Application of Laser Treatment in Manufacturing and Maintenance

• 1
  What matters before you specify a laser
• 2
  Where the application of laser treatment replaces a conventional step
• 3
  Laser welding versus TIG: choosing by joint and alloy
• 4
  Laser cladding and repair in equipment maintenance
• 5
  Which alloys take laser treatment well
• 6
  How laser work fits into a CNC process chain
• 7
  Laser process compared with the conventional alternative

Laser treatment enters a shop in four places: it creates a surface (marking, cladding, hardening), it joins two parts (welding), it separates material (cutting), and it repairs worn geometry (cladding plus remachining). Each of those replaces a different conventional step, so the decision is not whether the shop owns a laser but which step the laser replaces on that specific part.

Take marking. A fiber laser marks a stainless 316L housing with a serial number at a minimum character height of 1.5 mm, and that mark survives bead blasting and passivation. A stamped number would dent the wall and a printed label would fall off. Here the laser replaces stamping, and no post-machining is needed because the mark is shallow.

Hardening is different. A 0.5–2 mm case on a 4140 guide rail can be produced with a defocused beam and a controlled travel speed, and the part keeps its core toughness. But the treated zone grows by a few micrometres and the surface roughens, so a finish grind usually follows if the rail has to slide on a bearing.

Laser welding fuses metal with a focused beam, so the heat-affected zone stays narrow. On a 1.5 mm 304 stainless bracket, a keyhole weld at roughly 1–2 kW and 2–4 m/min produces a seam a few tenths of a millimetre wide with little distortion. TIG on the same bracket would spread heat over several millimetres and pull the part out of flat.

The trade-off is fit-up. Laser welding tolerates a gap of roughly 0.05 mm, not 0.3 mm. If the two halves are sheared and not machined, the beam passes through the gap and the joint fails. Shops that run both processes usually machine the mating faces to ±0.05 mm before welding.

Rapid cooling can trap porosity and cracks in thick sections or in alloys like 7075. Preheating, a filler wire, or a hybrid laser-arc setup reduces the cooling rate. For a 6 mm 6061 plate, a hybrid process with an arc trailing the beam gives a wider heat range and fewer pores than a pure laser pass.

• 1
  Choose laser weldingThin sections, tight distortion limits, high seam count, machined fit-up.
• 2
  Choose TIG or MIGThick sections, loose fit-up, field repair, low part count.
• 3
  Watch 7075 and 2024These alloys are crack-sensitive; a filler wire or hybrid arc helps.

A worn shaft, a scored hydraulic rod, or an eroded pump housing can be rebuilt instead of remade. Laser cladding sprays or feeds metal powder into the melt pool, so the deposit bonds metallurgically to the base and adds little heat to the part. A 0.5–2 mm layer of 316L or a nickel-based powder restores the diameter.

The base metal has to be sound. If the shaft is cracked through or the housing has fatigue damage below the worn zone, cladding just buries the defect. Magnetic particle inspection before cladding is a cheap check. After cladding, the deposit is typically at Ra 6–12 μm, so a turning or grinding pass brings it back to size.

The economics work when the part is expensive, the lead time is long, or the geometry is unobtainable. A one-off impeller that takes weeks to source is a good candidate. A standard 1018 bushing that costs less than the cladding setup is not. In those cases, the shop machines a replacement instead.

Carbon and low-alloy steels are the easiest group. 1018, 1045, 4130, 4140, and 4340 all absorb near-infrared light, weld cleanly, and harden predictably. 4140 is common for laser-hardened guideways and 4340 for shafts that need a tough core with a hard skin.

Stainless steels behave well for marking and welding. 304, 316, and 316L resist corrosion after laser marking because the oxide layer that forms is thin. 17-4PH can be laser hardened to a higher surface hardness, but the aging treatment has to come first or the laser pass will alter the temper.

Aluminium, copper, and brass need more power and better shielding. Bare aluminium reflects most of the beam, and copper conducts heat away fast. Both are weldable with a fiber laser, but expect higher power, tighter focusing, and a shielding gas. Titanium TC4 (Ti-6Al-4V) must be shielded with argon to avoid oxygen pickup, which embrittles the weld.

Plastics are marked, not welded or hardened. ABS, PC, and POM take a laser mark with a suitable additive or a wavelength that the polymer absorbs. PEEK can be marked and, in some grades, laser welded, but the process window is narrow.

Most laser operations do not finish a part. They sit between machining steps. A shaft may be turned, laser cladded, then ground back to size. A bracket may be machined, laser welded, then stress-relieved and finish-machined on the joint face. Planning the chain matters more than the laser itself.

Tolerances are the reason. GreatLight holds ±0.005 mm (±0.0002 in) on CNC-machined features and Ra 0.2–0.8 μm on fine finishes. A laser-clad surface starts far coarser, so the drawing has to allow a finishing pass. If the drawing calls for the final tolerance on the clad surface, the process chain is wrong.

Inspection closes the loop. A laser-hardened zone can be checked with a hardness traverse on a cut coupon, and a weld with a penetrant or radiographic check. GreatLight inspects 100% of parts before shipment, with raw material checks, in-process monitoring, and final inspection, and reports are available on request.