Metal Powder Composition for Additive Manufacturing Crack Reduction
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Solution Overview
Problem
Current metal additive manufacturing techniques face challenges in producing objects with reduced cracks and warpage while maintaining heat resistance, due to limitations in temperature control and residual tensile stress, especially with high-carbon heat-resistant steels that can result in increased residual stress and cracking.
Innovation Solution
A metal powder composition is developed with specific elemental ranges (C, Si, Mn, Cr, Ni, Mo, V, Al, and N) and optimized to satisfy expressions that control the martensite transformation start and finish points, ensuring reduced residual tensile stress and enhanced heat resistance, allowing for objects with less distortion and cracks during additive manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high-carbon heat-resistant steel is used to enhance heat resistance, then heat resistance is improved, but residual tensile stress and cracking increase
Solution Approach 1:
The patent applies parameter changes by precisely controlling the carbon content within 0.05-0.45 mass% and adjusting the ratios of alloying elements (Cr: 7-21 mass%, Ni: 1.5-7 mass%, Mo: 0.1-1.5 mass%, Mn: 0.5-2 mass%) to optimize the material properties. This controlled composition adjustment resolves the contradiction by finding the optimal balance between heat resistance and crack prevention
Solution Approach 2:
The patent creates a composite material system by combining multiple alloying elements in specific proportions. The synergistic effect of Cr, Ni, Mo, Mn, and C creates a material that achieves both heat resistance and reduced residual stress, resolving the contradiction between these two properties
2Shape
If laser beam irradiation is used to melt and solidify powder layer, then complex three-dimensional shapes can be formed, but residual tensile stress is generated on the upper surface
Solution Approach 1:
The patent uses parameter changes by controlling the martensite transformation temperature range (Ms point) through composition adjustment. By ensuring Ms is within 50-280°C and controlling the Creq/Nieq ratio, the material undergoes controlled phase transformation during manufacturing that generates compressive stress to counteract the tensile stress from rapid cooling, while maintaining the ability to form complex shapes
3Productivity
If rapid cooling is performed after solidification, then manufacturing efficiency is improved, but distortion increases due to tensile stress
Solution Approach 1:
The patent exploits phase transitions by designing the material composition to undergo martensite transformation during cooling. The controlled phase change from austenite to martensite generates volume expansion that compensates for thermal shrinkage, reducing distortion while maintaining rapid cooling rates for high productivity
Solution Approach 2:
The patent applies thermal expansion principles by utilizing the volume expansion that occurs during martensite transformation. This transformation expansion counteracts the thermal contraction during rapid cooling, thereby reducing overall distortion and improving manufacturing precision without sacrificing cooling speed
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 optimized metal powder composition effectively reduces distortion and cracking in additively manufactured objects by controlling the martensite transformation, maintaining suitable Ms points within the apparatus' temperature range and enhancing heat resistance through optimized elemental balances.
Implementation Method 1
since volume expansion occurs when the solidified layer undergoes martensite transformation, the volume shrinkage that occurs during the cooling of the solidified layer and the resulting tensile stress are reduced
Implementation Method 2
a method of repeating a step of forming a thin powder layer made of a metal powder and a step of locally melting and solidifying the powder layer by irradiation with an energy beam such as a laser beam or an electron beam
Implementation Method 3
The SLM additive manufacturing method has an advantage that a complicated three-dimensional shape can be easily formed simply by changing an irradiation position of the laser beam
Implementation Method 4
In the case where additive manufacturing is performed by using an SLM 3D printer, only the upper surface of the manufactured object is rapidly heated, so residual tensile stress is generated on the upper surface of the manufactured object after cooling
Data Source
AI summary
The present invention relates to a metal powder containing: 0.001 mass %≤C≤0.45 mass %, 0.01 mass %≤Si≤3.50 mass %, Mn≤2.0 mass %, 7.5 mass %≤Cr≤21.0 mass %, 1.5 mass %≤Ni≤7.0 mass %, Mo≤1.3 mass %, 0.05 mass %≤V≤2.0 mass %, Al≤0.015 mass %, and N≤0.20 mass %, with the balance being Fe and unavoidable impurities, satisfying 0.05 mass %≤C+N≤0.58 mass %, and satisfying: 10<15C+Mn+0.5Cr+Ni<20 and Creq/Nieq<5.6, where Creq=Cr+Mo+1.5Si+0.5Nb, and Nieq=Ni+30C+30N+0.5Mn.