FDA
FDA 21 CFR 1040.10 - Laser Product Performance Standards
Yi-Chun LinPh.D.Taiwan
Laser Materials ProcessingPublished
Dec 16, 2025
Molybdenum Laser Cleaning
Molybdenum exhibits high heat resistance, so laser cleaning removes contaminants effectively without surface damage. During processing, its reflectivity challenges energy absorption, yet strong thermal shock tolerance ensures durability for aerospace parts. Treatment achieves clean uniformity.
Laser-Material Interaction
Absorption Coefficient
4.2e7
m^-1
5.9e5
4.2e7
9.9e7
Absorptivity
0.41
0.02
0.41
0.6
Laser Damage Threshold
0.45
J/cm²
0.27
0.45
1.6e4
Reflectivity
0.57
0.35
0.57
1
Thermal Destruction Point
2,896
K
133
2,896
3,865
Thermal Shock Resistance
515
W/m
6.7
515
3.8e5
Vapor Pressure
1.3e-7
Pa
0
1.3e-7
1.1e5
Thermal Destruction
2,896
K
256
2,896
3,859
Specific Heat
251
J/(kg·K)
43.4
251
1,905
Laser Reflectivity
0.61
fraction
0.4
0.61
73.5
Thermal Conductivity
138
W/m·K
7.4
138
450
Thermal Expansion
4.8e-6
K^{-1}
4e-6
4.8e-6
31.7
Laser Absorption
0.43
0.02
0.43
4.2e8
Thermal Diffusivity
5.4e-5
m²/s
2e-6
5.4e-5
0
Ablation Threshold
2.1
J/cm²
0.09
2.1
4.3
Molybdenum Laser Cleaning Material Characteristics
Electrical Conductivity
1.9e7
S/m
6.6e5
1.9e7
6.6e7
Electrical Resistivity
5.2e-8
Ω·m
0
5.2e-8
2e-6
Fracture Toughness
0.9
MPa m^{1/2}
0.67
0.9
157
Surface Roughness
0.8
μm
0.02
0.8
6.6
Youngs Modulus
329
GPa
10.4
329
2e11
Oxidation Resistance
723
K
-554
723
1,762
Density
10.3
g/cm³
1.7
10.3
9,408
Hardness
150
HV
0.2
150
3,500
Corrosion Resistance
0.92
dimensionless (corrosion resistance index)
-1.1
0.92
1.1e6
Compressive Strength
830
MPa
8
830
2,625
Flexural Strength
690
MPa
11.4
690
2,897
Tensile Strength
690
MPa
3
690
3,000
Porosity
0
%
0
0
15
Absorptivity
0.4
0.02
0.4
0.6
Boiling Point
4,912
K
929
4,912
6,454
Absorption Coefficient
7.2e7
m^{-1}
5.9e5
7.2e7
9.9e7
Melting Point
2,896
K
133
2,896
3,865
Vapor Pressure
1e5
Pa
0
1e5
1.1e5
Thermal Destruction Point
2,896
K
133
2,896
3,865
Reflectivity
0.55
0.35
0.55
1
Thermal Shock Resistance
4e5
K
6.7
4e5
3.8e5
Laser Damage Threshold
1.8
J/cm²
0.27
1.8
1.6e4
Thermal Destruction
2,896
K
256
2,896
3,859
Specific Heat
251
J/(kg·K)
43.4
251
1,905
Laser Reflectivity
0.61
fraction
0.4
0.61
73.5
Thermal Conductivity
138
W/m·K
7.4
138
450
Thermal Expansion
4.8e-6
K^{-1}
4e-6
4.8e-6
31.7
Laser Absorption
0.43
0.02
0.43
4.2e8
Thermal Diffusivity
5.4e-5
m²/s
2e-6
5.4e-5
0
Ablation Threshold
2.1
J/cm²
0.09
2.1
4.3
Molybdenum surface magnification
Before Treatment
When we examine the contaminated molybdenum surface at high magnification, dark specks and uneven patches dominate the view. Layers of grime cling tightly, creating rough textures that obscure the base material. Scattered debris builds up in crevices, giving it a cluttered and worn appearance.
After Treatment
After laser treatment, the same surface reveals a smooth and uniform shine across its expanse. Clean lines emerge without any lingering spots or roughness. The material now appears polished and even, free from all visible buildup.
Regulatory Standards & Compliance
ANSI
ANSI Z136.1 - Safe Use of Lasers
IEC
IEC 60825 - Safety of Laser Products
OSHA
OSHA 29 CFR 1926.95 - Personal Protective Equipment
Molybdenum Laser Cleaning Laser Cleaning FAQs
Q: What are the best laser parameters (wavelength, power, pulse duration) for cleaning oxides and contaminants from molybdenum surfaces without damaging the base metal?
A: nanosecond pulses prevent micro-cracking. Given molybdenum's high reflectivity and melting point, I recommend a 1064 nm wavelength with nanosecond pulses at 5.1 J/cm² fluence. Notably, this ablates oxides effectively, while the 10 ns pulse width specifically minimizes thermal diffusion to prevent micro-cracking in the 2623°C base metal.
Q: How do you safely remove the white, powdery molybdenum oxide (MoO3) with a laser, given its low sublimation point and potential health risks?
A: Demands HEPA fume extraction. To safely remove MoO₃, employ a 100W nanosecond laser at 5.1 J/cm² for ablating the oxide with minimal heat buildup. Notably, this procedure requires industrial fume extraction featuring HEPA filtration, since the oxide sublimes around 700°C, generating hazardous inhalable particles that demand operator respiratory protection.
Q: Can laser cleaning be used to prepare a molybdenum surface for welding or brazing, and what surface quality (Sa) is achievable?
A: Achieves Sa below 1.0 µm. Laser cleaning particularly excels at preparing molybdenum for welding, removing oxides and hydrocarbons via ~5.1 J/cm² fluence. This thus yields a chemically active surface, with final roughness (Sa) typically under 1.0 µm—ideal for high-integrity brazing.
Q: Why is molybdenum sometimes difficult to clean with a fiber laser, and are there advantages to using a green or UV laser instead?
A: Higher absorption with green/UV. Molybdenum exhibits high reflectivity, particularly at 1064 nm, which renders standard fiber lasers inefficient. Green or UV wavelengths, notably, yield much higher absorption, thus enabling effective cleaning at lower power—around 100 W—with minimal thermal impact on the substrate.
Q: What is the risk of creating micro-cracks or a hardened layer on molybdenum components during laser cleaning?
A: Prevents micro-cracking via pulse control. By controlling pulses to a 10 ns duration and 5.1 J/cm² fluence, thermal stress is minimized. Particularly in brittle molybdenum, this thus prevents micro-cracking through a limited heat-affected zone and no surface hardening.
Q: After laser cleaning, how quickly does molybdenum re-oxidize, and are there recommended passivation methods to prevent this?
A: Re-oxidizes within minutes. Freshly laser-cleaned molybdenum re-oxidizes rapidly in air, notably forming a thin oxide layer within minutes. Thus, for long-term stability, process components under inert atmosphere or apply passivation treatment right after using your 1064 nm laser system.
Q: Is laser cleaning suitable for delicate molybdenum parts, like thin foil, wire, or sintered components, without causing distortion?
A: Low-power high-speed prevents distortion. Laser cleaning suits delicate molybdenum components well, but precise control remains critical. Particularly for thin foils or porous sintered parts, adopt a low-power, high-speed strategy—around 100 W average power at 500 mm/s scan speed—to minimize heat input and avoid thermal distortion. Thus, proper fixturing is essential for managing thermal stresses.
Q: What are the key differences in laser cleaning molybdenum compared to more common metals like steel or aluminum?
A: Demands precise fluence control. Molybdenum, with its notably high melting point of 2623°C and inherent brittleness, demands precise fluence control around 5.1 J/cm² to prevent thermal stress cracking—unlike more forgiving materials like steel or aluminum. Particularly for optimal cleaning, a 100W, 1064nm laser scanned at 500 mm/s manages reflectivity while avoiding substrate damage from excess heat.
Q: How do you verify the effectiveness of laser cleaning on molybdenum, and what analytical methods are used to check for residual contamination?
A: XPS confirms oxide removal. We first assess molybdenum laser cleaning effectiveness via visual inspection, notably for the restored metallic luster. For quantitative evaluation, XPS proves essential, specifically to verify oxide removal and measure residual carbon under 5 at%, while a contact angle test gauges the surface's renewed hydrophilicity.
