Metal Powder with Thin Coating for Low-Temperature Sintering
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Solution Overview
Problem
Three-dimensional printing of metal articles faces challenges with high sintering temperatures, leading to temperature gaps and insufficient binding strength, causing collapse or partial collapse of parts, especially with metals like Fe, Ni, Cu, and Ti alloys that sinter above 1000°C.
Innovation Solution
Using metal particles with a metal core and a thin metal layer, where the thin metal layer has a lower melting temperature than the core, allowing for reduced fusing temperatures and improved binding strength through diffusion alloys formed during the printing process, which can be achieved by applying external energy to the binder fluid containing metal oxide nanoparticles and a reducing agent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high sintering temperatures (above 1000°C) are used to sinter metal particles, then metal particles can be fused together, but binding strength is insufficient and parts collapse
Solution Approach 1:
A binder fluid containing metal oxide nanoparticles and a reducing agent is introduced as an intermediary substance between the metal particles. The binder fluid forms binding bridges that hold particles together at lower temperatures, mediating the bonding process before final sintering occurs.
Solution Approach 2:
The invention changes the chemical state of the binding material by using metal oxide nanoparticles that are reduced in situ to metallic form. This parameter change (from oxide to metal) enables the binder to effectively bond metal particles at lower temperatures than traditional sintering methods.
2Reliability
If metal particles with high melting points are used, then desired metal properties are achieved, but temperature gap between binder decomposition and sintering increases
Solution Approach 1:
The binder material parameters are changed by using metal oxides with controlled reduction temperatures. The reducing agent transforms the metal oxide binder into metallic form at temperatures below the metal particle sintering point, effectively closing the temperature gap between binder decomposition and particle sintering.
Solution Approach 2:
The reduction of metal oxide binder and the sintering of metal particles occur in a continuous process without interruption. The binder remains effective throughout the heating process, providing continuous binding action from low temperature through to the final sintering temperature.
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
This approach enables the formation of robust and sturdy metal parts at lower temperatures, reducing the risk of collapse and enhancing mechanical bonding between metal particles, while maintaining the desired shape and density of the printed object.
Implementation Method 1
the metal material of the thin metal layer can in-diffuse into the metal core forming a diffusion alloy having a lower melting temperature than the metal core
Implementation Method 2
the metal oxide nanoparticles can be reduced by the reducing agent when external energy is applied to the binder fluid
Implementation Method 3
three-dimensional printing of metal articles can involve heating metal powder in order to sinter or melt metal particles to form a fused article
Implementation Method 4
heating metal powder in order to sinter or melt metal particles
Data Source
AI summary
The present disclosure is drawn to a material set including a powder bed material and a binder fluid. The powder bed material can be from 80 wt % to 100 wt % metal particles having a metal core and a thin metal layer on the core, and the metal particles having a D50 particle size distribution value ranging from 4 μm to 150 μm and the thin metal layer having an average thickness from 20 nm to 2 μm. The binder fluid can adhere a first portion of the powder bed material relative to a second portion of the powder bed material not in contact with the binder fluid.