Fe-Based Alloy for Additive Manufacturing Crack Resistance
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Solution Overview
Problem
Existing Fe-based alloys for melting-solidification shaping, such as those used in additive manufacturing, tend to crack due to thermal stress and have insufficient toughness, while high-hardness alloys like Co-based and Ni-based superalloys are difficult to work with and costly.
Innovation Solution
An Fe-based alloy with a composition of 18.0-25.0 mass% Co, 12.0-20.0 mass% (Mo+W)/2, 0.2-5.0 mass% Mn, and 0.5-10.0 mass% Ni, along with optional elements, is developed to stabilize the austenite phase and inhibit ferrite precipitation, ensuring a high-hardness overlay weld layer with reduced cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-hardness alloys like Co-based and Ni-based superalloys are used, then wear resistance is improved, but workability deteriorates and cost increases
Solution Approach 1:
The patent changes the compositional parameters by using Fe-based alloy instead of Co-based or Ni-based superalloys, with specific control of Co content (18.0-25.0 mass%), Mo content (12.0-20.0 mass%), and addition of Mn (0.2-5.0 mass%) and Ni (0.5-10.0 mass%). This parameter change achieves high hardness and wear resistance while improving workability and reducing cost.
Solution Approach 2:
The patent creates a composite microstructure consisting of martensite phase and retained austenite phase, with fine precipitates formed during aging treatment. This composite structure provides both high hardness/wear resistance and improved toughness/workability, resolving the contradiction between wear resistance and workability.
2Ease of manufacture
If alloy powder is used for additive manufacturing, then shaping capability is improved, but cracking occurs due to thermal stress and insufficient toughness
Solution Approach 1:
The patent adjusts compositional parameters including Co content (18.0-25.0 mass%), Mo content (12.0-20.0 mass%), Mn content (0.2-5.0 mass%), and Ni content (0.5-10.0 mass%) to control phase transformation behavior during rapid cooling. These parameter changes ensure adequate martensite formation and prevent cracking while maintaining shaping capability.
Solution Approach 2:
The patent incorporates Mn and Ni elements in advance during alloy composition design to stabilize austenite phase and prevent premature ferrite precipitation. This preliminary action ensures that the microstructure remains suitable for high toughness and crack resistance even after rapid cooling during additive manufacturing, preventing cracking before it occurs.
3Strength
If Co content is increased to achieve high hardness, then wear resistance is improved, but cost increases due to poor availability
Solution Approach 1:
The patent optimizes Co content to a specific range (18.0-25.0 mass%) rather than using high Co content. Combined with Mo (12.0-20.0 mass%), Mn (0.2-5.0 mass%), and Ni (0.5-10.0 mass%), this parameter optimization achieves high hardness and wear resistance while reducing dependency on expensive Co, thereby lowering cost.
Solution Approach 2:
The patent creates a composite strengthening mechanism where Co, Mo, Mn, and Ni work together to form martensite and retained austenite phases with fine precipitates. This composite approach allows achieving high hardness through multiple elements rather than relying solely on high Co content, reducing cost while maintaining performance.
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 alloy achieves a high-hardness overlay weld layer with improved toughness by regulating Co content and adding Ni and Mn, preventing ferrite precipitation and ensuring adequate µ phase formation, thus reducing the likelihood of cracking during melting-solidification shaping processes.
Implementation Method 1
regulating Co content and adding Ni and Mn, preventing ferrite precipitation and ensuring adequate µ phase formation
Implementation Method 2
a structure is formed through rapidly-cooling-solidification
Implementation Method 3
in cases when an alloy powder having such a composition is subjected to additive manufacturing and the resultant shaped article is subjected to an aging treatment at from 400 to 700°C, then a hardness required of wear-resistant members is obtained
Data Source
Figure 1~2
AI summary
An Fe-based alloy for melting-solidification shaping including, in mass%: 18.0 ≤ Co < 25.0; 12.0 ≤ Mo + W/2 ≤ 20.0; 0.2 ≤ Mn < 5.0; 0.5 ≤ Ni ≤ 10.0; and 0 ≤Si ≤ 1.0, with the balance being Fe and unavoidable impurities, and satisfying the following expressions (1) and (2) when [M] represents a content of an element M expressed in mass% basis, 58 ≤ [Co] + 3([Mo] + [W]/2) ≤ 95 (1), A/B ≥ 1.6 (2) where A = [Co] + [Ni] + 3[Mn], and B = [Mo] + [W]/2 + [Si], in which when the Fe-based alloy includes no Mo, the expressions (1) and (2) are calculated using [Mo] = 0, when the Fe-based alloy includes no Si, the expression (2) is calculated using [Si] = 0, and when the Fe-based alloy includes no W, the expressions (1) and (2) are calculated using [W] = 0.