Titanium Powder Nitride Coating to Limit Surface Oxidation
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Solution Overview
Problem
Active metal powders, particularly titanium and titanium alloys, face issues of natural oxidation of the surface layer due to increased oxygen concentration, which limits reuse and affects the properties of the powder, especially when fine particle sizes are required for molding methods like lamination and injection molding.
Innovation Solution
A surface modification method using a reactive fluid to form a thin nitrogen-containing coating, primarily Ti2N, on active metal particles, inhibiting oxidation by controlling heat and movement to maintain a low nitrogen diffusion into the particles, while ensuring the powder retains its characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the particle size of active metal powder is decreased to satisfy molding requirements, then the powder can be used for lamination molding and injection molding, but the surface layer naturally oxidizes more easily and oxygen concentration increases
Solution Approach 1:
The patent converts the harmful oxidation process into a beneficial nitridation process by introducing nitrogen-containing fluid. Instead of preventing surface reaction entirely, it directs the reaction toward forming protective nitrogen compounds (Ti2N, TiN) that inhibit further oxidation, thus converting the harmful effect of surface reactivity into a protective mechanism
Solution Approach 2:
The patent changes the chemical composition parameters of the surface layer by controlling nitrogen content (0.01-6.0 mass%) and forming specific nitride phases. By adjusting these compositional parameters, the surface properties are modified to achieve oxidation resistance while maintaining the desired particle size for molding applications
2Object-affected harmful factors
If a nitride coating is formed to inhibit oxidation, then the surface layer is protected, but nitrogen content increases which may affect titanium properties
Solution Approach 1:
The patent applies local quality by concentrating the nitrogen content primarily in the surface layer rather than uniformly throughout the bulk material. The surface layer contains nitrogen (0.01-6.0 mass%) forming protective nitride compounds, while the core titanium particles maintain their original properties. This localized approach provides oxidation resistance where needed without significantly affecting the overall nitrogen content and bulk material properties
3Productivity
If the active metal powder is reused multiple times, then production efficiency increases, but the surface layer accumulates oxygen and becomes unusable
Solution Approach 1:
The patent applies preliminary anti-action by pre-forming a nitrogen-containing protective layer on the surface before oxidation can occur during reuse. This pre-established barrier (with nitrogen content 0.01-6.0 mass% and specific nitride phases) proactively prevents oxygen from penetrating and accumulating in the surface layer, thereby maintaining powder usability across multiple reuse cycles
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 effectively reduces natural oxidation of the surface layer, maintains the powder's properties, and allows for safer handling and increased reuse, with improved fluidity and reduced ignition risk, making it suitable for molding applications.
Implementation Method 1
the surface layer of the active metal particles in the active metal powder reacts with an arbitrary component in the fluid by the heat, the surface layer is modified
Implementation Method 2
heat is generated by moving the active metal powder in the fluid
Implementation Method 3
the surface layer is modified... and the surface layer can be hardly naturally oxidized
Data Source
AI summary
Active metal particles in which the surface layer is hardly oxidized and a method for producing the active metal particles is provided. In the method for modifying the surface of active metal particles, heat is generated by moving active metal powder in a fluid, and the surface layer of the active metal particles is reacted with an arbitrary component in the fluid by the heat to modify the surface layer. Preferably, moving the active metal powder draws a substantially circular orbit while vibrating. A vibrating mill is preferably used when making such movement with respect to the active metal powder. Then, the powder obtained by the surface modification has a nitrogen-containing coating as a surface layer with a thickness more than 1 nm and less than or equal to 6 nm. The powder has a fluidity in the range of 25 seconds/50 g or more and 45 seconds/50 g or less.