KCl RAP
Grade
RAP = reactive-atmosphere-processed low-absorption single crystal
Grown/purified under HCl reactive atmosphere to strip OH⁻ and metal impurities; pick for high-average-power 10.6 µm CO₂ laser windows.
Values for the RAP condition
Other KCl tempers and conditions
KCl is listed in 3 conditions; see the grade overview at KCl.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SCDefault Single crystal, Bridgman/Czochralski grown, optical grade | Standard optical-grade single crystal for IR windows, prisms and FTIR cells where cost and broad transmission matter more than strength. | — | 2 | 2 | 9 HV | 7 W/m·K |
RAPThis page Reactive-atmosphere-processed low-absorption single crystal | Grown/purified under HCl reactive atmosphere to strip OH⁻ and metal impurities; pick for high-average-power 10.6 µm CO₂ laser windows. | — | 2 | 2 | 9 HV | 7 W/m·K |
Hot-forged / press-forged polycrystalline KCl | Grain-refined by hot forging (~400–600 °C) to raise yield and flexural strength several-fold; used for large high-power CO₂ laser windows that cannot be supported as fragile single crystals. | — | 12 | 3 | 15 HV | 6 W/m·K |
What is KCl RAP?
KCl RAP is KCl in the RAP grade — grown/purified under HCl reactive atmosphere to strip OH⁻ and metal impurities; pick for high-average-power 10.6 µm CO₂ laser windows. KCl RAP has a tensile strength of 2 MPa (0.348 ksi), weaker than 100% of glass grades. Elongation at break is 2% and the elastic modulus is 29.7 GPa (4.31 Msi). KCl RAP has a density of 1.98 g/cm³ (0.0717 lb/in³), lighter than 100% of glass grades. It melts at 771°C (1,420 °F). SC is the default condition FabDigit quotes; RAP is available on request or by drawing note.
Advantages
- Lightweight — 1.98 g/cm³ (0.0717 lb/in³), better than 100% of glass grades
- Easy to machine — 60/100, better than 97% of glass grades
- Ductile — tolerates forming and impact — 2%, better than 84% of glass grades
Limitations
- Needs corrosion protection — 5/100, worse than 98% of glass grades
- Hard to polish — 45/100, worse than 92% of glass grades
- Low stiffness — 29.7 GPa (4.31 Msi), worse than 88% of glass grades
- Low fracture toughness — 0.3 MPa·√m (0.273 ksi·√in), worse than 85% of glass grades
KCl RAP properties
Typical room-temperature values for KCl RAP; 15 are specific to this condition. Other listed values are KCl reference data and may not represent this condition. Bars are the position among glass grades.
Physical5
KCl RAP has a density of 1.98 g/cm³ (0.0717 lb/in³), lighter than 100% of glass grades. It melts at 771°C (1,420 °F).
Mechanical13
KCl RAP has a tensile strength of 2 MPa (0.348 ksi), weaker than 100% of glass grades. Elongation at break is 2% and the elastic modulus is 29.7 GPa (4.31 Msi).
Thermal5
KCl RAP is rated for continuous service to 500°C (932 °F). It conducts heat at 6.5 W/m·K (3.76 BTU/hr·ft·°F), better than 74% of glass grades. Thermal expansion is 36 µm/m·K (20 µin/in·°F).
Electrical3
KCl RAP has an electrical resistivity of 1×10¹¹ Ω·m.
Chemical & Environmental2
Corrosion resistance is not recommended (5/100), worse than 98% of glass grades.
Sustainability3
Producing a kilogram of KCl RAP takes about 40 MJ of energy and emits 3 kg of CO₂ — less than 69% of glass grades. Typical recycled content is 20%.
Manufacturability2
KCl RAP's machinability is good (60/100, better than 97% of glass grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with KCl RAP
Is KCl easy to machine?
Cuts easily with dry diamond saws or single-point diamond turning at light depth of cut; never use water-based coolant — cleave planes {100} make it prone to chipping.
Can KCl be welded?
Not weldable; parts are cemented or mechanically clamped with compliant (indium/PTFE) seats to avoid stress-induced fracture.
Can KCl be formed, bent or molded?
Bulk blanks are Bridgman/Czochralski grown; large windows can be hot press-forged at 400–600 °C to refine grains and raise strength.
What surface finishes work on KCl?
Polish with dry or anhydrous (alcohol/kerosene) slurries in a low-humidity room; AR or moisture-barrier coatings (e.g. ThF₄/ZnSe, parylene) are standard for field use.
KCl chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Kstoichiometric KCl | 52.3 – 52.6 | 52.45 |
| total metallic impuritiesoptical grade, typically ≤20–50 ppm; OH⁻ minimized in RAP material | ≤ 0.01 | 0 |
| Cl | balance | — |
KCl RAP — frequently asked
What is KCl RAP used for?
KCl RAP is typically used for CO2 laser windows, IR spectroscopy optics and IR prisms. In short: low-absorption CO2 laser window; lower cost than KBr; hygroscopic, purge required.
What is the tensile strength of KCl RAP?
KCl RAP has a typical tensile strength of 2 MPa (0.348 ksi) — weaker than 100% of glass grades. Strength varies by condition: see the 3 listed tempers.
Is KCl RAP easy to machine?
Reasonably — machinability is rated good (60/100, better than 97% of glass grades). Cuts easily with dry diamond saws or single-point diamond turning at light depth of cut; never use water-based coolant — cleave planes {100} make it prone to chipping.
Can KCl RAP be welded?
Not weldable; parts are cemented or mechanically clamped with compliant (indium/PTFE) seats to avoid stress-induced fracture.
What surface finishes work on KCl RAP?
Polish with dry or anhydrous (alcohol/kerosene) slurries in a low-humidity room; AR or moisture-barrier coatings (e.g. ThF₄/ZnSe, parylene) are standard for field use.
Can KCl RAP be formed, bent or molded?
Bulk blanks are Bridgman/Czochralski grown; large windows can be hot press-forged at 400–600 °C to refine grains and raise strength.
What is the maximum service temperature of KCl RAP?
KCl RAP is rated for continuous use to about 500°C (932 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Potassium Chloride (KCl) optical material data — Crystran Ltd (2023)
- KCl Kristalle — Kenndaten — Korth Kristalle GmbH (2022)
- Handbook of Optical Constants of Solids — Academic Press (Palik, ed.) (1998)
- Engineered Materials Handbook Vol.4: Ceramics and Glasses — ASM International (1991)
- CRC Handbook of Chemistry and Physics, 102nd ed. — CRC Press (2021)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.