Best IN738 powder for 3D printing in 2023

Inconel 738 powder is a remarkable superalloy that boasts exceptional strength, heat resistance, and corrosion resistance. With its unique composition and outstanding mechanical properties, this alloy finds applications in diverse industries, including aerospace, power generation, and industrial manufacturing. In this comprehensive guide, we will explore the characteristics, manufacturing process, and wide-ranging applications of Inconel 738 powder.


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Table of Contents

Overview of IN738 Powder for 3D Printing

IN738 is a nickel-based superalloy powder that is widely used for additive manufacturing of high-performance metal parts. It combines excellent mechanical properties at high temperatures with processability, making it an ideal choice for 3D printingaerospace and industrial components.

This article provides a comprehensive guide to IN738 alloy powder for 3D printing applications. It covers composition, properties, print parameters, applications, specifications, suppliers, handling, inspection, comparisons, pros and cons, and frequently asked questions about IN738 powder. Key information is presented in easy-to-reference tables.

Composition of IN738 Powder

IN738 has a precipitation hardening alloy composition containing various solute elements:

Element Weight % Purpose
Nickel Balance Matrix element provides corrosion resistance
Chromium 15 – 17 Oxidation resistance
Aluminum 3.4 – 4.4 Precipitation hardening
Titanium 3.2 – 4.2 Precipitation hardening
Iron 12.5 max Solid solution strengthening
Cobalt 8.5 – 10 Solid solution strengthening
Molybdenum 1.5 – 2.5 Creep strengthening
Tantalum 1 – 2 Precipitation hardening
Carbon 0.11 max Carbide former

Trace amounts of boron, zirconium and magnesium are also added for grain structure control.

Properties of IN738 Powder

IN738 exhibits the following key properties:

Property Description
High strength Excellent tensile and creep rupture strength up to 750°C
Thermal stability Strength and hardness maintained up to 700°C
Oxidation resistance Forms protective Cr2O3 oxide scale
Thermal fatigue resistance Resists cracking during thermal cycling
Corrosion resistance High resistance to hot corrosion and oxidation
Processability Readily weldable using matching filler material

The properties make it suitable for hot section aerospace components exposed to extreme stresses.

3D Printing Parameters for IN738 Powder

Optimized print parameters are needed to process IN738 powder:

Parameter Typical value Purpose
Layer thickness 20-50 μm Thinner layers improve resolution
Laser power 180-500 W Melting condition without evaporation
Scan speed 800-1600 mm/s Balances density and build time
Hatch spacing 50-200 μm Density and mechanical properties
Support structure Minimal Ease of removal, surface finish
Inert gas Argon Prevent oxidation during printing

Parameter selection depends on factors like build geometry, mechanical requirements, surface finish needs and orientation.

Applications of 3D Printed IN738 Parts

Additively manufactured IN738 components serve critical applications in:

Industry Components
Aerospace Turbine blades, combustors, exhaust parts
Power generation Hot gas path parts, heat exchangers
Automotive Turbocharger wheels, valves
Chemical processing Pumps, valves, casings

Benefits over cast/wrought IN738 include complex geometries, reduced lead time and buy-to-fly ratio.

Specifications of IN738 Powder for 3D Printing

IN738 powder is commercially available meeting composition and quality specifications:

Parameter Specification
Particle size range 15-45 μm typical
Particle shape Spherical morphology
Apparent density > 4 g/cc
Tap density > 6 g/cc
Hall flow rate > 23 sec for 50 g
Purity >99.9%
Oxygen content <300 ppm

Other size ranges, purities, and tighter tolerances are possible for specific applications.

Suppliers of IN738 Powder

Reputable IN738 powder vendors include:

Supplier Location
Praxair USA
Carpenter Powder Products USA
Sandvik Osprey UK
Erasteel Sweden
LPW Technology UK

Pricing ranges from $90/kg to $220/kg based on quality, size distribution and order quantity.

Handling and Storage of IN738 Powder

As a reactive metal, IN738 powder requires controlled handling:

  • Store sealed containers in a cool, dry inert gas environment
  • Avoid contact with moisture, acids and oxidizing agents
  • Use conductive containers and transfer equipment
  • Ground equipment to dissipate static charges
  • Minimize dust generation and accumulation
  • Local exhaust ventilation recommended
  • Follow safety data sheet precautions

Proper storage and handling prevents property changes or hazards.

Inspection and Testing of IN738 Powder

Quality testing methods for IN738 powder include:

Method Parameters Tested
Sieve analysis Particle size distribution
Laser diffraction Particle size distribution
SEM imaging Particle morphology and microstructure
EDX/XRF Chemistry and composition
XRD Phases present
Pycnometry Density
Hall flow rate Powder flowability

Testing as per applicable ASTM standards ensures batch-to-batch consistency.

Comparing IN738 to Alternative Alloy Powders

IN738 compares to other Ni-based superalloys as:

Alloy Oxidation Resistance Cost Printability Weldability
IN738 Excellent Medium Excellent Good
IN718 Medium Low Fair Excellent
Haynes 282 Excellent Very High Good Limited
Inconel 625 Good Medium Excellent Excellent

For printability and performance, IN738 provides the best balance compared to alternatives like IN718 or Haynes 282.

Pros and Cons of IN738 Powder

Pros Cons
Excellent strength and oxidation resistance at high temperatures More expensive than IN718 alloy powder
Readily weldable using matching filler Lower room temperature tensile ductility
Widely validated for AM processes Requires hot isostatic pressing to relieve stresses
Performance comparable/superior to cast IN738 Controlled atmosphere storage and handling needed
Complex geometries possible Limited high temperature creep strength

IN738 enables outstanding performance for critical hot section parts but is costlier than other Ni-superalloy options.

Frequently Asked Questions about IN738 Powder for 3D Printing

Here are some common FAQs about IN738 powder:

Q: What particle size is recommended for printing IN738?

A: 15-45 microns is the typical size range used, providing good flowability along with high resolution and density. Finer particles below 10 microns can improve density and surface finish.

Q: What makes IN738 suitable for 3D printing?

A: Key factors are its printability, mechanical properties, weldability, and prior usage in conventional processes that aid validation. IN738 was designed for wrought processing, making it readily adaptable to additive manufacturing.

Q: What post processing is required for IN738 printed parts?

A: Post processes like hot isostatic pressing, heat treatment, and machining are usually needed to relieve stresses and achieve the required dimensions, surface finish, and final properties.

Q: Are support structures necessary for printing IN738?

A: Minimal support structures are recommended to avoid difficult removal from complex surfaces and channels. The spherical IN738 powder flows well and does not require extensive supports.

Q: What are the alternatives to IN738 powder for 3D printing?

A: Key alternatives are IN718, IN625, Hastelloy X, Haynes 282, Mar-M247, and C263. However, IN738 provides the best all-round properties for performance and manufacturability.

Q: What density is achievable with 3D printed IN738 components?

A: Densities over 99% are readily achieved for IN738 with optimized 3D printing parameters. This matches the properties of traditionally processed wrought or cast IN738 products.

Q: Can IN738 parts be machined after 3D printing?

A: Yes, machining processes like turning, drilling and milling can be used for better surface finish and accuracy. Suitable tooling parameters are required for machining precipitation hardened IN738 material.

Q: What is the typical surface roughness of as-printed IN738 parts?

A: Surface roughness (Ra) values of around 8-16 microns are typical but can be further improved using machining and other finishing processes.

Q: Does IN738 require hot isostatic pressing (HIP) after 3D printing?

A: HIP helps relieve internal stresses and achieve 100% density but is not mandatory. For non-critical applications, post-process heat treatment may suffice.

Q: What are common 3D printing defects observed with IN738?

A: Defects like porosity, cracking, distortion, incomplete fusion and surface roughness can occur but are mitigated by optimized parameters and procedures.

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