⚡ electrical engineering

Systematic Identification and Multi-Criteria Selection of an Optimal Laser Powder Bed Fusion Metal for a High-Pressure Die-Casting Mould with Conformal Cooling Channels

This paper presents a systematic, end-to-end methodology combining a PRISMA-compliant bibliometric review with a two-stage multi-criteria decision-making framework to identify 18Ni300 maraging steel as the optimal laser powder bed fusion material for high-pressure die-casting moulds with conformal cooling channels.

Original authors: Dawit Berhanu Kebede, Ominigho Benedict Otanocha

Published 2026-08-03

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CC BY 4.0

Original authors: Dawit Berhanu Kebede, Ominigho Benedict Otanocha

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine you are baking a giant, intricate cake, but instead of flour and sugar, you are pouring molten aluminum into a mold. This process, called high-pressure die casting, is how the world makes everything from car engine blocks to smartphone cases. The trickiest part isn't just pouring the metal; it's cooling it down fast and evenly. If the mold gets too hot in one spot, the cake (or car part) warps, cracks, or gets stuck. For decades, engineers have used metal molds with straight, drilled holes for cooling water, like a maze of tunnels that can't quite reach every nook and cranny of the cake. But what if you could print the mold itself, layer by layer, with cooling channels that snake perfectly around the shape of the product? That's the magic of "conformal cooling" made possible by a high-tech printer called Laser Powder Bed Fusion (LPBF). It's like having a 3D printer that can build a mold with a built-in, custom-fit air conditioning system.

However, there's a catch. To print these complex molds, you need a special metal powder. This metal has to be a superhero: it must be strong enough to handle the heat of molten aluminum, tough enough to survive being heated and cooled thousands of times without cracking, and conductive enough to suck the heat away quickly. But here's the problem: metals that are great at conducting heat (like copper) are often too soft or brittle to print into complex shapes. Metals that are easy to print (like some aluminum alloys) melt too easily when they touch the molten aluminum. So, engineers are stuck trying to find the "Goldilocks" metal—one that isn't too hard, not too soft, and just right for the job.

This paper is essentially a massive, super-organized treasure hunt to find that perfect metal. The authors didn't just guess; they looked at thousands of scientific studies from the last few years to see which metals scientists are talking about the most. Then, they set up a rigorous "tournament" to test them. They created a scoring system that checked if a metal could survive the heat, if it could be printed without breaking, how much it costs, and how well it cools things down. They even built a safety net to make sure they didn't accidentally pick a metal that looked great on paper but would fail in the real world.

After running the numbers, the paper rules out several popular contenders. Aluminum alloys like AlSi10Mg and Scalmalloy were kicked out because they would melt under the heat of the molten aluminum. A shape-memory alloy called NiTi was rejected because it's too squishy to hold its shape under pressure. Even pure tungsten, which is amazing at conducting heat, was disqualified because it's so brittle that it would crack the moment you tried to print it into a complex shape.

The winner of this metal tournament is 18Ni300 maraging steel. Think of it as the ultimate all-rounder. It's strong enough to handle the heat, tough enough to be printed into those fancy, winding cooling channels, and it conducts heat well enough to keep the mold cool. The authors are very confident in this choice; they ran the same test with different rules and weights, and 18Ni300 kept coming in first place every single time. They even tested it against the old-school "champions" of the industry (like H13 steel and copper alloys), and those traditional materials failed the specific tests needed for this new printing technology. So, if you want to build the next generation of super-efficient metal molds, the paper suggests that 18Ni300 maraging steel is the material to use.

Technical Summary: Systematic Identification and Multi-Criteria Selection of an Optimal Laser Powder Bed Fusion Metal for a High-Pressure Die-Casting Mould with Conformal Cooling Channels

Problem Statement
High-pressure die casting (HPDC) is critical for manufacturing complex, thin-walled components, yet productivity and part quality are limited by the thermal management capabilities of the mould. While conformal cooling channels (CCCs) fabricated via Laser Powder Bed Fusion (LPBF) offer significant advantages in cycle time reduction and thermal uniformity compared to conventional straight-drilled channels, their successful implementation is constrained by material selection. The ideal parent material must simultaneously satisfy a matrix of antagonistic requirements: high thermal conductivity for efficient heat extraction, exceptional thermomechanical fatigue resistance to withstand cyclic contact with molten aluminium (~660–700 °C), robust LPBF processability to ensure defect-free complex geometries, and economic viability. Existing literature often relies on historical precedent rather than systematic evidence, and conventional Multi-Criteria Decision Making (MCDM) frameworks frequently employ purely compensatory aggregation, allowing a high score in one area (e.g., thermal conductivity) to mask critical failures in others (e.g., printability or melting point).

Methodology
The study proposes a reproducible, end-to-end pipeline combining bibliometric analysis with a two-stage MCDM framework:

Systematic Candidate Identification (PRISMA 2020):
- A bibliometric review of 22,312 records from Web of Science and Scopus (2021–2025) was conducted to identify the most investigated single-grade LPBF metals.
- A dictionary-based text-mining algorithm extracted material grades, resulting in a top-10 candidate list dominated by Ti-6Al-4V, AlSi10Mg, 316L SS, Inconel 718, NiTi, Inconel 625, Scalmalloy, Pure Tungsten, 18Ni300 maraging steel, and 17-4PH SS.
- To address bibliometric blind spots (e.g., under-representation of conventional tool steels H13/Dievar due to printability issues, and copper alloys due to grade fragmentation), industry benchmarks were deliberately "force-included" for validation.
Two-Stage MCDM Framework:
- Stage 1: Non-Compensatory Feasibility Screen: A strict "knock-out" filter was applied to eliminate materials that fail fundamental physical constraints. Thresholds were set for HPDC compatibility ( $\tau_{HPDC} \ge 3$ ) and LPBF manufacturability ( $\tau_{manuf} \ge 4$ ). This stage prevents the mathematical compensation of a critical failure (e.g., a material melting below the casting temperature) by a high score in another criterion.
- Stage 2: Compensatory Ranking (AHP-TOPSIS):
  - AHP (Analytic Hierarchy Process): Six criteria were weighted: Technical Performance, Sustainability, LPBF Manufacturability, Cost-effectiveness, HPDC Mould Compatibility, and Thermal Efficiency. Pairwise comparisons yielded a consistent weight vector ($CR = 0.019$), prioritizing HPDC compatibility (41.6%) and Thermal Efficiency (26.5%).
  - TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution): The remaining feasible candidates were ranked based on their geometric distance from the ideal solution.
- Robustness Verification: The selection was validated through Pareto dominance analysis, sensitivity analysis across six weighting scenarios (including equal weights and single-criterion prioritization), and threshold variation tests.

Key Results

Screening Outcomes: The feasibility screen eliminated four candidates: AlSi10Mg, NiTi, and Scalmalloy (failed HPDC compatibility due to low melting points or lack of structural stability) and Pure Tungsten (failed manufacturability due to brittleness and cracking).
Optimal Selection: Among the six feasible candidates, 18Ni300 maraging steel emerged as the optimal material with a TOPSIS closeness coefficient of 0.957.
- It achieved the highest balance of technical performance, manufacturability, and HPDC compatibility among printable steels.
- Crucially, it offered the highest thermal conductivity (~21 W·m⁻¹·K⁻¹ after ageing) among the feasible set, directly supporting the CCC objective.
Ranking Stability: 18Ni300 retained the Rank 1 position across all six weighting scenarios, including an equal-weight scenario where the margin over the second-best candidate (17-4PH stainless steel) was narrowest but still positive.
Benchmark Validation: When conventional benchmarks (H13, Dievar, CuCrZr) were force-included, they were rejected by the Stage 1 screen: H13 and Dievar failed on manufacturability (cracking susceptibility), and CuCrZr failed on HPDC compatibility (softening/soldering). This confirmed that the selection of 18Ni300 is robust and not an artifact of the initial candidate set composition.

Significance and Claims
The paper claims to provide the first fully reproducible pipeline that moves from systematic literature identification to a defensible material decision for LPBF HPDC moulds. Its primary contributions are:

Methodological Rigor: The integration of a non-compensatory feasibility screen prior to compensatory ranking is highlighted as essential to prevent the selection of physically unviable materials (demonstrated by the erroneous ranking of Pure Tungsten as "optimal" if the screen were omitted).
Evidence-Based Selection: The study replaces historical precedent with a data-driven approach, utilizing a PRISMA-compliant review of over 22,000 records to define the candidate pool.
Robustness: The selection of 18Ni300 is shown to be invariant to variations in weighting schemes, screening thresholds, and the inclusion of conventional tooling materials.
Practical Recommendation: The study concludes that 18Ni300 maraging steel is the recommended parent material for HPDC conformal cooling applications, offering a viable compromise between thermal efficiency, mechanical durability, and printability.

The authors note that while the 1–10 scoring involves expert judgment, the robustness of the result is ensured by the dominance pre-check and sensitivity analyses, which demonstrate that the outcome relies on the inherent properties of the feasible set rather than specific subjective weights. Future work is identified as the development of LPBF-optimized hot-work tool steels to potentially expand the feasible candidate set in the future.

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