Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
21CrMoV5-7 Hardness (EN 10269 / 1.7709)
The hardness of 21CrMoV5-7 (Werkstoff 1.7709) in the quenched-and-tempered condition falls in the range 210 to 250 HBW to EN 10269. The hardness window is set tight enough to confirm the Q+T cycle landed in the correct secondary-hardening temper range. Hardness above 250 HBW indicates under-tempering; below 210 HBW indicates over-tempering.
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Hardness Ranges in Q+T Condition
| Scale | Range | Notes |
|---|---|---|
| Brinell HBW | 210 to 250 | To EN 10269; 10 mm ball / 3000 kgf |
| Vickers HV | 220 to 265 | Conversion to ISO 18265 |
| Rockwell HRC | 20 to 26 | Conversion to ISO 18265 |
Hardness Test Method
Brinell HBW to ISO 6506-1 / ASTM E10 with 10 mm tungsten-carbide ball at 3000 kgf load. Vickers HV to ISO 6507-1 / ASTM E92 with 10 kgf load. Rockwell HRC to ISO 6508-1 / ASTM E18 with 150 kgf major load. Three readings per piece, averaged for the certificate.
Weld and HAZ Hardness
For welded joints, hardness traverse across weld plus HAZ plus parent is performed after PWHT. Maximum acceptable HAZ hardness is 320 HBW (34 HRC) to EN ISO 15614 standard practice. Higher hardness indicates inadequate PWHT or hydrogen embrittlement risk.
Hardness After Surface Treatments
Manganese phosphate to MIL-DTL-16232 (anti-galling pre-treatment): no measurable effect on base hardness. Molybdenum-disulphide dry-film lubricant: no effect. Xylan / xylar fluoropolymer coating: no effect; coating thickness 20 to 30 micrometres does not contribute to surface hardness measurement.
Frequently Asked Questions
Q. What hardness range is 21CrMoV5-7 supplied in?
210 to 250 HBW to EN 10269 in the Q+T condition. Vickers equivalent 220 to 265 HV; Rockwell C equivalent 20 to 26 HRC.
Q. What is the maximum allowable hardness in the weld HAZ?
320 HBW (34 HRC) to EN ISO 15614 standard practice. Higher HAZ hardness indicates inadequate PWHT and risks hydrogen embrittlement or stress-corrosion cracking in service.
Q. Which hardness test method is standard for 21CrMoV5-7?
Brinell HBW to ISO 6506-1 or ASTM E10 with 10 mm tungsten-carbide ball at 3000 kgf load. Three readings per piece, averaged on the certificate. Vickers HV and Rockwell HRC supplied on call-out for projects that specify those scales.
Q. Does hardness change with elevated-temperature service?
Slowly. Long-term exposure at 500 to 550 deg C causes gradual coarsening of V4C3 carbides and a slow hardness drop of 5 to 10 HBW per 100,000 hours. Bolts that drop below 200 HBW indicate over-temper from extended service and should be replaced at the next outage.
Related Properties Pages
Drill into 21CrMoV5-7 properties: Chemical Composition · Mechanical Properties · Heat Treatment · Elevated-Temperature Properties · Creep-Rupture · Welding Procedure · Machinability. Standards: EN 10269 · vs ASTM A193 B16. Back to the 21CrMoV5-7 Alloy Hub.
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