Cobalt Alloys

Against abrasive and sliding surfaces, cobalt alloys provide extreme wear resistance. With excellent strength, even in high temperatures, these materials withstand tough, thermal environments.  

Designed for corrosive settings, cobalt alloys are commonly used in the marine, petrochemical and aerospace industries across a variety of applications, including fasteners and bearings. As a biocompatible material, these alloys are periodically in medical prosthetics as artificial joints, hips and knees, as well as dental implants.

At United Titanium, we stock two types of cobalt-based multiphase alloys: UT35N and UT98T. While both yield high strength, UT35N attains an impressive tensile strength of more than 300 ksi. A superalloy, UT98T adheres to the critical requirements necessary for naval marine fasteners.

Contact us for more information. We’ll help you determine the best material for your application.




  • UT35N

    UT35N is a vacuum induction, vacuum arc remelted cobalt-based alloy that offers an unusually favorable combination of high strength and corrosion resistance. The nominal composition of this alloy is 35% Co, 35% Ni, 20% Cr, and 10% Mo.

    In the annealed condition UT35N has a tensile and yield strengths of 135 ksi and 60 ksi, respectively. However, when properly work strengthened and age hardened, this alloy can attain an ultimate tensile strength ofover 300 ksi.

    It is critical to recognize that the strength-imparting hexagonal-close-packed phase can only be achieved through deformation. Therefore, age-hardening of annealed material will not yield these high strengths. The proper combination of cold-work and aging of UT35N produces strength levels consistent with that of the high-strength, low-alloy steels but offers superb ductility, toughness and corrosion resistance as well. These attractive characteristics make alloy UT35N a terrific candidate for high performance fasteners, high strength wire, medical prostheses and marine and aerospace components.

    Due to the difficulty of machining in the age-hardened condition, the manufacture of components in UT35N most often uses AMS 5844 material (solution treated and work strengthened). Once machining and forming operations are complete, the component is age hardened to achieve AMS 5845 properties.

  • UT98T

    Conventional UT159 is an alloy with a unique combination of ultra-high strength, ductility and corrosion resistance capable of 260 ksi or more. It is from this alloy that the new superalloy UT98T (also known as UT159 Modified) evolved for meeting the ever-changing requirements for critical naval marine fasteners.

    UT98T meets the demand for a fastener material with superior fracture toughness to go with high strength and good ductility. While the chemistry of UT98T is identical to that of UT159, superior fracture toughness was achieved while retaining exceptional strength by modifying the cold work and age hardening parameters.

    A key component of the success of this alloy comes from transforming a part of the matrix from one crystal structure to another, thus creating a multiple-phase structure. For this reason UT98T is a terrific candidate for the production of large diameter fasteners since the cold-work and age hardening parameters allow for consistent properties throughout the cross-section of the fastener.


UT35N Mechanical Properties

Common Name UTS (ksi) YS (ksi) EI (%) Ra (%)
  min. min. min. min.
UT35N 260 230 8 35
UT159 265  255  35 
UT98T  200  160  15  40 

UT35N Material Specifications

AMS 5844 Solution Treated and Cold Drawn Rod (Bar) AMS 5845 Solution Treated, Cold Drawn, and Age Hardened Rod (Bar)

UT98T Material Specifications

AMS 5919 Solution Treated and Work Strengthened Bar AMS5920 Solution Treated, Work-Strengthened, and Age Hardened Bar