SX500 Superalloy: SpaceX’s Single-Crystal Metal for Raptor Engines

In the relentless pursuit of fully reusable, deep-space rocket propulsion, SpaceX pushed traditional aerospace engineering to its absolute limits, ultimately necessitating the creation of an entirely new class of materials. Enter the SX500 superalloy—a proprietary, single-crystal nickel-based metal engineered specifically to survive the punishing interior of the Raptor engine. Operating inside ultra-high-pressure, oxygen-rich environments that would instantly ignite or melt conventional aerospace metals, SX500 represents a monumental leap in metallurgy. By combining a monocrystalline structure, advanced refractory elemental additions, and state-of-the-art manufacturing techniques, this alloy forms the backbone of SpaceX's high-performance turbopumps and preburners, transforming how humanity reaches for the stars.

The relentless pursuit of reusable, high-efficiency space transportation has driven private aerospace engineers to push materials science far beyond traditional industrial boundaries.

At the vanguard of this metallurgical revolution is the sx500 superalloy, a proprietary material engineered by SpaceX specifically to solve the extreme thermal and chemical challenges of the Raptor rocket engine. As modern aerospace designs demand higher chamber pressures and greater thrust-to-weight ratios, standard commercial metals frequently fall short, buckling under the combined stress of intense heat, corrosive gases, and mechanical fatigue. The development of SX500 represents a major paradigm shift, moving away from off-the-shelf alloys toward highly customized material solutions tailored to the brutal realities of methane-fueled, full-flow staged combustion engines.

To understand why a specialized formulation like SX500 is necessary, it is helpful to examine the fundamental distinction between a conventional alloy and a true superalloy. A standard alloy is typically a metallic mixture composed of two or more elements—such as steel, which combines iron and carbon—designed to improve basic strength or corrosion resistance over pure metals. In contrast, a superalloy is an advanced metallic compound, usually based on nickel, cobalt, or iron, specifically formulated to operate at high fractions of its absolute melting point while maintaining exceptional mechanical strength, surface stability, and resistance to creep and oxidation. While traditional alloys suffice for structural frames and lower-temperature hardware, superalloys are the undisputed backbone of modern aerospace propulsion, enabling components to function reliably in environments where lesser materials would rapidly soften, deform, or disintegrate.

SpaceX has pushed the boundaries of aerospace engineering by developing specialized materials tailored to the brutal demands of next-generation propulsion systems.

At the core of this metallurgical innovation is SX500, a proprietary single-crystal, nickel-based superalloy engineered specifically for the company's Raptor rocket engines. Unlike off-the-shelf commercial metals, SX500 was designed from the ground up to address the extreme thermal and mechanical stresses encountered inside reusable, high-performance methane-fueled engines. Traditional aerospace alloys often fall short when subjected to the combined forces of cryogenic propellants, blistering combustion temperatures, and unprecedented chamber pressures, necessitating a completely new class of material.

SX500 serves as a critical, advanced alternative to conventional materials for constructing highly stressed Raptor engine components. Among these applications are intricately shaped cast manifolds and heavy-duty turbopumps that must operate continuously under severe conditions without degrading. By replacing standard aerospace grades with this advanced single-crystal formulation, SpaceX can achieve higher thrust-to-weight ratios and ensure the reliability required for rapid rocket reusability.

Through the deployment of SX500, SpaceX bridges the gap between theoretical metallurgy and practical, high-frequency aerospace manufacturing.

To fully appreciate the engineering achievement represented by proprietary materials like SX500, it is first necessary to distinguish standard metallic alloys from the specialized category known as superalloys.

A standard metal alloy is created by combining a primary metal with one or more other metallic or non-metallic elements to improve basic mechanical properties such as tensile strength, hardness, or corrosion resistance. Common examples include structural carbon steels and standard aluminum alloys used in automotive manufacturing and general construction. While these conventional materials perform admirably under moderate conditions, their mechanical strength degrades rapidly as temperatures climb, typically losing structural integrity well below half of their absolute melting points. They are fundamentally unsuited for the searing environments found inside modern gas turbines or rocket propulsion systems.

In contrast, superalloys represent the pinnacle of metallurgical engineering. These advanced metallic materials are specifically designed to operate for extended periods at very high fractions of their absolute melting points, frequently exceeding 0.7 to 0.8 of their solidus temperature. Superalloys exhibit exceptional mechanical strength, extraordinary resistance to thermal creep deformation under high mechanical stress, superior surface stability, and high resistance to oxidation and corrosion. This unique combination of properties is achieved through complex chemical compositions—often based on nickel, cobalt, or iron—and intricate microstructures that prevent atomic diffusion and grain boundary sliding at extreme temperatures.

Within the aerospace and power generation industries, several established superalloys have long served as the baseline for high-temperature applications. Alloys such as Hastelloy, Waspaloy, and the various proprietary René alloys developed for commercial jet engines and industrial gas turbines rely heavily on complex solid-solution strengthening and precipitation hardening. These materials utilize carefully balanced additions of chromium, cobalt, molybdenum, tungsten, aluminum, and titanium to form stable intermetallic precipitates, such as the gamma-prime phase, which effectively lock dislocation movements. However, even these high-performance industry standards face strict operational limits when pushed into the ultra-high-pressure, oxygen-rich environments characteristic of next-generation full-flow staged combustion rocket engines, paving the way for revolutionary materials like SpaceX's SX500.

Understanding these foundational differences clarifies why conventional metallurgy falls short in extreme aerospace applications and highlights the necessity for advanced materials engineered at the atomic level.

Exploring how this revolutionary material redefines the limits of high-performance engineering requires a closer look at its unique development history and the underlying metallurgical mechanics that set it apart from legacy metals.

Pushing the boundaries of chemical propulsion requires mastering environments of unimaginable heat and pressure, a challenge that pushed conventional aerospace metallurgy to its absolute limits.

Inside a modern full-flow staged combustion rocket engine like SpaceX's Raptor, the operational physics are exceptionally brutal. Fuel and oxidizer are fed through complex turbomachinery into combustion chambers operating at pressures that eclipse anything seen in traditional aerospace applications. While legacy rocket engines typically operated at pressures around 100 to 200 bar, the Raptor engine pushes operational pressure past the unprecedented threshold of 800 bar, equivalent to roughly 800 atmospheres or 12,000 pounds per square inch. At these extreme pressures, fluid dynamics and chemical kinetics behave in ways that can easily trigger structural failure in standard materials.

Compounding this high-pressure challenge is the engine's use of oxygen-rich preburners. To maximize efficiency and power output, the Raptor routes nearly pure, high-pressure liquid oxygen through its preburner stage before injecting it into the main combustion chamber. In this zone, oxygen concentrations soar to roughly 4,000 times standard sea-level levels. This creates an environment exponentially more aggressive and destructive than an industrial oxyacetylene cutting torch. Under such conditions, standard aerospace metals do not merely oxidize; they spontaneously ignite and burn fiercely in the high-pressure oxygen stream, leading to instant catastrophic failure.

The heart of SpaceX's Raptor engine relies on an aggressive combustion cycle that pushes material science to its absolute limits.

At the core of this engineering marvel is the oxygen-rich staged combustion cycle, designed to maximize efficiency and thrust. Within this architecture, the oxygen-rich preburner stage plays a critical role by pumping liquid oxygen directly into high-pressure combustion chambers. This process operates under extreme operational pressures exceeding 800 bar, which equates to roughly 800 atmospheres or an astonishing 12,000 psi. Maintaining structural integrity and reliable fluid dynamics under such immense mechanical stress requires materials that do not deform, fatigue, or fail.

Compounding the severe pressure requirements, the chemical environment inside the preburner is intensely reactive. Oxygen concentrations in this zone reach a staggering 4,000 times normal sea-level levels. This creates an extraordinarily hostile gaseous environment that far exceeds the severity of an industrial oxyacetylene cutting torch. Under these punishing conditions, traditional aerospace metals would instantly ignite, flare, and undergo catastrophic combustion, effectively consuming themselves in seconds.

It is precisely this brutal intersection of ultra-high pressure and hyper-concentrated oxygen that necessitated the creation of proprietary solutions like the SX500 superalloy.

Operating in an environment where standard aerospace metals turn into instantaneous fuel demands entirely new paradigms in material science.

When dealing with high-pressure gaseous oxygen, the rules of metallurgy fundamentally shift. In standard atmospheric conditions, metals oxidize at controlled rates, often forming protective surface layers. However, when oxygen pressures climb to extreme levels, the chemical activity of the gas increases exponentially. At elevated temperatures and pressures, the thermodynamic driving force for oxidation becomes so aggressive that almost any traditional metal or alloy will spontaneously ignite and burn violently. This phenomenon, known as oxygen-promoted combustion or metal burning, transforms structural components from load-bearing machinery into a self-consuming heat source in a matter of milliseconds.

To survive this relentless chemical assault, the sx500 superalloy relies on the rapid formation of a stable, highly adherent, and passivating oxide layer. As soon as the material is exposed to the oxygen-rich preburner environment, specific refractory and alloying elements within the single-crystal matrix react with the gas to grow an ultra-thin, impenetrable ceramic-like barrier. This passivating scale acts as a molecular shield, starving the underlying metal of oxygen and halting further oxidation kinetics. Unlike conventional alloys whose protective scales might crack, spall, or dissolve under thermal and mechanical stress, the SX500 oxide layer remains chemically intact and self-healing even amidst severe operational vibrations and extreme pressure fluctuations.

Preventing flaring and catastrophic ignition also requires mitigating the risk of stress corrosion cracking and localized hot-spot burn-through. In typical high-pressure rocket turbopumps, microscopic surface defects or micro-fissures can concentrate stress and expose fresh, unoxidized metal to the high-velocity oxidant stream, sparking an uncontainable chain reaction. Because SX500 is engineered as a single-crystal structure free of grain boundaries, it eliminates the preferential pathways usually exploited by high-temperature oxidation and embrittlement. By pairing this advanced monocrystalline architecture with its robust passivating oxide chemistry, SX500 successfully resists the extreme environment of the Raptor preburner, ensuring structural integrity and preventing catastrophic engine failures where conventional alloys would be instantly consumed.

The ability of the SX500 superalloy to maintain a stable, passivating oxide barrier under extreme pressures is what ultimately bridges the gap between theoretical rocket design and reusable, high-performance space flight.

To survive this relentless onslaught of heat, pressure, and high-concentration oxidizers without succumbing to metal fires, engineers needed to understand the precise mechanics of why standard alloys fail and how specialized protective behaviors can be engineered into the core of the material.

The metallurgical design of SX500 represents a monumental leap in high-temperature engineering, combining precise elemental formulation with advanced microstructural control to survive the most punishing environments in modern rocketry.

At its core, SX500 is a specialized nickel-based superalloy engineered specifically to overcome the physical limitations of standard aerospace metals. Traditional aerospace applications have long relied on standard nickel-chromium alloys, but the sheer thermal and oxidative demands of the SpaceX Raptor engine required a completely fresh approach to metallurgy. By carefully balancing its elemental makeup, metallurgists incorporated high concentrations of refractory elements—such as tungsten, tantalum, and rhenium—into the nickel matrix. These heavy, high-melting-point additions provide exceptional solid-solution strengthening, anchoring the atomic lattice and dramatically reducing thermal softening when operating at temperatures that approach the melting point of the alloy itself.

Beyond its elemental composition, the true mechanical genius of SX500 lies in its monocrystalline architecture. Conventional polycrystalline metals contain microscopic grain boundaries—the interfaces where individual crystal domains meet during solidification. At extreme operating temperatures, these grain boundaries serve as primary sites for atomic diffusion, void formation, and high-temperature creep, ultimately leading to structural deformation or fracture under sustained mechanical stress. By eliminating grain boundaries entirely through specialized crystal growth techniques, SX500 suppresses grain-boundary sliding and limits dislocation movement. The material achieves this stability through dense, finely dispersed ordered intermetallic phases that act as dislocation-pinning obstacles, ensuring dimensional stability and long-term creep resistance under intense centrifugal and pressure loads.

When compared directly against legacy aerospace materials like Inconel 600, Inconel 625, and Inconel 718, SX500 operates in an entirely different performance tier. While standard Inconel alloys are exceptional for general high-temperature ducting, exhaust systems, and moderate-pressure structural components, they suffer from critical vulnerabilities when exposed to ultra-high-pressure, oxygen-rich environments. Inconel variants lack the specialized oxidation barriers and phase stability required to prevent rapid metal combustion under high oxygen partial pressures. SX500 outperforms these conventional alloys by rapidly forming a dense, self-healing, passivating oxide scale that halts further oxygen ingress. As we examine the specific manufacturing techniques used to shape this advanced material, we can better understand how directional solidification and modern additive manufacturing bring these complex metallurgical properties to life in flight-ready Raptor hardware.

At the core of the SX500 superalloy lies a sophisticated metallurgical formulation engineered specifically to conquer the most aggressive thermal and chemical environments in modern rocketry.

The foundation of SX500 is a high-purity nickel matrix, chosen for its exceptional ability to retain structural integrity and face-centered cubic stability across a vast thermal spectrum. Unlike standard structural steels or lower-tier nickel alloys, nickel-based superalloys can accommodate significant amounts of alloying elements into solid solution without destabilizing their crystal lattice. In the case of SX500, this foundational matrix is heavily fortified with strategic refractory additions—such as rhenium, tungsten, tantalum, and molybdenum—which form the primary defense against thermal degradation and high-temperature deformation.

Refractory elements play a multi-faceted role in the survival of the SX500 superalloy inside the Raptor's extreme combustion stages. Heavy atoms like tungsten and rhenium slow down atomic diffusion at elevated temperatures, effectively locking the crystal lattice in place and drastically raising the melting point of the alloy. Furthermore, these additions are critical in suppressing oxygen-promoted combustion. In the high-pressure, oxygen-rich preburners of the Raptor engine, traditional metals act almost as fuel, prone to catastrophic ignition and rapid flaring. SX500 utilizes precise refractory proportions to encourage the formation of a tightly adherent, highly stable passivating oxide scale that stops inward oxygen diffusion.

Designing an alloy for these conditions requires navigating a series of complex metallurgical trade-offs. While heavy refractory additions like rhenium and tungsten provide unmatched burn resistance and high-temperature strength, they also significantly increase the density of the material. In aerospace applications, every gram matters, forcing metallurgists to balance structural survivability against the payload penalties of a heavier engine. Additionally, packing a nickel matrix with high concentrations of refractory elements narrows the processing window, dramatically increasing the risk of freckling, segregation, and casting defects during the directional solidification required to produce a single-crystal component.

Through a careful balance of elemental chemistry and high-performance refractory additions, SX500 achieves a rare synthesis of chemical stability and mechanical durability.

The exceptional performance of the sx500 superalloy under extreme thermal and mechanical stress is fundamentally rooted in its single-crystal metallurgical architecture.

In conventional polycrystalline metals, the internal structure is composed of numerous microscopic crystal grains joined together by boundaries. At elevated temperatures, these grain boundaries become the weakest structural links, serving as primary pathways for atomic diffusion, void formation, and intergranular sliding. When subjected to continuous mechanical loads at high temperatures, standard alloys suffer from creep—the slow, permanent deformation of the material over time. Grain boundaries readily slip and separate under these conditions, eventually leading to structural failure. By eliminating grain boundaries entirely through specialized manufacturing techniques, the sx500 superalloy removes these inherent mechanical vulnerabilities, allowing the material to maintain its structural integrity and dimensional stability under severe operational stress.

Beyond the absence of grain boundaries, the strength of the sx500 superalloy is heavily driven by the presence of ordered intermetallic phases, most notably gamma-prime precipitates. These finely dispersed secondary phases act as microscopic obstacles within the single-crystal matrix. When external mechanical loads attempt to force atomic planes to slide past one another—a process driven by the movement of crystalline defects known as dislocations—the gamma-prime precipitates mechanically block their path. This mechanism, known as dislocation-pinning, effectively locks the crystal lattice in place and prevents plastic deformation. The ordered nature of these intermetallic phases requires dislocations to cut through the precipitates rather than simply bypass them, which demands a significantly higher energy threshold and dramatically increases high-temperature strength.

Furthermore, this advanced microstructural configuration provides superior resistance to thermal fatigue and mechanical degradation during rapid thermal cycling. As components within high-performance rocket engines experience extreme temperature gradients during startup, firing, and shutdown, the lack of anisotropic grain boundary mismatch prevents localized thermal stresses from accumulating. The uniform single-crystal lattice of the sx500 superalloy allows for predictable thermal expansion and contraction, ensuring that components like turbine blades and high-pressure manifolds do not warp, fracture, or experience accelerated creep over repeated operational lifecycles. This combination of dislocation-pinning and a continuous monocrystalline matrix enables the alloy to push the boundaries of modern aerospace engineering.

Through its advanced single-crystal structure and sophisticated phase precipitation, the sx500 superalloy effectively neutralizes the primary failure modes associated with high-temperature metal deformation.

When pushing aerospace propulsion to its absolute limits, traditional nickel-based superalloys often reach their physical boundaries, prompting the development of proprietary alternatives like SX500.

To understand why SpaceX engineered the SX500 superalloy, it is essential to examine the chemical and structural limitations of legacy aerospace materials, particularly the Inconel family. Traditional high-performance alloys such as Inconel 600, 625, and 718 have served as industry standards for decades due to their exceptional corrosion resistance and mechanical strength. The inconel 600 composition relies heavily on a solid-solution nickel-chromium matrix, typically containing around 72 percent nickel and 14 to 17 percent chromium, making it ideal for moderate-temperature industrial applications. Building upon this, the inconel 625 composition introduces molybdenum and niobium into a nickel-chromium base, yielding a robust alloy with approximately 58 percent nickel, 20 to 23 percent chromium, and roughly 8 to 10 percent molybdenum, which provides remarkable resistance to pitting and crevice corrosion.

The engineering landscape shifts further when answering a fundamental metallurgical question: is Inconel 718 a nickel-based superalloy? Yes, Inconel 718 is indeed a precipitation-hardenable nickel-chromium superalloy that forms the backbone of modern aerospace structural design. The standard inconel 718 composition features approximately 50 to 55 percent nickel, 17 to 21 percent chromium, and significant additions of niobium, molybdenum, titanium, and aluminum. These elements precipitate hardening gamma double-prime phases during heat treatment, granting Inconel 718 incredible tensile and yield strength up to around 700 degrees Celsius. However, despite its widespread adoption in turbine disks, fasteners, and rocket components, Inconel 718 falls short in the extreme operating environment of the Raptor engine.

The primary vulnerability of traditional polycrystal alloys like Inconel 718 in the Raptor's combustion environment lies in their grain boundaries and oxidation behavior under ultra-high pressures. At pressures exceeding 800 bar in an oxygen-rich preburner, grain boundaries act as pathways for rapid oxygen diffusion and intergranular oxidation. Furthermore, the high temperatures and pressures create an environment thousands of times more severe than standard atmospheric conditions, causing conventional alloys to suffer from catastrophic metal burning, flaring, and ignition. While Inconel 718 excels in standard aerospace applications, its polycrystalline nature and chemical limitations under extreme oxygen partial pressures necessitated the creation of SX500, a specialized monocrystalline superalloy designed to eliminate grain boundaries entirely and survive where traditional materials fail.

By bypassing the mechanical and oxidative limits of classic Inconel formulations, SX500 establishes a new benchmark for high-pressure, oxygen-rich aerospace metallurgy.

Exploring the elemental makeup and crystalline mechanics of SX500 reveals why traditional alloys fall short, paving the way for advanced manufacturing methods like directional solidification and 3D printing.

Shaping SX500 into high-performance rocket engine hardware requires pushing the boundaries of modern manufacturing science.

Forming a material designed to withstand extreme thermal and mechanical stresses presents a profound paradox in aerospace metallurgy: how to fabricate complex geometries without introducing the internal structural defects that cause high-temperature failure. Conventional machining and standard fabrication methods fall short because they often disrupt the delicate microstructural integrity required for monocrystalline performance. Consequently, manufacturing SX500 demands an absolute mastery over both traditional advanced foundry techniques and cutting-edge digital fabrication processes.

At the core of these manufacturing breakthroughs is the need to carefully control thermal gradients during the primary shaping phases. Because even microscopic flaws, boundary imperfections, or localized residual stresses can propagate rapidly under the extreme operating conditions of a Raptor engine, every production step is optimized to preserve the alloy's unique properties. This has driven aerospace engineers to pioneer specialized methodologies that seamlessly bridge the gap between material science and precision engineering, ensuring that complex parts maintain absolute structural uniformity from the inside out.

As we explore the specific techniques involved, we must look closely at the foundational processes of directional solidification and modern additive manufacturing that make these revolutionary rocket components possible.

Directional solidification serves as the foundational manufacturing technique required to produce the flawless monocrystalline structure that defines SX500 superalloy.

In conventional casting, molten metal cools and solidifies simultaneously from multiple nucleation sites across the mold. This chaotic process creates a patchwork of microscopic crystalline domains, known as grains, which meet at boundaries rich in impurities and defects. Under standard atmospheric and temperature conditions, these grain boundaries are acceptable, but in the extreme thermal and mechanical environment of a SpaceX Raptor engine, they become critical points of structural failure. Grain boundaries act as highways for atomic diffusion, accelerated high-temperature creep, and intergranular oxidation, ultimately leading to catastrophic fracturing when subjected to thousands of pounds of pressure.

To eliminate these inherent vulnerabilities, metallurgists utilize directional solidification to force the crystal growth in a single, strictly controlled orientation. The process begins by pouring the molten SX500 alloy into a specialized ceramic mold resting on a water-cooled chill plate. As heat is precisely extracted downward through the bottom of the mold, a thermal gradient is established. Solidification starts at the chilled base and advances vertically upward at a tightly monitored withdrawal rate. By incorporating a precise geometrical selector or "pigtail" constriction at the base of the mold, only a single, favorably oriented crystal is allowed to propagate upward while all competing grains are choked off.

Controlling the cooling gradient with absolute precision allows the entire casting to grow as one continuous, uninterrupted crystal lattice. Without grain boundaries to impede performance, the SX500 component gains an extraordinary resistance to high-temperature deformation and intergranular cracking. Stress that would normally concentrate at grain boundaries is instead uniformly distributed across the robust monocrystalline matrix. This elimination of internal grain boundaries drastically elevates the creep rupture life and fatigue strength of Raptor engine turbopumps and preburner manifolds, ensuring structural integrity under the most punishing operational pressures in aerospace history.

Through meticulous control of thermal gradients and crystal growth, directional solidification transforms SX500 from a conventional metal framework into a high-performance single-crystal shield capable of withstanding the relentless fury of rocket combustion.

Advanced additive manufacturing transforms how SpaceX processes the SX500 superalloy into critical rocket engine hardware.

Traditional manufacturing methods often fall short when dealing with high-performance nickel-based superalloys designed for extreme thermal and mechanical loads. However, the advent of sophisticated 3D printing, or additive manufacturing, has completely revolutionized the production of Raptor engine hardware. By fusing metal powder layer by layer using high-powered energy sources such as laser or electron beams, SpaceX can fabricate intricate components like turbopumps, manifolds, and preburners with unprecedented precision.

One of the primary advantages of additive manufacturing for SX500 is the ability to create complex internal geometries that conventional subtractive machining simply cannot achieve. Rocket engines require highly optimized internal cooling channels, complex fluid pathways, and integrated manifolds to manage extreme pressures and temperatures efficiently. Through 3D printing, engineers can consolidate multiple parts into a single monolithic structure, drastically reducing potential leak paths, minimizing total weight, and improving overall structural reliability during high-stress flight profiles.

Furthermore, printing components with the SX500 superalloy demands rigorous control over thermal gradients and microstructural development. Because the alloy relies heavily on its unique mechanical properties to withstand extreme operating conditions, the printing parameters must be tightly calibrated to prevent defects like micro-cracking or residual stresses. Post-build thermal treatments are typically employed to homogenize the material and optimize the distribution of strengthening phases, ensuring that the finished additive components match or exceed the performance characteristics required for deep space exploration.

Through innovative additive manufacturing, SpaceX harnesses the full potential of the SX500 superalloy to build lighter, stronger, and more efficient rocket engines.

The integration of these advanced manufacturing methods allows SpaceX to reliably produce intricate, durable hardware that redefines what aerospace materials can achieve.

Ultimately, the SX500 superalloy is much more than just a proprietary material; it is a foundational enabler of the Raptor engine's revolutionary full-flow staged combustion cycle. By overcoming the catastrophic oxidation, extreme high-pressure stress, and thermal creep that inevitably destroy legacy metals like Inconel, SpaceX has redefined what is metallurgically possible in modern aerospace engineering. Through its flawless single-crystal structure and protective passivating oxide layers, SX500 bridges the gap between radical rocket propulsion designs and real-world manufacturing execution. We encourage you to continue exploring our library to learn more about advanced aerospace manufacturing, the intricacies of rocket propulsion cycles, and the cutting edge of additive metallurgy.