New laser welding techniques can repair the fine blades of an impeller (above) and jet engine blades (below).

The blades and vanes of a jet turbine engine are subjected to intense heat, continually varying operating conditions and the occasional impact with dirt, gravel and even birds. As a result, they need to be repaired and replaced on a regular basis and the tool of choice for repairing them has become a CO2 laser welding system.

"Blades and vanes are about 30 percent of the cost of a new engine but 85 percent of the cost to maintain that engine," said Roger Hayes, president of Huffman Corp. in Clover, S.C. Using our laser powder fusion systems, an engine repair facility can restore a blade or vane to like new condition in a few minutes instead of having to spend $2,500 or more for a new one."

Huffman has more than 60 of its systems being used by component manufacturers and repair facilities such as General Electric, Pratt & Whitney, Rolls-Royce of North America and Honeywell International. Huffman also has developed systems for manufacturing medical implants and tool inserts. Huffman systems use a process called laser powder fusion.

Powder fusion systems are designed to add material to existing parts or to create new parts by adding one layer of material on top of another until the desired shape is achieved. The part is then machined to final tolerance and finish.

At the heart of every Huffman system is a laser. Huffman has used both CO2 and nd:YAG (neodymium-doped yttrium aluminum garnet) lasers. CO2 lasers use a gas mixture of carbon dioxide (CO2), nitrogen (N2), hydrogen (H2) and helium (He). The specific proportions will vary from laser to laser. The gas is put into a discharge tube and an electric current is run through the mixture to generate a beam of infrared energy. The beam is used to melt the surface of the part being worked on and, in the case of laser powder fusion systems, the powdered metal being added to the part.

This process causes the CO2 to decay, and as it decays the amount of energy generated by the laser diminishes. When the amount of energy being generated falls below the required level the gas mixture in the tube must be replenished.

Laser powder fusion systems have also proven to be very effective at putting hard surfaces on parts, especially very large parts.

Gremada Industries in West Fargo, N.D. (www.gremada.com) has been using laser powder fusion systems to repair worn surfaces on large Caterpillar vehicles for more than 11 years. "We are a contract company for Caterpillar," said Mike Goerdt, Gremada project manager. "A lot of what we do is on the final drives of the huge carrier trucks used for mining. We get the drives in, disassemble them and re-pair or replace parts as needed. We are able to repair worn surfaces by putting a layer of hard material on and then machining the part back to original tolerance. We use as 6 kW CO2 laser here in Fargo and an 8 kW laser in our Houston operation." Gremada's Houston operation services the oil and gas industry.

Another company, RPM & Associates in Rapid City, S.D., (www.rpmandassociates.com) uses a laser powder fusion system to repair rotating shafts in the mining and power industries. "We use our system to repair the bearing areas on shafts that wear out," said Nick Wald, project manager. "We work on shafts as small as 1 foot long and 6 inches in diameter up to shafts 19 feet long, 20 inches in diameter and weighing about 20,000 pounds. We put a new layer of material on the worn areas of the shafts and then machined the shafts back to final tolerance. We've also done some free-form work. We can take a 3D model and fabricate an entire part layer by layer to near net shape and then machine it to final shape."

This ability to create near net shape parts directly from a CAD drawing is beginning to be used in a wide array of industrial applications. Because the process can use almost any metal or combination of metals, it can be used to fabricate parts that have traditionally been very difficult, expensive or impossible to fabricate, and to do it in a cost-effective manner. For example, titanium hip joint replacements can be fabricated more quickly and for less cost than the traditional method of machining the part from a solid block of titanium.

Laser powder fusion technology has recently moved from the laboratory to the shop floor but it is just one type of laser welding system in use today. Far more common are the industrial welding units used to manufacture a wide range of products from micro machines to automobiles to oceangoing ships. CO2 lasers are also used for industrial cutting.

Industrial fabrication, welding and cutting are not the only areas where CO2 lasers are being used effectively. Surgeons use CO2 lasers for a cosmetic procedure sometimes called "laser peel". The laser is used to remove areas of damaged or wrinkled skin layer by layer and is becoming more widely used as a substitute for chemical peels and dermal abrasion.

CO2 lasers are not the only type of lasers being used, but their continuous power capability, high-efficiency, ease of construction and relatively low cost compared to the amount of energy produced make them very attractive for a wide range of applications.

Laser manufacturers can optimize laser performance by adjusting a number of parameters including: discharge tube length, diameter and a wall temperature; electrical discharge control and current density; optical mode control; wavelength control; output coupling; and gas mixture.

The exact combination and purity of gases used in the gas mixture are a major determinant in the amount of energy generated. Users of CO2 lasers need a custom mixture of laser manufacturer specified gases to replenish their lasers. The more a CO2 laser is used the quicker the CO2 in the gas mixture is depleted and needs replacement.

There already are hundreds of CO2 lasers being used in industrial and medical applications and that number will continue to grow. Every one of those lasers is a sales opportunity for gas distributors and as the number of applied lasers increases so too will the number of sales opportunities.