3D Printed Cermet Porosity Reduction via Pre-Sintering
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Solution Overview
Problem
Three-dimensional printing of cermet and cemented carbide materials faces challenges in achieving a homogeneous structure and minimal porosity due to the use of pre-sintered powders, which can lead to defects like porosity and abnormal grain growth, and powders with high fine fractions compromise flowability and handling.
Innovation Solution
A method involving the use of pre-sintered powders with controlled particle size distribution, a holding step at a specific temperature before liquid phase sintering, and subsequent high-pressure sintering to reduce porosity and ensure even binder distribution, utilizing a process that includes debinding, liquid phase sintering, and high-pressure steps to produce a dense and homogeneous cermet or cemented carbide body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pre-sintered powders are used for 3D printing, then the green body can be formed successfully, but the sintered body exhibits defects such as porosity and abnormal grain growth
Solution Approach 1:
The invention applies preliminary action by conducting a holding step at solid state sintering temperature (1200-1300°C) for 30-500 minutes before the liquid phase sintering step. This pre-treatment modifies the pre-sintered powder particles, making them more receptive to subsequent liquid phase sintering, thereby achieving homogeneous microstructure and minimal porosity while maintaining ease of green body formation
Solution Approach 2:
The invention changes the temperature parameter by introducing a holding step at solid state sintering temperature (1200-1300°C) before liquid phase sintering. This parameter change transforms the powder particle characteristics, enabling better densification and microstructure control during subsequent sintering, thus resolving the contradiction between ease of manufacture and manufacturing precision
2Manufacturing precision
If powder with large fraction of fines is used, then porosity after sintering is reduced, but flowability and handling become problematic
Solution Approach 1:
The holding step at solid state sintering temperature performs a preliminary action on the powder particles, modifying their surface characteristics and internal structure. This pre-treatment enables effective densification during liquid phase sintering without requiring a high fraction of fine particles, thus maintaining both porosity reduction and good powder flowability
Solution Approach 2:
The invention changes the thermal processing parameters by introducing a holding step at solid state sintering temperature before liquid phase sintering. This parameter change achieves porosity reduction through controlled densification rather than relying on fine powder fractions, thereby maintaining powder flowability and handling characteristics
3Manufacturing precision
If sinter-HIP process is used, then porosity is reduced and good cermet material is obtained, but high demands are placed on powder quality
Solution Approach 1:
The invention changes the sintering process parameters by introducing a holding step at solid state sintering temperature (1200-1300°C) for 30-500 minutes before liquid phase sintering. This modified thermal regime achieves effective porosity reduction and homogeneous microstructure with standard pre-sintered powders, eliminating the need for high-quality powder specifications required by sinter-HIP processes
Solution Approach 2:
The holding step performs a preliminary action on the green body by conducting solid state sintering before liquid phase sintering. This pre-treatment prepares the material structure for effective densification during liquid phase sintering, achieving porosity reduction comparable to sinter-HIP but with relaxed powder quality requirements
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 results in a cermet or cemented carbide body with reduced porosity and improved microstructure, maintaining the hardness and toughness characteristic of these materials while minimizing defects and handling issues associated with fine powders.
Implementation Method 1
a holding step prior to the liquid phase sintering step, wherein the duration of the holding step is between 30 and 500 minutes and the temperature for the holding step is between 1200 and (Tm−10)° C.
Implementation Method 2
sintering said green body in a sintering process comprising a liquid phase sintering step at a temperature for liquid phase sintering
Data Source
AI summary
A method of making a 3D printed cermet or cemented carbide body including a hard phase and a metallic binder phase whereby the 3D printed green body is subjected to a sintering process including a holding step prior to a liquid phase sintering step. The sintered bodies have a reduced porosity.