotary Anode Target Hardness
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Solution Overview
Problem
Conventional molybdenum alloy rotary anode targets used in X-ray tubes and melting crucibles face issues with cracking and breaking due to low hardness when increased in size, leading to poor mechanical strength and gas emission at high temperatures.
Innovation Solution
A molybdenum alloy with controlled oxygen content and carbide distribution, specifically 0.2-1.5% by weight of titanium, hafnium, or zirconium carbides with an aspect ratio of at least 2, and a second molybdenum alloy with titanium and zirconium composite oxide, forming a laminate structure for enhanced hardness and reduced gas release, is used. Additionally, a metal or alloy layer on the electron beam irradiation face and an oxide film on other surfaces are applied for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the size of the rotary anode target is increased to a diameter of not less than 100 mm to increase output and definition, then the X-ray inspection apparatus can achieve higher output and enhanced definition, but the target becomes more prone to breaking, cracking, or other mechanical failures due to low hardness of conventional molybdenum alloy
Solution Approach 1:
The patent changes the chemical composition parameters of the molybdenum alloy by adding specific amounts of titanium (0.1-1.5 wt%), zirconium (0.01-0.5 wt%), and carbide-forming elements (0.2-1.5 wt% TiC, ZrC, HfC, or TaC), while controlling oxygen content to not more than 50 ppm. These parameter changes transform the material properties to achieve both increased hardness for mechanical strength and maintained ductility for reliability in large-size applications.
Solution Approach 2:
The patent creates a composite molybdenum alloy material by combining molybdenum base metal with carbide particles (TiC, ZrC, HfC, or TaC) and oxide inclusions (TiO2, ZrO2). This composite structure provides dispersion strengthening through the carbide particles, significantly increasing hardness and mechanical strength while maintaining the ductility needed for large-size rotary anode targets with diameter of not less than 100 mm.
2Temperature
If conventional molybdenum alloy is used in high-temperature service environment (800°C or above, 1200°C or above), then the alloy can maintain structural integrity, but gas components are evolved from the alloy resulting in deteriorated vacuum properties and contamination
Solution Approach 1:
The patent changes the chemical composition parameters by adding carbide-forming elements (0.2-1.5 wt% TiC, ZrC, HfC, or TaC) and controlling oxygen content to not more than 50 ppm. These parameter changes modify the high-temperature behavior of the alloy, reducing gas evolution through carbide formation that stabilizes the microstructure and prevents oxygen release at elevated temperatures of 800°C or above.
Solution Approach 2:
The patent converts the potential harmful effect of oxygen and carbon impurities into beneficial carbide particles (TiC, ZrC, HfC, TaC) by adding controlled amounts of carbide-forming elements. These carbide particles, which would otherwise be considered impurities, now serve as strengthening agents that prevent gas evolution at high temperatures, thus converting harmful impurities into beneficial microstructural features.
3Object-generated harmful factors
If titanium or zirconium carbide is added to improve high-temperature strength and reduce gas release, then gas release properties improve, but the alloy hardness decreases making the target prone to breaking and cracking
Solution Approach 1:
The patent optimizes the concentration parameters of carbide-forming elements (0.2-1.5 wt% TiC, ZrC, HfC, or TaC) and controls oxygen content to not more than 50 ppm. This precise parameter control ensures sufficient carbide particles for gas release suppression while maintaining adequate hardness and mechanical strength, resolving the contradiction between gas release properties and mechanical strength.
Solution Approach 2:
The patent creates local quality differences by distributing carbide particles (TiC, ZrC, HfC, TaC) and oxide inclusions (TiO2, ZrO2) throughout the molybdenum matrix. The carbide particles provide localized strengthening at critical stress points while the overall alloy maintains ductility, achieving both improved gas release properties and maintained mechanical strength.
Data Source
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AI summary
This invention provides a molybdenum alloy having excellent high-temperature strength, an X-ray tube rotary anode target having high-temperature strength, an X-ay tube, and a melting crucible. The molybdenum alloy, having an oxygen content of not more than 50 ppm, comprising 0.2 to 1.5% of a carbide by wight and the balance, molybdenum, wherein the carbide is at least one selected from titanium carbide, hafnium carbide, zirconium carbide, and tantalum carbide, and a part of the carbides has an aspect ratio of not less than 2.