What is A Vickers Hardness Tester?

The relationship between Vickers hardness tester and pipes

Inconel Pipes

• Application:
  Deepwater subsea oil trees,aerospace fuel lines,and nuclear steam generator tubing.
• Vickers Purpose:
  Monitoring detrimental phase precipitation and age-hardening efficiency.

When welding Inconel 625 pipes,poor interpass temperature control causes an extremely brittle micro-phase known as the Laves phase to form.This elevates local hardness from a normal 200–240 HV to over 350 HV,making the weld highly susceptible to cracking under thermal fatigue.

For precipitation-hardened Inconel 718 tubes,micro-Vickers testing is applied directly across the grain boundaries to verify that post-weld heat treatment successfully achieved the target 360–450 HV range required for high-temperature creep resistance.

Hastelloy Pipes

• Application:
  Chemical processing plants,pesticide manufacturing,and highly concentrated acid pipelines (HCl, H₂SO₄).
• Vickers Purpose:
  Preventing Intergranular Corrosion (IGC) in the Heat-Affected Zone (HAZ).

During the welding of Hastelloy C276 pipes,a microscopic,hard compound called the μ phase can precipitate in the fusion line.

Inspectors execute a high-density Vickers traverse across the weld line.If local hardness spikes from the base metal average of 210 HV up to 280 HV or higher,it indicates heavy elemental segregation.The pipe will suffer rapid localized corrosion and pinhole leaks at that specific “hard point” when exposed to live chemicals.

Super Duplex Pipes

• Application:
  Seawater desalination high-pressure lines,marine piping,and offshore oil platforms.
• Vickers Purpose:
  Strict containment of the brittle σ phase.

Super duplex pipe relies on a precise 50/50 balance of austenite and ferrite.If exposed to incorrect welding temperatures (600°C–1000°C),the ferrite instantly converts into the notoriously brittle σ phase.Even 1% of σ phase destroys corrosion resistance and makes the pipe brittle like glass.

Under NORSOK M-630 / M-601 and ASTM A923 standards,the maximum allowable hardness for a Super Duplex 2507 weld cap or HAZ is strictly capped at 310 HV10 or 320 HV10.A Vickers tester is the most reliable,cost-effective tool to instantly screen for σ phase formation during a Welding Procedure Qualification.

Monel Pipes

• Application:
  Marine splash-zone piping,seawater heat exchangers,and hydrofluoric acid alkylation units.
• Vickers Purpose:
  Measuring cold-work hardening gradients and evaluating stress-relief annealing.

Monel 400 pipe is a solid-solution nickel-copper alloy pipe with a soft baseline hardness of 140–180 HV. However, during pipe bending or cold drawing,it undergoes rapid work hardening,pushing hardness values past 260 HV,which triggers severe Hydrogen Stress Cracking.

Vickers testers are used to map the hardness gradient across the bend radius of Monel 400 elbows,ensuring that post-bend stress-relief heat treatment successfully brings the material back below the dangerous hardness threshold.

Incoloy Pipes

• Application:
  Petrochemical pyrolysis furnace tubes,flare stacks,and downhole Oil Country Tubular Goods in sour wells.
• Vickers Purpose:
  Validating safety margins against sulfide stress cracking.

Incoloy 825 pipes used in high-CO₂ and H₂S oil wells are heavily regulated by NACE MR0175 / ISO 15156.

To prevent catastrophic environmental stress cracking,the weldment hardness is strictly limited to 250 HV max. Because Incoloy OCTG tubing frequently features thin walls,a Rockwell cone would bend or puncture the tube wall, yielding inaccurate data.A Vickers machine applying low force (HV5 or HV10) provides highly accurate hardness readings without distorting the structural shape of the thin-walled pipe.

Pure Nickel Pipes

• Application:
  Sodium hydroxide (caustic soda) evaporators and high-purity chlorine gas transfer lines.
• Vickers Purpose:
  Detecting graphitization embrittlement in ultra-soft metals.

Nickel 200 pipes are exceptionally soft,with an annealed baseline hardness of only 90–110 HV.When exposed to temperatures above 315°C,carbon precipitates along the grain boundaries as graphite,ruining the pipe’s integrity (which requires a switch to low-carbon Nickel 201).

Rockwell scales are entirely useless on material this soft.Brinell balls cause massive,destructive indents.A Vickers tester utilizing an ultra-light HV1 or HV5 load is the only industrial methodology that can precisely measure the micro-hardness of pure nickel pipes to ensure correct annealing without ruining the pipe wall.