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Laser materials processing includes technologies such as laser cutting, welding, cladding and hardening, among others.
Laser cutting was the first, and to date, the most successful machining application to have evolved from the invention of the laser.
Laser cutting offers the following advantages:
- Flexibility - Laser profile cutting is a computer-controlled process, which does not require hard tooling. Design changes are therefore easily and quickly implemented.
- No tool wear - Laser cutting is a thermal process, which does not involve mechanical contact. This is important where hard, flexible or brittle materials have to be cut.
- Fine detail - The laser ‘tool’ has an effective diameter of some 100 - 200 microns (a micron is one millionth of a metre). This is an important advantage in the case of profiles with fine and intricate detail, and where small holes need to be drilled in hard or flexible material.
- Edge quality - Low surface roughness and small heat-affected zones are possible without any blurring. This eliminates the need for post-processing.
Laser cladding is a new weld surfacing technology recently introduced to the South African industry. The process involves the deposition of any weldable material on the surface of a metal substrate using a laser beam. This technique can be used on both new and worn products and is typically used to weld repair worn or damaged surfaces, hard-face wear-susceptible materials or weldclad surfaces susceptible to corrosion, oxidation, wear or a combination of these.
This flexible technique allows welding consumables to be deposited in either powder or wire form. Weld deposits are fully fusion-joined to the substrate material in thicknesses ranging from 0.1 to several millimetres – multiple layers can also be deposited. The very low heat-input rate associated with laser cladding results in extremely low dilution with the substrate, also resulting in relatively small heat-affected zones and minimal distortion.
Typically, laser cladding would be used where wear and corrosion resistant layers are required, for example, on valves, pumps, turbine blades etc. In addition, it could be used for the repair and modification of valve seats and shafts (e.g. in power plants), gears and drive shafts and also for turbine blades.
Laser welding is noted for its high levels of productivity that are achieved through the ability to combine high welding speeds with excellent weld quality. Weld quality is assured through the unparalleled control that the laser welding process offers. It is essentially a process where the laser acts as the heat source. The precision and control with which the laser delivers heat to the process is at the heart of the many important advantages that the process offers. The fundamental property of laser welding, which is responsible for the significant advantages of this process, is the highly localised heat input that a focused laser beam delivers. This feature enables the high welding speeds and exceptionally low heat input that laser welding is renowned for.
Laser hardening is a metal surface treatment process complementary to conventional flame and induction hardening processes. This process is ideal for treating small areas on sensitive, high-value components. Selective areas can be hardened without affecting the surrounding material; minimal heat input results in limited distortion and reduces the need for additional machining; the treatment depth is accurately controlled and highly reproducible. In laser hardening a high-power laser beam is used to heat a metal surface rapidly and selectively. The self quenching effect of the base material produces the rapid cooling rates required for the hardening process to produce hardened depths of up to 2.5 mm. The process is environmentally friendly as it eliminates the use of water or oil for quenching.
The high hardness of the micro-structure provides improved properties such as wear resistance and increased strength. Laser hardening is used by various industries, for example, in the automotive industry it is used for drive shafts and stub axles, car door torsion springs, synchronous gears and gear selectors, components in auto steering pumps etc.
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