MP159 Alloy Bar（NACE MR0175 / ISO 15156)

 

 

MP159 (UNS R30159, GH159) is a cobalt-nickel-chromium-based multiphase-strengthened alloy that achieves extremely high strength through cold-drawing-induced ε-phase formation combined with age-precipitation strengthening, while simultaneously possessing excellent corrosion resistance.

 

Typical applications in corrosive environments include:

Oil & Gas: Downhole tool springs, valve components for acidic environments, H₂S-resistant fasteners (NACE MR0175 compliant)

Marine Engineering: Deep-sea connectors, seawater pump shafts, offshore platform fasteners

Chemical Industry: Valves for acidic media, pump springs, instrumentation tubing for highly corrosive environments

Medical Devices: High-strength implants (ISO 5832-6 compliant)

 

Email: susan@lorkgroup.com
WhatsApp: +86 19937075488

 

Regarding the question:susan@lorkgroup.com "Should surface treatment be applied?" Based on our experience, the answer is: "It depends on the specific operating conditions. MP159 inherently possesses excellent corrosion resistance and can be used directly in most marine and acidic environments. However, if the application involves high-pressure acidic fluids (H₂S), applying a coating would actually increase the risk of hydrogen embrittlement, which is why many oilfield service clients opt against using coatings."

We have compiled a list of key questions frequently raised by customers inquiring about MP159 alloy purchases, as well as the critical technical parameters we need to discuss before issuing a formal quotation, to help us quickly finalize the specific details of your quote:

• Specifications: Diameter (typically d5–25 mm cold-drawn bar stock used for fasteners)
• Supply Condition: Cold-drawn (requiring in-house aging treatment) or Aged (ready for immediate use)?
• Hardness Requirements: Standard HRC 45–50, or Oil & Gas Service Grade HRC 49–52?
• NACE Certification: Is compliance with NACE MR0175 required?
• Melting Process: Is a dual-vacuum process (VIM + VAR) required?

Recommendations for Condition Selection:

Customers with heat treatment capabilities → Purchase Cold-drawn material (bar or wire stock) and perform the aging treatment in-house.

Customers requiring immediate use → Purchase Aged material (at a higher cost).

Oil & Gas Service Customers → Verify whether the required hardness falls within the HRC 49–52 range.

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(Cold-drawn 48% + Aged)

High-Temperature Strength Retention: At 600°C, the tensile strength of MP159 alloy remains approximately 1000 MPa. This indicates that it retains sufficient strength even in high-temperature, corrosive environments, such as acidic downhole conditions.

This constitutes the most critical drawback of MP159-and, indeed, an additional hurdle for its application in corrosive environments. Such applications often necessitate surface plating treatments, which in turn introduce the risk of hydrogen embrittlement-an issue that is even more critical in corrosive settings than it is in aerospace applications.

1. Three-Step Process Method

The standard processing sequence for MP159 consists of three indispensable steps: solution annealing, 48% cold drawing deformation, and age hardening. The critical element is the 48% cold drawing deformation; even a slightly lower reduction in area results in a significant drop in strength by a full grade. If you were to purchase the material in its solution-annealed state and perform only the subsequent aging treatment, the resulting strength would be merely 1000 MPa, rendering the purchase essentially a waste of money.

2. Hydrogen Embrittlement-The Foremost Risk in Corrosive Environments

This is the issue requiring the utmost attention in applications involving corrosive environments. Although MP159 inherently possesses superior resistance to hydrogen embrittlement compared to many other high-strength materials, it is imperative to perform a hydrogen removal treatment-specifically, holding the material at 190–220°C for a minimum of 23 hours-if surface treatments involving electroplating (such as cadmium, zinc, or chromium plating) are to be applied.

Note: If your application in a corrosive environment necessitates a protective surface coating, it is essential to perform a hydrogen removal treatment-specifically, baking at 230°C for at least one full day-*prior* to electroplating. Failure to do so carries a high risk of delayed cracking; hydrogen may diffuse into the material over the months following electroplating, eventually leading to failure.

3. Specific Requirements for the Oilfield Services Industry-Higher Hardness

4. Machining-High Hardness After Aging; Requires the Use of Carbide Tools

One-stop Special Steel Factory in China

We stock MP159 bars in various sizes and process them in-house to exact lengths to suit your engineering requirements.

No matter what you need for your application, our team is here to help. We provide world-class customer support for every order, as well as value-added services like cutting, heat treating, grinding, and more. Contact us for a quote today.

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