Corrosion Resistant Nickel-Cobalt Alloy for Oil and Gas Applications

Applications such as chemical and marine equipment and oil and gas exploration require materials capable of resisting corrosion from seawater, mineral acids and salty environments.

Complex aerospace applications demand materials with higher hardness levels than other alloyed materials.

H.C. Starck Solutions’ MP35N alloy meets all the requirements of such challenging applications.

Overview of MP35N Alloy

MP35N is a nickel-cobalt based alloy from the Multiphase® alloy system. It exhibits a unique combination of properties such as biocompatibility, toughness, corrosion resistance, ductility and ultra high strength.

MP35N can be produced by processes like consumable vacuum arc re- melting and vacuum induction melting. It consists of 10% molybdenum (Mo), 20% chromium (Cr), 35% cobalt (Co) and 35% nickel (Ni).

The alloy possesses good ductility with over 40% reduction in area, and good toughness, as it is strengthened by work hardening and aging at levels of 260ksi to 300ksi. The work hardening can be accomplished by drawing, swaging, rolling or by a combination of these processes.

MP35N can be used at cryogenic temperatures without becoming brittle, and at elevated temperatures up to 600°F (315°C). The ease of fabrication, high modulus, corrosion resistance, high strength and other mechanical properties makes MP35N suitable for high performance applications.

Resistant in Corrosive Environments

The extraordinary corrosion resistance at high strength environments can allow MP35N alloy to resist salt spray, seawater, hydrogen sulfide and mineral acids. The alloy also exhibits improved resistance to hydrogen embrittlement and stress corrosion cracking (SCC).

The use of MP35N in the cold reduced or aged condition is approved by NACE Standard MR-01, “Metallurgy of Oil Field Equipment for Resistance to Sulfide Stress Cracking”, for up to hardness levels of Rockwell C60 for springs and diaphragms. It is one of very few alloys allowed for use as springs at over RC50 hardness levels.

All the four alloying elements present in MP35N, Mo, Cr, Co and Ni, are used to improve corrosion resistance in nickel-based, cobalt-based, and stainless steel industrial alloys, imparting excellent corrosion resistance to MP35N. The chromium content improves the alloy’s resistance against chemical salt reaction, sulfidation and oxidation at high temperatures.

In addition, MP35N exhibits good resistance to stress corrosion cracking, grain boundary attack and pitting as vacuum arc melting produces oxygen, carbon and nitrogen at low levels in addition other residual elements. The nitrogen gas produced is free of undesirable secondary phase.

The overall corrosion resistance in sea water environments is improved by the 1:1 cobalt to nickel ratio and the molybdenum content. In addition, MP35N can function in the presence of hydrogen sulfide. The corrosion resistance properties of MP35N are not based on tensile strength and microstructure. Hence, MP35N can be applied at high strength levels under severe environmental conditions without stress-corrosion cracking.

H.C. Starck Solutions’ MP35N® Alloy Products

MP35N is available as flat rolled plate, sheet, and foil products from H.C. Starck Solutions. They are made up of billets from by Timken Latrobe Steel under license from Standard Pressed Steel Company.

MP35N is suitable for severe spring applications both flat and torsional as it combines high strength and modulus in addition to excellent corrosion resistance. It can be used for diverse applications including medical and surgical spring clips.

The following tables show the available product size, width tolerance and thickness tolerance of flat rolled plate, sheet, and foil products.

Product Thickness inches            mm       Width inches                     mm
Hot Rolled Plate .187–2.00 4.75-50.8 24 max 610
Hot Rolled Sheet .040–.186 1.02-4.74 24 mx 610
Cold Rolled Plate .187–.500 4.75-12.7 24 max 610
Cold Rolled Sheet .005–.186 .127-4.74 24 max 610
Cold Rolled Foil .002–.0049 .0508-.124 12 max 305

Inquire regarding Length

Thickness inches          mm ½-6 in.          12.7-152 mm 6-12 in.          152-305 mm 12-24 in.          305-610 mm
.002 to .010 .0508-0.254 ± .005 ± 0.127 ± .010 ± 0.254 ± .031 ± 0.787
over .010 to .020 0.254-0.508 ± .010 ± 0.254 ± .010 ± 0.254 ± .031 ± 0.787
over .020 to .035 0.508-0.889 ± .015 ± 0.381 ± .015 ± 0.381 ± .031 ± 0.787
over .035 to .060 0.889-1.524 ± .031 ± 0.787 ± .031 ± 0.787 ± .031 ± 0.787
over .060 to .1875 1.524-4.763 ± .062 ± 1.57 ± .062 ± 1.57 ± .031 ± 0.787
over .187 to .500 4.763-12.70 ± .062 ± 1.57 ± .062 ± 1.57 ± .031 ± 0.787

Inquire regarding tolerances for width less than ½ in. / 12.7mm tolerances

Thickness inches         mm Up to 12 in. Wide         305 mm 12 – 24 in. Wide         305-610 mm
.002 to .005 .0508-0.127 ± .0006 ± 0.0152 N/A N/A
over .005 to .008 0.127-0.203 ± .0007 ± 0.0178 ± .0009 ± 0.0229
over .008 to .010 0.203-0.254 ± .0008 ± 0.0203 ± .0010 ± 0.0254
over .010 to .018 0.254-0.457 ± .0010 ± 0.0254 ± .0012 ± 0.0305
over .018 to .035 0.457-0.889 ± .0017 ± 0.0432 ± .0020 ± 0.0508
over .035 to .1875 0.889-4.760 ± 5 % N/A ± 6 % N/A

Mechanical and Physical Properties

The strength of MP35N is primarily enhanced by mechanical working. Tensile and yield strength are affected by processing conditions. Minimum values are achieved in the hot rolled or annealed condition, and are increased in the cold worked condition. Strengths are increased with an aging heat treatment.

The hardness of MP35N increases from approximately Rockwell C7 in the fully annealed condition to Rockwell C50 in the cold worked and aged condition. Typical properties for MP35N are presented in the following tables at various processing conditions. Figure 1 shows the properties of MP35N as-rolled.

Graph illustrating the properties of MP35N as-rolled.

Figure 1. Graph illustrating the properties of MP35N as-rolled.

The following tables present the typical properties of MP35N.

Temperature Thermal Conductivity Electrical Resistivity
°F °C Btu in./hr/ft.2/ °F watt./cm °C µ ohm in µ ohm cm
-300 -184 45 0.065 38.82 99
-100 -73 63 0.091 39.79 101
70 21 78 0.112 40.67 103
200 93 88 0.127 41.37 105
400 204 104 0.150 42.43 108
600 316 118 0.170 43.45 110
800 427 133 0.192 44.44 113
1000 538 148 0.213 45.44 115
1200 649 162 0.234 46.43 118
Temperature Magnetic Susceptibility Magnetic Permeability
°F °C µ emu/g µ
-319 -195 13.47 1.00142
-220 -140 11.07 1.00117
-99 -73 9.81 1.00104
-17 -27 9.22 1.00096
77 25 8.70 1.00092
246 119 8.03 1.00085

Applications

The key applications of flat rolled MP35N products are:

  • High Pulse Magnet Research
  • Aircraft and Aerospace components – Springs, leading edge strips
  • Oil & Gas Industry, Chemical and Marine equipment - high pressure door dogs, springs and valve components
  • Orthodontic and Prosthetic devices

H.C. Starck Fabricated Products

This information has been sourced, reviewed and adapted from materials provided by H.C. Starck Solutions.

For more information on this source, please visit H.C. Starck Solutions.

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