RAYCHIN LIMITED

MP159 Hex Cap Screws – Design & Configurations

Critical Applications of MP159 Hex Cap Screws

International Standards & Global Designations – MP159 Hex Cap Screws

RAYCHIN LIMITED manufactures MP159 hex cap screws from vacuum induction melted (VIM) and vacuum arc remelted (VAR) material conforming to the most widely used national and international specifications . All material is traceable to the mill.

Chemical Composition (Weight %) – MP159 Alloy for Hex Cap Screws

Our MP159 hex cap screws are produced from vacuum induction melted (VIM) and vacuum arc remelted (VAR) material conforming to the following limits per AMS and industry standards .

Metallurgical note: MP159 is a multiphase cobalt-nickel-chromium-molybdenum alloy strengthened through a unique combination of solid solution strengthening, cold work hardening (typically 48% reduction), and age hardening via precipitation of γ' phase [Ni₃(Al, Ti, Nb)] and ε phase formation . The alloy maintains excellent ductility even at high cold reduction levels, enabling production of high-strength hex cap screws with precision-formed heads and rolled threads. It remains essentially non-magnetic (permeability ~1.00265 μ) even after extensive cold working, critical for medical and directional drilling applications . MP159 was developed specifically for higher operating temperatures compared to MP35N, with service capability up to 1100°F (593°C) . Heat treatment per AMS 5843: solution anneal 1900-1925°F (1040-1055°C), 48% cold work, age 1200-1250°F (650-675°C) for 4-4.5 hours . The high chromium (19%) and molybdenum (7%) content promotes formation of a dense Cr₂O₃ protective film, providing exceptional hot corrosion resistance .

Complete Mechanical & Physical Properties – MP159 Hex Cap Screws (MPa / ksi)

MP159 hex cap screws are supplied in various conditions per AMS specifications. Data represent typical values based on AMS and industry standards . ksi values (kilopound per square inch) are provided alongside MPa.

Mechanical Properties by Condition – MP159 Hex Cap Screws

Physical Properties – MP159 Alloy

High‑Temperature Performance of MP159 Hex Cap Screws

MP159 alloy was developed specifically to meet the need for a fastener alloy that could perform under the higher operating temperatures required for turbine engines and other high performance motors . It has advantages similar to MP35N but can perform in applications up to 593°C (1100°F) and is suitable for short term use at even higher temperatures (up to 649°C/1200°F) . The high chromium content (19%) promotes formation of a dense, protective Cr₂O₃ film that provides excellent hot corrosion resistance in aggressive environments .

Elevated Temperature Capabilities

High-Temperature Comparison – MP159 vs. MP35N

Note: MP159 fills the critical gap between MP35N and higher-temperature alloys like Inconel 718, offering superior strength up to 1100°F with excellent corrosion resistance .

Exceptional Corrosion Resistance of MP159 Hex Cap Screws

MP159 alloy offers outstanding corrosion resistance across a wide range of aggressive environments, making it suitable for the most demanding applications including medical implants, downhole tools, marine equipment, and chemical processing .

• General Corrosion Resistance: Similar corrosion resistance to MP35N, excellent resistance to most mineral acids, hydrogen sulfide, seawater and salt spray environments .
• Stress Corrosion Cracking (SCC): Exceptional resistance to chloride and sour (H₂S) environments. Qualified per NACE MR0175 for oil & gas applications .
• Pitting and Crevice Corrosion: Superior resistance to localized corrosion in seawater and brine solutions due to high chromium (19%) and molybdenum (7%) content. Virtually immune to crevice corrosion and pitting even at the highest strength levels .
• Hydrogen Embrittlement: Excellent resistance to hydrogen embrittlement when properly heat treated .
• Hot Corrosion Resistance: Superior hot corrosion resistance at elevated temperatures due to formation of dense Cr₂O₃ protective film, promoted by high Cr content and the presence of Nb .
• Oxidation Resistance: In 900°C air, oxidation rate <0.1 mm/year, superior to many competing alloys .
• Seawater Performance: In seawater, MP159 is virtually immune to crevice corrosion, stress corrosion cracking, and pitting .
• Biocompatibility: Fully biocompatible for medical implant applications .
• Bimetallic Corrosion: Can be safely connected to stainless steels, titanium alloys, and other corrosion-resistant alloys with appropriate precautions.

Manufacturing Standards – MP159 Hex Cap Screws

All MP159 hex cap screws are manufactured and tested to meet the following standards:

We offer surface finishes: passivation (ASTM A967), silver plating (AMS 2410 for anti‑seize), PTFE coating, electropolish. Full traceability and destructive/non‑destructive testing available (UT, MPI, PMI). ISO 13485 certified for medical applications with cleanroom packaging available.