Nickel Grades 800 / 800H / 825 / DS

1. Introduction to Nickel Alloy Fasteners

Nickel alloy fasteners are specialized engineered fastening components designed for service conditions where conventional stainless steel or alloy steel fasteners may experience corrosion degradation, elevated-temperature strength loss, stress corrosion cracking, or aggressive chemical attack.

Among industrial nickel-based materials, the following grades are extensively utilized:

Grade	UNS Number	Material Family	Typical Application
Incoloy 800	N08800	Nickel-Iron-Chromium Alloy	High-temperature equipment
Incoloy 800H	N08810	Controlled Carbon High Temperature Alloy	Creep-resistant service
Incoloy 825	N08825	Nickel-Iron-Chromium-Molybdenum Alloy	Chemical processing
Nickel DS (Double Strength)	Proprietary/Industry Designation	High Strength Nickel Alloy	Severe industrial duty

These alloys are selected where:

• Elevated temperatures exceed stainless steel capabilities
• Sulfur-bearing atmospheres are present
• Chloride contamination exists
• Acidic chemical exposure occurs
• Long-term creep resistance is required
• Thermal cycling causes differential expansion stresses
• Offshore and petrochemical environments demand superior corrosion resistance

2. Technical Definition of Nickel Alloy Fasteners

Nickel alloy fasteners are threaded mechanical joining elements manufactured from nickel-based alloys containing carefully controlled amounts of:

• Nickel (Ni)
• Chromium (Cr)
• Iron (Fe)
• Molybdenum (Mo)
• Titanium (Ti)
• Aluminum (Al)
• Copper (Cu)

The alloying system creates:

High Temperature Stability

Protective chromium oxide layers remain stable at temperatures where ordinary steels oxidize rapidly.

Corrosion Resistance

Nickel improves resistance to:

• Sulfuric acid
• Phosphoric acid
• Nitric acid
• Chlorides
• Caustic media
• Sour gas environments

Mechanical Integrity

The alloys maintain:

• Tensile strength
• Yield strength
• Ductility
• Fatigue resistance

during prolonged exposure to elevated temperatures.

3. Chemical Composition Overview

Incoloy 800

Element	Typical %
Nickel	30–35
Chromium	19–23
Iron	Balance
Carbon	≤0.10
Aluminum	0.15–0.60
Titanium	0.15–0.60

Incoloy 800H

Element	Typical %
Nickel	30–35
Chromium	19–23
Iron	Balance
Carbon	0.05–0.10
Aluminum + Titanium	Controlled

The higher carbon content promotes superior creep rupture strength.

Incoloy 825

Element	Typical %
Nickel	38–46
Chromium	19.5–23.5
Iron	Balance
Molybdenum	2.5–3.5
Copper	1.5–3.0
Titanium	0.6–1.2

Nickel DS

Element	Range
Nickel	High
Chromium	Moderate
Molybdenum	Variable
Iron	Controlled
Strengthening Elements	Proprietary

Used where enhanced mechanical properties beyond standard nickel alloys are required.

4. Functional Role of Nickel Alloy Fasteners

Fasteners perform a critical structural function:

Primary Functions

• Clamp components together
• Transfer load
• Resist vibration loosening
• Maintain gasket compression
• Preserve structural alignment
• Accommodate thermal expansion

In industrial systems, failure of a single fastener can result in:

• Pressure leakage
• Equipment shutdown
• Production loss
• Safety incidents
• Environmental release

Consequently, material selection is considered a critical engineering decision rather than a procurement-only activity.

5. Fastener Load Mechanics

Understanding load mechanics is essential when specifying Nickel Alloy 800/800H/825/DS fasteners.

The primary loads acting on fasteners include:

Tensile Load

Acts along the bolt axis.

Examples:

• Flanged joints
• Pressure vessels
• Structural connections

Shear Load

Acts perpendicular to bolt axis.

Examples:

• Pipe supports
• Structural frames
• Equipment mounting systems

Combined Loading

Most industrial joints experience both tensile and shear stresses simultaneously.

Cyclic Loading

Repeated load fluctuations generate fatigue stresses.

Examples:

• Compressors
• Pumps
• Turbines
• Rotating machinery

6. Preload Fundamentals

A properly tightened fastener develops preload.

Preload is the intentional tensile force induced in a fastener during tightening.

The preload creates clamping force that holds assembled components together.

Relationship:$$F_{Clamp}=F_{Preload}$$

The objective is:

• Prevent joint separation
• Prevent vibration loosening
• Maintain gasket compression
• Reduce fatigue loading

Insufficient preload causes:

• Leakage
• Joint movement
• Fatigue cracking

Excessive preload causes:

• Thread stripping
• Yielding
• Galling
• Premature failure

7. Preload Calculation Formula

The standard engineering relationship:

$F=0.75\times A_s\times S_y$

Where:

Symbol	Definition
F	Recommended preload
As	Tensile stress area
Sy	Yield strength

Worked Example

M20 Incoloy 825 Bolt

Assumptions:

Parameter	Value
Diameter	20 mm
Stress Area	245 mm²
Yield Strength	220 MPa

Calculation:$$F=0.75\times245\times220$$

$$F=40425N$$

Recommended preload:$$40.4kN$$40.4kN

This preload provides sufficient clamping force while maintaining an adequate safety margin below yielding.

8. Torque-Tension Relationship

Torque applied to a bolt is converted into preload.

However, approximately:

Energy Distribution	Percentage
Thread friction	40%
Bearing friction	50%
Useful preload	10%

Thus:$$T=KFD$$

Where:

Variable	Description
T	Torque
K	Nut factor
F	Preload
D	Nominal diameter

Factors affecting torque:

• Lubrication
• Surface finish
• Coating type
• Thread quality
• Material hardness

Nickel alloys often require controlled lubrication to minimize galling.

9. Force Transfer Mechanisms

Friction-Type Joint

Load transferred by:

• Clamping force
• Surface friction

Common in:

• Structural steel
• Pressure vessel flanges

Advantages:

• Reduced bolt shear
• Improved fatigue life

Bearing-Type Joint

Load transferred through:

• Bolt shank
• Hole contact

Common in:

• Structural assemblies
• Machinery supports

Advantages:

• Higher load capacity

Disadvantages:

• Increased bolt stress

10. Joint Design Principles

Proper joint design ensures fastener reliability.

Key engineering considerations include:

Material Compatibility

Fastener material should match or exceed parent material corrosion resistance.

Examples:

Base Material	Recommended Fastener
Incoloy Equipment	Incoloy 800
Acid Process Equipment	Incoloy 825
High Temperature Furnace	800H
Offshore Nickel Systems	Nickel DS

Joint Stiffness

A stiffer joint experiences:

• Less relaxation
• Better preload retention
• Improved fatigue resistance

Thread Engagement

Minimum thread engagement:

Material	Engagement
Steel	1 × Diameter
Nickel Alloy	1–1.5 × Diameter
Soft Alloy	1.5–2 × Diameter

Thermal Expansion

Nickel alloys exhibit favorable thermal stability.

Typical coefficient:

Material	µm/m°C
Carbon Steel	12
Stainless Steel	17
Incoloy 800	14
Incoloy 825	14.5

This reduces thermal stress mismatch in elevated-temperature assemblies.

11. Fatigue Behavior of Nickel Alloy Fasteners

Fatigue failure accounts for a significant proportion of industrial fastener failures.

The process involves:

1. Crack initiation
2. Crack propagation
3. Final fracture

Fatigue is accelerated by:

• Insufficient preload
• Surface defects
• Corrosion attack
• Stress concentration
• Vibration

Nickel alloys demonstrate superior fatigue resistance compared to many conventional steels due to:

• High ductility
• Stable microstructure
• Corrosion resistance

12. Stress Concentration Effects

Highest stresses occur at:

• First engaged thread
• Thread roots
• Head-to-shank transition
• Under-head fillet

Engineering controls include:

• Rolled threads
• Proper radii
• Controlled machining
• Surface finishing

SM Fasteners employs controlled manufacturing processes to minimize stress raisers and enhance fatigue performance in critical industrial applications.

13. Creep Resistance in Elevated Temperature Service

Creep is time-dependent deformation occurring under sustained load.

Critical for:

• Furnaces
• Reformers
• Boilers
• Heat exchangers
• Thermal reactors

Temperature Threshold

Material	Creep Concern Begins
Carbon Steel	370°C
Stainless Steel	500°C
Incoloy 800	600°C+
Incoloy 800H	650°C+

800H was specifically developed for creep-resistant applications.

14. Elevated Temperature Load Retention

At high temperatures, conventional fasteners lose strength.

Nickel alloy fasteners retain:

• Yield strength
• Tensile strength
• Oxidation resistance

over extended operating periods.

This makes them suitable for:

• Ethylene crackers
• Heat treatment furnaces
• Petrochemical heaters
• Waste heat recovery systems

15. Corrosion-Assisted Load Degradation

Mechanical loads interact with corrosive environments.

Common degradation mechanisms include:

Pitting Corrosion

Localized attack causing stress concentration.

Crevice Corrosion

Occurs beneath gaskets and washers.

Stress Corrosion Cracking

Simultaneous:

• Tensile stress
• Corrosive medium

Hydrogen Damage

Can affect high-strength alloys.

Nickel-based alloys generally provide superior resistance compared with standard stainless steels.

16. Galvanic Considerations

When dissimilar metals contact in conductive environments, galvanic corrosion may occur.

Engineering recommendations:

Component Material	Fastener Recommendation
Nickel Alloy	Nickel Alloy
Duplex Stainless	Duplex/Nickel
Carbon Steel	Isolated Fastener
Aluminum	Insulated Joint

Proper isolation prevents accelerated corrosion.

17. Reliability Engineering Perspective

For EPC projects and critical industrial assets, fastener selection should be based on:

Mechanical Requirements

• Tensile load
• Shear load
• Fatigue load

Environmental Requirements

• Temperature
• Corrosion
• Pressure

Inspection Requirements

• Traceability
• Testing
• Certification

Lifecycle Cost

Lowest purchase cost rarely corresponds to lowest lifecycle cost.

Nickel Alloy 800, 800H, 825, and DS fasteners are frequently selected because reduced maintenance, improved reliability, and extended service life offset higher initial material costs.

18. Engineering Selection Summary

Requirement	800	800H	825	DS
Oxidation Resistance	Excellent	Excellent	Very Good	Excellent
High Temperature	Excellent	Outstanding	Moderate	High
Chemical Resistance	Good	Good	Excellent	Excellent
Sulfuric Acid Service	Moderate	Moderate	Excellent	Excellent
Creep Resistance	High	Very High	Moderate	High
Pressure Equipment	Excellent	Excellent	Excellent	Excellent
Offshore Service	Good	Good	Excellent	Excellent

19. Product Forms Manufactured in Nickel Grades 800 / 800H / 825 / DS

Industrial nickel alloy fasteners are manufactured in a broad range of geometries to accommodate varying load conditions, assembly requirements, maintenance access constraints, pressure-retaining joints, and corrosion environments.

SM Fasteners manufactures precision-engineered fasteners in Nickel Alloy 800, 800H, 825, and DS grades for EPC, OEM, petrochemical, power generation, offshore, and heavy engineering applications.

Standard Product Portfolio

Product Type	Typical Standards
Hex Bolts	ISO 4014, DIN 931
Hex Cap Screws	ISO 4017, DIN 933
Heavy Hex Bolts	ASTM A193
Socket Head Cap Screws	ISO 4762, DIN 912
Stud Bolts	ASTM A193/A320
Threaded Rods	DIN 975, DIN 976
Hex Nuts	ISO 4032, DIN 934
Heavy Hex Nuts	ASTM A194
Lock Nuts	DIN 985
Jam Nuts	DIN 439
Plain Washers	ISO 7089, DIN 125
Heavy Duty Washers	ASTM F436
Spring Washers	DIN 127
Retaining Rings	DIN 471, DIN 472
Custom Fasteners	Project Specific

20. Hex Bolts

Hex bolts remain the most widely used industrial fastening solution.

Characteristics

• Six-sided head
• External wrench engagement
• High torque transmission capability
• Suitable for structural and pressure applications

Typical Applications

• Structural steel assemblies
• Heat exchangers
• Pressure vessels
• Pump skids
• Pipe supports
• Turbine systems

Advantages

• High preload capability
• Easy field maintenance
• Broad dimensional standardization
• Excellent interchangeability

21. Heavy Hex Bolts

Heavy hex bolts feature increased head dimensions compared with standard hex bolts.

Benefits

• Increased wrenching area
• Better load distribution
• Improved high-temperature performance
• Reduced bearing stress

Common in:

• Petrochemical plants
• Refineries
• Offshore platforms
• Boiler systems
• Pressure vessel flanges

22. Stud Bolt

Stud bolts are fully threaded rods used with two nuts.

Advantages

• Uniform load distribution
• Better gasket compression
• Easier maintenance
• Improved flange alignment

Typical Usage

Industry	Application
Oil & Gas	Flanges
LNG	Cryogenic piping
Petrochemical	Pressure vessels
Power Plants	Steam systems
Offshore	Process piping

23. Threaded Rods

Threaded rods provide continuous thread engagement over the full length.

Typical Functions

• Structural anchoring
• Pipe supports
• Equipment mounting
• Hanger systems

Advantages

• Adjustable positioning
• Long-span fastening
• High flexibility

Available in:

• Metric thread
• UNC
• UNF
• Custom threads

24. Socket head cap screws

Socket head screws provide high-strength fastening where access space is limited.

Features

• Internal hex drive
• Cylindrical head
• Precision alignment capability

Applications

• Turbomachinery
• OEM equipment
• Instrumentation systems
• Compact assemblies

25. Nickel Alloy Nuts

Nuts provide thread engagement and preload retention.

Common Types

Nut Type	Function
Hex Nut	General fastening
Heavy Hex Nut	High load applications
Lock Nut	Vibration resistance
Jam Nut	Secondary locking
Slotted Nut	Mechanical locking
Coupling Nut	Rod joining

Nickel alloy nuts are commonly paired with matching alloy bolts to eliminate galvanic compatibility concerns.

26. Industrial Washers

Washers perform several engineering functions.

Functions

• Load distribution
• Surface protection
• Reduction of embedding
• Improved preload retention

Types

Washer Type	Purpose
Plain Washer	General load distribution
Heavy Washer	Structural loads
Spring Washer	Vibration resistance
Belleville Washer	Thermal compensation
Spherical Washer	Misalignment correction

27. Retaining Rings & Specialty Components

Nickel alloy retaining rings are utilized where corrosion resistance and elevated-temperature capability are required.

Applications include:

• Turbines
• Compressors
• Valves
• Rotating equipment

SM Fasteners also manufactures:

• U-bolts
• Eye bolts
• Foundation bolts
• Anchor bolts
• Special forgings
• CNC-machined fasteners
• PEEK fastener assemblies for electrically isolated systems

28. Fastener Geometry Fundamentals

Fastener geometry directly influences:

• Strength
• Fatigue resistance
• Torque transmission
• Preload retention

Critical dimensions include:

Parameter	Description
d	Nominal Diameter
P	Thread Pitch
k	Head Height
s	Width Across Flats
e	Width Across Corners
b	Thread Length
L	Overall Length

29. Metric Thread Geometry

Metric threads follow ISO standards.

Designation:

Example:

M20 × 2.5 × 100

Where:

Element	Meaning
M	Metric thread
20	Nominal diameter
2.5	Pitch
100	Length

30. Standard Metric Thread Pitch Table

Size	Coarse Pitch (mm)	Fine Pitch (mm)
M6	1.0	0.75
M8	1.25	1.0
M10	1.5	1.25
M12	1.75	1.5
M16	2.0	1.5
M20	2.5	1.5
M24	3.0	2.0
M30	3.5	2.0
M36	4.0	3.0
M42	4.5	3.0
M48	5.0	3.0

31. Unified Thread Systems (UNC/UNF)

Used extensively in:

• ASME equipment
• Oil & Gas projects
• North American standards

UNC

Unified National Coarse

Advantages:

• Rapid assembly
• Better contamination tolerance

UNF

Unified National Fine

Advantages:

• Higher preload capability
• Improved vibration resistance

32. UNC Thread Table

Diameter	UNC TPI
1/4″	20
5/16″	18
3/8″	16
1/2″	13
5/8″	11
3/4″	10
7/8″	9
1″	8

Diameter	UNF TPI
1/4″	28
5/16″	24
3/8″	24
1/2″	20
5/8″	18
3/4″	16
7/8″	14
1″	12

34. British Thread Standards

British thread systems remain common in legacy infrastructure and maintenance projects.

BSW

British Standard Whitworth

55° thread angle

BSF

British Standard Fine

55° thread angle

Used in:

• Railways
• Marine systems
• Legacy industrial assets

35. Thread Standards & Tolerance Table

Mandatory Engineering Table

Thread System	Standard	Thread Angle	Typical Tolerance
Metric Coarse	ISO 261	60°	6g / 6H
Metric Fine	ISO 261	60°	6g / 6H
UNC	ASME B1.1	60°	2A / 2B
UNF	ASME B1.1	60°	2A / 2B
BSW	BS 84	55°	Medium
BSF	BS 84	55°	Medium
NPT	ASME B1.20.1	60°	Pipe Taper
BSPT	ISO 7	55°	Pipe Taper

36. Dimensional Logic for Hex Bolts

Hex bolt dimensions are governed by standard proportions to ensure interchangeability.

Example Dimensions

Size	Across Flats s (mm)	Head Height k (mm)
M8	13	5.3
M10	16	6.4
M12	18	7.5
M16	24	10
M20	30	12.5
M24	36	15
M30	46	18.7
M36	55	22.5

37. Dimensional Specification Table

Mandatory Engineering Table

Size	Pitch	Head Width	Head Height	Length Range
M6	1.0	10 mm	4 mm	10–150 mm
M8	1.25	13 mm	5.3 mm	12–200 mm
M10	1.5	16 mm	6.4 mm	16–300 mm
M12	1.75	18 mm	7.5 mm	20–300 mm
M16	2.0	24 mm	10 mm	25–400 mm
M20	2.5	30 mm	12.5 mm	30–500 mm
M24	3.0	36 mm	15 mm	40–500 mm
M30	3.5	46 mm	18.7 mm	50–600 mm
M36	4.0	55 mm	22.5 mm	60–800 mm

38. Thread Engagement Design Rules

Recommended minimum engagement:

Material Combination	Engagement
Steel to Steel	1D
Nickel to Nickel	1.25D
Nickel to Stainless	1.25D
Nickel to Aluminum	2D
Nickel to Cast Iron	1.5D

D = nominal diameter

39. Pressure Vessel Fastening Requirements

Pressure-retaining equipment often requires:

• Heavy hex bolts
• Heavy hex nuts
• Full material traceability
• Certified heat numbers

Applicable standards:

• ASME BPVC
• ASTM A193
• ASTM A194
• ASME PCC-1

Nickel Alloy 800H and 825 are frequently specified for these environments.

40. International Standards Applicable to Nickel Alloy Fasteners

ISO Standards

Standard	Description
ISO 898	Mechanical properties
ISO 4014	Hex bolts
ISO 4017	Hex screws
ISO 4032	Hex nuts
ISO 7089	Plain washers
ISO 965	Thread tolerances
ISO 3506	Corrosion-resistant fasteners

DIN Standards

Standard	Description
DIN 931	Hex bolt partial thread
DIN 933	Fully threaded hex bolt
DIN 934	Hex nut
DIN 125	Plain washer
DIN 127	Spring washer
DIN 912	Socket head cap screw
DIN 975	Threaded rod
DIN 976	Stud bolts

ASTM Standards

Standard	Application
ASTM A193	Alloy bolting materials
ASTM A194	High-temperature nuts
ASTM F436	Hardened washers
ASTM B408	Nickel alloy bars
ASTM B425	Nickel alloy rods
ASTM B564	Nickel alloy forgings
ASTM E8	Tensile testing
ASTM E18	Hardness testing

British Standards

Standard	Application
BS 3692	Fastener dimensions
BS 4190	Hex bolts
BS 1083	Stud bolts
BS 4320	Washers
BS 84	Whitworth threads

41. Interchangeability Considerations

Global EPC projects often require dimensional interchangeability.

Key factors include:

Must Match

• Diameter
• Pitch
• Thread form
• Strength level
• Material grade

Verify Before Replacement

• Head dimensions
• Nut height
• Coating thickness
• Operating temperature
• Corrosion environment

Failure to verify interchangeability can result in:

• Incorrect preload
• Leakage
• Galling
• Fatigue failure

42. Fastener Selection Matrix

Service Condition	Recommended Grade
Furnace Equipment	800H
Steam Reformer	800H
Heat Exchanger	800
Sulfuric Acid Plant	825
Phosphoric Acid Plant	825
Offshore Systems	825 / DS
Chemical Processing	825
Pressure Vessel	800H
LNG Process Equipment	825
Heavy Industrial Duty	DS

43. Engineering Design Summary

Selection of Nickel Alloy 800, 800H, 825, and DS fasteners must consider:

• Load path
• Joint geometry
• Thread engagement
• Thermal expansion
• Corrosion environment
• Applicable international standards
• Inspection and certification requirements

Dimensional compliance with ISO, ASTM, DIN, and BS standards ensures interchangeability, maintainability, and procurement consistency across global industrial projects.

44. Material Selection Philosophy for Industrial Fasteners

Material selection is one of the most critical engineering decisions in fastener design. The selected alloy must satisfy mechanical loading requirements while simultaneously resisting corrosion, thermal degradation, creep, oxidation, and environmental cracking mechanisms throughout the intended service life.

For EPC projects, pressure-retaining equipment, and critical infrastructure, fastener material selection should consider:

Mechanical Requirements

• Tensile strength
• Yield strength
• Fatigue resistance
• Impact resistance
• Creep resistance

Environmental Requirements

• Atmospheric exposure
• Chloride contamination
• Acid service
• H₂S exposure
• Offshore environments
• Elevated temperature operation

Regulatory Requirements

• ASTM compliance
• ASME compliance
• NACE MR0175
• ISO 15156
• Client project specifications

45. Nickel Alloy 800 (UNS N08800)

Material Overview

Incoloy 800 is a nickel-iron-chromium alloy developed for high-temperature oxidation and carburization resistance.

Key Characteristics

• Excellent oxidation resistance
• Stable microstructure
• Good strength retention
• Resistance to thermal cycling
• Resistance to carburizing atmospheres

Typical Service Temperature

Condition	Temperature
Continuous Service	Up to 870°C
Intermittent Service	Up to 980°C

Common Applications

• Heat exchangers
• Industrial furnaces
• Petrochemical heaters
• Boiler components
• Steam systems

46. Nickel Alloy 800H (UNS N08810)

Material Overview

Incoloy 800H is a modified version of Alloy 800 with controlled carbon content and grain size.

Advantages Over 800

• Improved creep resistance
• Superior stress rupture strength
• Better high-temperature stability

Recommended For

• Steam reformers
• Ethylene cracking units
• Furnace construction
• High-temperature reactors

Typical Temperature Capability

Service	Temperature
Continuous	900°C
Peak Exposure	1100°C

47. Nickel Alloy 825 (UNS N08825)

Material Overview

Alloy 825 incorporates molybdenum, copper, and titanium additions to improve corrosion resistance.

Primary Benefits

• Sulfuric acid resistance
• Phosphoric acid resistance
• Chloride SCC resistance
• Pitting resistance
• Crevice corrosion resistance

Typical Applications

• Chemical plants
• Offshore platforms
• LNG facilities
• Desalination systems
• Pollution control equipment

48. Nickel DS Alloy

Nickel DS (Double Strength) fasteners are generally specified where enhanced mechanical performance is required beyond conventional nickel alloy bolting.

Typical requirements include:

• Higher preload capability
• Improved fatigue resistance
• Severe service operation
• High-pressure systems
• Critical rotating equipment

Exact composition and mechanical properties may vary according to project specifications and manufacturing requirements.

49. Material Selection Matrix

Mandatory Engineering Table

Selection Criteria	800	800H	825	DS
High Temperature	Excellent	Outstanding	Good	Very Good
Sulfuric Acid	Fair	Fair	Excellent	Excellent
Phosphoric Acid	Good	Good	Excellent	Excellent
Seawater	Moderate	Moderate	Excellent	Excellent
Chloride SCC Resistance	Good	Good	Excellent	Excellent
Creep Resistance	High	Very High	Moderate	High
Pressure Equipment	Excellent	Excellent	Excellent	Excellent
Offshore Service	Moderate	Moderate	Excellent	Excellent
Cost Level	Medium	Medium-High	High	High

50. Mechanical Properties Comparison

Mandatory Engineering Table

Property	Alloy 800	Alloy 800H	Alloy 825	DS Alloy*
Tensile Strength (MPa)	500–750	450–700	550–770	700–1000
Yield Strength (MPa)	170–310	180–320	220–450	450–750
Elongation (%)	30–45	30–45	30–45	20–35
Hardness (HB)	135–220	135–220	150–220	220–350
Modulus (GPa)	196	196	205	205

*Project-dependent.

51. Material Comparison Table

Mandatory Engineering Table

Material	UTS (MPa)	Yield (MPa)	Corrosion Resistance	Relative Cost	Typical Application
Carbon Steel	400–800	250–640	Low	Low	Structural
SS 304	515–700	205	Good	Medium	General Industrial
SS 316	515–700	205	Very Good	Medium	Marine
Duplex 2205	620–880	450	Excellent	High	Offshore
Alloy 800	500–750	170–310	Excellent	High	Furnaces
Alloy 800H	450–700	180–320	Excellent	High	Reformers
Alloy 825	550–770	220–450	Outstanding	Very High	Chemical Plants
Nickel DS	700–1000	450–750	Outstanding	Very High	Severe Service

52. Corrosion Resistance by Environment

Mandatory Engineering Table

Environment	800	800H	825	DS
Atmospheric	Excellent	Excellent	Excellent	Excellent
Seawater Splash	Good	Good	Excellent	Excellent
Immersion Seawater	Moderate	Moderate	Excellent	Excellent
Sulfuric Acid	Moderate	Moderate	Excellent	Excellent
Nitric Acid	Good	Good	Very Good	Excellent
Phosphoric Acid	Good	Good	Excellent	Excellent
H₂S Service	Good	Good	Excellent	Excellent
Chlorides	Good	Good	Excellent	Excellent
Caustic Service	Good	Good	Very Good	Excellent

53. NACE MR0175 / ISO 15156 Considerations

Oil and gas facilities frequently require compliance with:

• NACE MR0175
• ISO 15156

These standards govern material selection for:

• Sour gas systems
• H₂S environments
• Production facilities
• Refining operations

Critical concerns include:

Sulfide Stress Cracking (SSC)

Hydrogen-induced cracking resulting from H₂S exposure.

Stress Corrosion Cracking (SCC)

Combined mechanical and environmental degradation.

Hydrogen Embrittlement

Particularly important for high-strength fasteners.

Nickel Alloy 825 is widely accepted for sour service applications due to its excellent resistance to these mechanisms.

54. Elevated Temperature Material Selection

Temperature Range	Recommended Material
Up to 400°C	Stainless Steel
400–650°C	Alloy 800
650–900°C	Alloy 800H
Corrosive High Temp	Alloy 825
Severe Service	DS Alloy

55. Heat Treatment Objectives

Heat treatment modifies:

• Strength
• Hardness
• Ductility
• Grain structure
• Residual stress

The goal is to achieve the required balance between mechanical properties and corrosion performance.

56. Solution Annealing

Solution annealing is the most common treatment for nickel alloys.

Process

1. Heating
2. Holding
3. Rapid cooling

Benefits

• Homogeneous microstructure
• Stress relief
• Improved corrosion resistance
• Enhanced ductility

57. Heat Treatment Temperature Ranges

Alloy	Annealing Temperature
800	980–1150°C
800H	1050–1150°C
825	940–980°C
DS	As specified

58. Stress Relieving

Stress relieving reduces residual manufacturing stresses without significantly affecting strength.

Typical applications:

• Large diameter studs
• Precision machined components
• Pressure-retaining bolting

59. Heat Treatment Verification

Verification typically includes:

• Furnace calibration
• Time-temperature records
• Hardness testing
• Metallographic examination

Traceable records are often required for EPC and refinery projects.

60. Manufacturing Workflow Overview

SM Fasteners follows a controlled manufacturing sequence to ensure dimensional accuracy, mechanical performance, and traceability.

Manufacturing Flow

Raw Material Verification → Cutting → Forging → Heat Treatment → Machining → Threading → Inspection → Surface Treatment → Final Testing → Packaging

61. Raw Material Verification

Before production begins, incoming material is verified against:

Documentation

• Mill Test Certificates
• Heat Numbers
• Chemical Analysis Reports

Testing

• PMI verification
• Dimensional checks
• Visual inspection

62. Positive Material Identification (PMI)

PMI confirms alloy chemistry.

Typical methods:

Method	Use
XRF	Rapid verification
OES	Laboratory confirmation

PMI is frequently mandatory for:

• Oil & Gas
• Petrochemical
• Offshore
• LNG projects

63. Hot Forging Process

Forging improves grain flow and mechanical integrity.

Advantages

• Higher strength
• Better fatigue resistance
• Reduced internal defects
• Improved reliability

Suitable for:

• Hex bolts
• Heavy hex bolts
• Studs
• Custom fasteners

64. Machining Operations

Precision machining ensures compliance with dimensional requirements.

Operations include:

• Turning
• Milling
• Drilling
• Slotting
• CNC finishing

Used extensively for:

• Custom fasteners
• Non-standard geometries
• Critical tolerances

65. Thread Manufacturing Methods

Thread Rolling

Material is displaced rather than removed.

Advantages

• Increased fatigue strength
• Compressive residual stress
• Improved surface finish

Thread Cutting

Material is removed by machining.

Advantages

• Large diameters
• Specialty threads
• Low-volume production

66. Thread Rolling vs Thread Cutting

Mandatory Engineering Table

Characteristic	Rolled Thread	Cut Thread
Fatigue Resistance	Excellent	Good
Surface Finish	Superior	Moderate
Production Speed	High	Moderate
Tooling Cost	High	Lower
Large Diameter Capability	Limited	Excellent
Grain Flow	Preserved	Interrupted
Strength	Higher	Lower

67. Surface Finish Requirements

Surface finish influences:

• Corrosion resistance
• Friction coefficient
• Torque behavior
• Galling resistance

Typical roughness:

Surface	Ra Value
Precision Machined	0.8–3.2 µm
Rolled Thread	0.4–1.6 µm
Forged Surface	6.3–12.5 µm

68. Galling Prevention

Nickel alloys may be susceptible to galling under high contact pressures.

Engineering controls:

• Controlled lubrication
• Surface treatment
• Proper torque procedures
• Dissimilar hardness pairing

69. Surface Engineering Options

Nickel alloy fasteners may be supplied with:

• Plain finish
• Passivation
• PTFE coating
• Xylan coating
• Fluoropolymer coating
• Anti-galling lubricants

70. Surface Finish Comparison Table

Mandatory Engineering Table

Finish Type	Corrosion Resistance	Friction Control	Temperature Capability	Typical Use
Plain	Excellent	Moderate	High	General Service
Passivated	Excellent	Moderate	High	Chemical Plants
PTFE	Excellent	Excellent	Moderate	Offshore
Xylan	Excellent	Excellent	High	Oil & Gas
Fluoropolymer	Excellent	Excellent	High	Corrosive Systems
Dry Film Lubricant	Good	Outstanding	Moderate	Anti-Galling

71. Proof Load & Tensile Strength Table

Mandatory Engineering Table

Typical Engineering Values

Size	Stress Area (mm²)	Proof Load (kN)	Tensile Load (kN)
M8	36.6	7.3	18.3
M10	58	11.6	29
M12	84.3	16.9	42.2
M16	157	31.4	78.5
M20	245	49.0	122.5
M24	353	70.6	176.5
M30	561	112.2	280.5
M36	817	163.4	408.5

Actual values vary according to alloy grade, manufacturing condition, and project specifications.

72. Tightening Torque Fundamentals

Torque requirements depend upon:

• Diameter
• Thread pitch
• Lubrication
• Friction coefficient
• Required preload

Nickel alloy fasteners should be tightened using controlled torque procedures to avoid galling and preload inconsistency.

73. Engineering Summary

Nickel Alloy 800, 800H, 825, and DS fasteners provide a unique combination of:

• High-temperature strength
• Corrosion resistance
• Structural reliability
• Fatigue performance
• Long-term service durability

Proper material selection, heat treatment, manufacturing controls, thread production methods, and surface engineering are essential for ensuring performance in critical industrial applications.