CNC Machining Guides
Titanium Grade 5 vs Grade 23: Which to Choose?
Grade 5 or Grade 23 titanium? Compare strength, ductility, biocompatibility, corrosion, machining and cost—and learn which Ti-6Al-4V grade to specify for CNC parts.
A medical program specified Grade 5 titanium because it was "the standard titanium." The design review came back with a question: does the implant require the extra-low-interstitial Grade 23? The answer changed the material, the certification, and the cost.
Another program specified Grade 23 for an industrial bracket because it was "the better titanium." The part did not need the extra ductility, and the buyer paid a premium for a property the application did not use.
Grade 5 and Grade 23 are both Ti-6Al-4V titanium alloys. They look the same on the drawing and machine in similar ways. The difference is in the chemistry limits, the ductility and fracture toughness, the certification, and the application. The right choice depends on the function, not on the grade number.
This guide is written for design engineers and buyers who need to choose between Grade 5 and Grade 23 titanium for CNC machined parts. It covers the metallurgy, strength, ductility, medical and aerospace applications, corrosion, machining, cost, and the questions to ask before quoting.
The Short Answer
Choose Grade 5 (Ti-6Al-4V) for high-strength industrial, aerospace, and instrument components where the standard interstitial limits are acceptable. Choose Grade 23 (Ti-6Al-4V ELI) when the application needs improved ductility and fracture toughness, or when the material specification requires extra-low interstitial content, such as many medical implants and fracture-critical aerospace parts. Specify the grade, the material specification, the condition, and the certificate. Do not assume that Grade 23 is always better; it is a different balance of properties and cost.
A Quick Way to Decide
If the part is an implant, or must survive damage without cracking, Grade 23 is usually the safer starting point. If the part is a strong industrial or aerospace component and the specification allows standard interstitial limits, Grade 5 is usually enough.
If you are not sure, describe what the part must survive—load, corrosion, cleaning, implant, inspection—and ask the supplier to recommend a grade. Do not choose by the grade number alone.
What Grade 5 and Grade 23 Are
Grade 5 is the workhorse Ti-6Al-4V alloy. It contains 6 percent aluminum and 4 percent vanadium, and it is used for aerospace structures, medical instruments, high-performance automotive parts, and industrial components. It is available in bar, plate, sheet, and forgings, and it is widely stocked.
Grade 23 is the extra-low-interstitial version of Ti-6Al-4V. The oxygen, nitrogen, carbon, and iron limits are tighter. The lower interstitial content improves ductility and fracture toughness. Grade 23 is commonly specified for medical implants and for fracture-critical aerospace components.
The two grades are not interchangeable without a review. The chemistry limits, the mechanical properties, the certification, and the application requirements are different. The drawing should state the grade and the material specification, not just "Ti-6Al-4V."
Strength and Ductility
Grade 5 has high strength and good fatigue resistance. It is the default choice when the application needs high strength at low weight. The exact strength depends on the condition and the product form.
Grade 23 has similar strength but improved ductility and fracture toughness because of the lower interstitial content. It is not necessarily weaker; it is a different balance. The extra ductility can be important in a implant, a fracture-critical component, or a part that must tolerate damage.
The trade-off is not "strong versus weak." It is "strength and cost versus ductility and damage tolerance." The design should define which property matters for the application.
Medical Applications
Grade 23 is common for medical implants because of its biocompatibility, corrosion resistance, and ductility. The material specification often requires the extra-low-interstitial grade, and the certificate and traceability are part of the device file.
Grade 5 is used for medical instruments, trial components, and some non-implant applications. It is stronger and more widely available, but it may not meet the implant specification.
If the part is for a medical device, the material specification, the quality system, and the documentation should be confirmed before the order. Zync Precision holds ISO 9001 and IATF 16949; if the device program requires ISO 13485 or FDA registration, confirm the supplier scope before placing the order.
Aerospace and Industrial Applications
Grade 5 is common in aerospace structures, brackets, fasteners, and engine components. It offers high strength and good fatigue resistance, and it is widely available.
Grade 23 is used for fracture-critical or damage-tolerant components where the improved ductility and toughness are required. It may also be specified when the material specification calls for the ELI chemistry.
For industrial applications, Grade 5 is usually sufficient unless the environment or the specification requires Grade 23. A bracket or a machine component does not automatically need the ELI grade. The buyer should avoid over-specifying.
Interstitial Elements and Why ELI Matters
The "ELI" in Grade 23 means extra-low interstitial. The interstitial elements are oxygen, nitrogen, carbon, and iron. They sit in the crystal lattice and affect the strength, the ductility, and the toughness.
A lower oxygen content generally improves ductility and fracture toughness. It can also reduce the risk of brittle behavior in a fracture-critical part. The limits are specified in the material standard, and the certificate should confirm them.
The difference is not visible on the drawing. Two parts can look identical and have different interstitial content. The material specification and the certificate are the only way to confirm which grade was used.
For a medical implant or a fracture-critical component, the ELI requirement should be stated explicitly. A supplier should not substitute Grade 5 for Grade 23 without the customer's approval.
Medical Implant Specifications
Medical implants often require a specific titanium specification, such as an ASTM or ISO standard for Ti-6Al-4V ELI. The standard defines the chemistry, the mechanical properties, the microstructure, and the test methods.
The material certificate should match the specification and the lot. The traceability should connect the raw material to the finished part. The cleaning, the surface finish, and the packaging are part of the device requirements.
The buyer should confirm the applicable standard with the device team. A generic "medical-grade titanium" is not a specification. The quality system and the supplier scope should also be confirmed before the order.
Aerospace Fracture-Critical Parts
Aerospace fracture-critical parts may require Grade 23 for the improved toughness and damage tolerance. The material specification, the heat treatment, the inspection, and the traceability should be defined by the program.
Grade 5 is common for many aerospace structures and brackets. Grade 23 is used where the fracture mechanics or the customer specification requires it. The choice should be based on the stress, the damage tolerance, and the program requirement, not on a general preference.
If the program requires AS9100 or a specific aerospace quality system, confirm the supplier's certificate and scope before the order. Zync Precision holds ISO 9001 and IATF 16949; the program requirements should be checked separately.
Corrosion and Biocompatibility
Both grades have excellent corrosion resistance and biocompatibility. They form a stable oxide layer and resist many chemicals and body fluids.
The corrosion resistance is not unlimited. Titanium can suffer crevice corrosion in some hot chloride environments, and it can be attacked by some chemicals. The environment and the cleaning chemistry should be reviewed for critical applications.
For medical applications, the biocompatibility and the surface condition matter. The material grade, the surface finish, the cleaning, and the sterilization should be considered together. A certificate alone does not prove biocompatibility; the device evaluation and the quality system are part of the program.
Machining and Heat Treatment
Both grades are machined in similar ways. Titanium has low thermal conductivity, work-hardens, and can gall. Sharp tools, high-pressure coolant, rigid setups, and a process designed for titanium are required.
Grade 23 may behave slightly differently because of the chemistry, but the machining strategy is similar. The main differences are the material certification, the availability, and the cost.
Heat treatment and stress relief should be specified when required. Titanium parts can distort during machining and heat treatment, especially thin or asymmetric parts. The sequence and the final inspection should account for it.
Cost and Availability
Grade 5 is widely available and generally less expensive than Grade 23. It is stocked in many sizes and forms, and the lead time is usually shorter.
Grade 23 is more specialized. The material may be more expensive, the availability may be limited, and the certification requirements may be stricter. The extra cost should be justified by the application.
The total cost includes the material, the machining, the certification, the heat treatment, and the inspection. A Grade 23 part that is not required adds cost without adding value. A Grade 5 part that does not meet the specification can cost more in rework or recall.
Decision Checklist
Ask these questions before choosing.
Does the application require extra ductility or fracture toughness? Does the material specification call for ELI chemistry? Is the part an implant or a fracture-critical component? What is the quality system and the certification requirement? What is the cost and lead time for each grade? Is Grade 23 available in the required form and size? Does the buyer's specification allow Grade 5?
If the answers point to a standard high-strength application, Grade 5 is often the starting point. If they point to ductility, damage tolerance, or a medical implant specification, Grade 23 may be required.
What to Put in the RFQ
State the grade and the material specification. For Grade 5, state the condition and the product form. For Grade 23, state the ELI requirement and the applicable specification.
State the application, the critical features, the tolerance, the surface finish, and the inspection method. If the part is for a medical or aerospace program, state the quality system and the documentation requirement.
State the quantity, the delivery destination, and the certification requirement. If the material must be from a specific mill or heat lot, say so.
Common Buyer Mistakes
The first mistake is choosing by grade number. A higher number does not mean a better material for your part. The application decides.
The second mistake is leaving the material specification off the drawing. "Titanium" or "Ti-6Al-4V" is not enough for a regulated or critical part. The grade, the specification, the condition, and the certificate should be stated.
The third mistake is assuming that Grade 23 is always stronger. Grade 23 is chosen for ductility and toughness, not for a higher strength number. If your part needs strength and the specification allows Grade 5, Grade 23 may add cost without adding value.
The fourth mistake is forgetting the heat treatment or condition. The material properties depend on the condition. A certificate that does not match the condition is a problem waiting to happen.
If you are unsure, ask the supplier to review the drawing and the application before you finalize the material. A good supplier will tell you when a grade is over-specified, not just quote the most expensive option.
FAQ
Is Grade 23 stronger than Grade 5?
Not necessarily. Grade 23 has improved ductility and fracture toughness because of the lower interstitial content. The strength is similar; the balance of properties is different.
Can Grade 5 be used for medical implants?
Some medical applications use Grade 5, but many implant specifications require Grade 23 ELI. The device specification and the quality system should be confirmed before the material is selected.
Why is Grade 23 more expensive?
The ELI chemistry, the certification, and the availability add cost. The material may be more specialized and less stocked than Grade 5.
Is Grade 23 harder to machine?
The machining strategy is similar. The main differences are the certification, the availability, and the cost. Titanium machining requires sharp tools, coolant, and process control for both grades.
Do you machine both grades?
Yes. Zync Precision machines Grade 5 and Grade 23 titanium from customer drawings, with material traceability and dimensional inspection. The material specification and the documentation requirement should be stated in the RFQ.
Choosing a Titanium Machining Supplier
A titanium supplier should ask about the application, the grade, the specification, and the documentation before quoting. The supplier should be able to machine both grades and control the material traceability.
Zync Precision is an ISO 9001 and IATF 16949 certified manufacturer of custom CNC machined parts for medical, aerospace, consumer electronics, and automotive applications. We machine Grade 5 and Grade 23 titanium, with material traceability, dimensional inspection, and production support. Our engineering team reviews drawings, materials, tolerances, surface finishes, and delivery, and responds to quote requests within 24 hours. If you are choosing between Grade 5 and Grade 23, send your drawing, application, material specification, quantity, and destination.
Request a CNC machining quote and let us review your titanium project.