Laser Surface Melting
Laser Surface Melting (LSM) is a focused laser treatment that melts only the top layer of a substrate and rapidly re-solidifies it to form a refined surface microstructure. It improves surface quality, reduces roughness, and can increase hardness or wear resistance without adding alloying elements or changing bulk chemistry.
On the shop floor, LSM is used as a controlled post-processing or surface-engineering step on localized regions where only a thin surface layer needs modification. A high-power focused laser, usually with inert gas shielding, melts a clean, shallow layer while keeping the heat-affected zone small. In additive-manufacturing workflows, laser remelting of printed metal surfaces lowers roughness before downstream finishing; one study found optimized remelting parameters of 250 mm/s scan speed, 105 W laser power, and a 65.40 µm beam spot diameter. LSM is non-contact, software-controlled, and highly localized, making it useful on precision parts where grinding or aggressive machining would distort thin sections. It is not a replacement for final dimensional machining on critical fits; rather, it is a pre-finishing or functional-surface modification step that reduces subsequent polishing, grinding, or sealing-surface finishing.
- Overheating and excessive melt depth: Excessive power, dwell, or overlap deepens the melt pool beyond the intended layer, causing warping or an oversized heat-affected zone. On thin parts, thermal expansion and shrinkage can push geometry out of tolerance.
- Oxidation or contamination of the melt pool: Poor shielding gas or an uncontrolled atmosphere oxidizes the molten surface, degrading finish and property improvements. This appears as discoloration, inconsistent reflectivity, and poor wettability for later coatings.
- Poor parameter selection on AM surfaces: Remelting without tuning scan speed, power, and spot size can reproduce the as-built texture or cause balling and unstable melt tracks. Additive parts often still need post-processing after LSM to reach target roughness.
Is Laser Surface Melting the same as Laser Surface Alloying or Cladding?
No. Laser Surface Melting melts only the substrate surface and relies on rapid resolidification, while alloying and cladding add external material or chemistry to the melt pool.
Does Laser Surface Melting change bulk properties?
The intent is to modify only the near-surface region with little thermal penetration, so bulk properties are largely preserved when parameters are controlled correctly.
Where does Laser Surface Melting fit in a manufacturing route?
Typically after primary forming or additive build and before final finishing, especially where a localized functional surface needs improved roughness or wear behavior without full re-machining.