RAYCHIN LIMITED

Precision Center Vent Design

Incoloy vented screws feature a precision-drilled axial bore from the head through the threaded shank. This center vent hole provides an outlet for trapped gases, eliminating virtual leaks and enabling faster pump-down times in high-temperature vacuum systems. The vent diameter is precisely controlled to maintain optimal mechanical strength while providing efficient gas evacuation.

Virtual Leak Elimination

In standard screws, trapped air and gas contaminants in blind-tapped holes create virtual leaks that compromise vacuum quality. The center vent design allows these gases to be pumped away from bottoms, sides, and shoulders, ensuring complete evacuation and maintaining high vacuum integrity at elevated temperatures.

Faster Pump-Down Times

By providing escape routes for trapped gases, Incoloy vented screws significantly reduce the time required to achieve target vacuum levels. This is particularly critical in semiconductor processing, research chambers, and high-temperature vacuum furnaces where productivity depends on rapid cycling.

Pressure Equalization

During thermal cycling in high-temperature vacuum applications, vented screws allow for constant pressure equalization across system components, preventing pressure differentials that could compromise sealing integrity or cause mechanical stress.

Incoloy 800 (UNS N08800 / 1.4876)

High-Temperature General Purpose: Nickel-iron-chromium alloy with excellent oxidation and carburization resistance up to 815°C. Good creep strength and resistance to sigma phase embrittlement. Ideal for vacuum furnace components, heat exchangers, and high-temperature processing equipment. Minimum tensile strength: 585 MPa, yield strength: 240 MPa.

Incoloy 800H (UNS N08810 / 1.4958)

Enhanced High-Temperature Strength: Higher carbon content (0.05-0.10%) provides improved creep and rupture strength. Excellent performance up to 1150°C. Preferred for applications requiring long-term high-temperature stability such as ethylene furnace tubes, steam generators, and high-temperature vacuum furnaces. Maintains structural integrity at extreme temperatures.

Incoloy 800HT (UNS N08811 / 1.4959)

Optimized High-Temperature Performance: Controlled chemistry with aluminum and titanium additions for enhanced creep resistance. Maximum service temperature up to 1150°C. Superior performance in cyclic temperature applications. Ideal for industrial furnace components, radiant tubes, and high-temperature vacuum chamber fasteners.

Incoloy 825 (UNS N08825 / 2.4858)

Acid & Chloride Resistance: Nickel-iron-chromium alloy with molybdenum (2.5-3.5%) and copper (1.5-3%) additions. Exceptional resistance to sulfuric and phosphoric acids. Resists 40% H₂SO₄ at 100°C with <0.05mm/year corrosion rate. Ideal for chemical processing, vacuum systems handling corrosive gases, and marine applications. Maximum service temperature: 540°C in acid service.

Incoloy 925 (UNS N09925)

Sour Service Specialist: Precipitation-hardenable alloy with titanium additions (1.9-2.4%) providing significantly higher strength through aging. Excellent resistance to sulfide stress cracking in H₂S environments. Yield strength 760-965 MPa in aged condition. Ideal for oil & gas downhole tools, sour gas well equipment, and high-strength corrosion-resistant fasteners requiring venting. Qualified per NACE MR0175.

Dimensional Standards

Our Incoloy vented screws meet or exceed the following specifications:

Available in UNC, UNF, UNJF-3A, and metric coarse/fine thread configurations. Vent diameters from 0.5mm to 6mm available.

Material Specifications by Grade

• Incoloy 800: ASTM B408 / ASME SB408, ASTM B163, ASTM B407
• Incoloy 800H: ASTM B408 / ASME SB408, ASTM B163, ASTM B407
• Incoloy 800HT: ASTM B408 / ASME SB408, ASTM B163, ASTM B407
• Incoloy 825: ASTM B424 / ASME SB424, ASTM B423, NACE MR0175
• Incoloy 925: ASTM B805, API 6A, NACE MR0175

Surface Finish Options

• Passivated: Per ASTM A967 for maximum corrosion resistance
• Electropolished: For clean room and pharmaceutical applications
• Ultrasonic Cleaned: For critical vacuum applications
• PTFE Coated: For anti-galling and lubricity
• Silver Plating: Per AMS 2410 for high-temperature anti-seize

Exceptional High-Temperature Strength (800 Series)

Incoloy 800H and 800HT maintain useful strength up to 1150°C. At 900°C, tensile strength remains 130-180 MPa, significantly higher than 316H. Excellent creep rupture strength at 1000°C with 20-25 MPa for 1000 hours.

Superior Acid Resistance (825)

Incoloy 825 vented screws resist 40% H₂SO₄ at 100°C with <0.05mm/year corrosion rate. Excellent performance in phosphoric acid service, including wet process phosphoric acid containing fluoride impurities.

Sour Service Excellence (925)

Incoloy 925 vented screws offer yield strength up to 760 MPa in aged condition with exceptional resistance to sulfide stress cracking. Qualified per NACE MR0175 for H₂S environments up to 425°C.

Virtual Leak Elimination

The precision center vent provides an outlet for trapped gases in blind-tapped holes, eliminating virtual leaks that compromise vacuum quality. Essential for UHV systems operating at elevated temperatures.

Chloride SCC Immunity

With high nickel content (30-46%), Incoloy vented screws have excellent resistance to chloride stress corrosion cracking, making them ideal for marine environments and brackish water applications requiring venting.

Faster Pump-Down Times

By enabling complete evacuation of trapped gases, Incoloy vented screws significantly reduce the time required to achieve target vacuum levels in high-temperature processing equipment.