Four Technologies that Beat Equipment Wear

Maintenance managers today have access to a wide range of technologies to repair, rebuild or otherwise extend the life of worn or damaged manufacturing production equipment.

Welding is by far the most popular equipment repair technique, but welding frequently introduces distortion or warping and creates difficulties that are as costly to overcome as the initial problem. This is especially true in applications where machined surfaces are involved.

Most repair processes, particularly those related to equipment wear, employ a specific process that adds material to a surface area to bring it back to size. Here are some guidelines to help maintenance managers choose the process that best meets their application needs in terms of time, effectiveness, and price.

LASER PROCESSING

Laser heat treating and laser cladding are two processes that can effect significant improvements in wear resistance, corrosion resistance, surface durability and hardness.

Heat-treating is a unique process that hardens high-carbon (>.4%) steel to 60 RC to a depth of 0.030” – 0.080” with virtually not dimensional distortion.

Laser cladding is a process by which powder is fed into the melt puddle created by a laser beam. The principal advantage of this type of component cladding is the low material dilution and the low input temperatures. Stainless steel, nickel, and cobalt alloys are the most frequently used powders, but a combination of these alloys with chromium or tungsten carbide can also be applied to provide surfaces that are highly resistant to severe abrasive conditions.

Laser processing is highly effective, and sometimes the only viable approach, for applications where a small area needs to be treated on a high-value component. The disadvantage of laser processing is its higher cost compared to conventional welding or even thermal-spray repairs.

High-value laser processing applications include:

Bearing areas for roller bearings (heat treating)

Pump impellers and housing rings (heat treating)

Large pump sleeves (cladding)

THERMAL-SPRAYED COATING

Thermal-sprayed coatings (or “flame-sprayed” coatings) comprise a wide variety of technologies that use powder or wire with high-velocity air or air-fuel mixtures to deposit a suitable repaired surface. The most commonly used materials are ceramics, carbides and metallics, which range from very soft (babbitt) to very hard (tungsten carbide). Depending on the work application and the coating process, these materials are applied in thicknesses from 0.005 to 0.025.

Thermal-spraying can be very effective for many different types of substrate materials, such as steel, copper, aluminum, nickel and cobalt based alloys. The process inputs less heat into the substrate than most other methods. The lower heat input offers major advantages when repairing precision parts where distortion is a risk.

Thermal-sprayed coatings are useful in low-impact and low stress- point loading applications. For example, tungsten carbide on an aluminum substrate provides low stress abrasion resistance on sliding components, Hastalloy “C” on a steel substrate provides effective corrosion resistance in many applications, and a 400-series stainless steel coating on low-carbon or 300-stainless improve the hardness (55-60RC) and durability of bearing seats.

Thermal-spray applications are used with great success on components in chemical processing, steel mills, aggregate production and large construction equipment, but have not found widespread use in mining applications. As noted, the key limitation of thermal-sprayed repair is its inability to withstand high-impact or heavy point loading. It is most effective in accomplishing thin to thick surface buildup and restoration of parts that are prone to distortion from heat input.

High-value thermal-sprayed coating applications include:

Bearing seats on shafts of all sizes

Differential housings

Pump impellers, housings, and shafts

Hydraulic rods and pistons

WELDING

The preferred method for most component repairs is welding, especially when the part has fractured with large gaping breaks or where large amounts of material are needed to rebuild a surface. Whether the welding process is electric arc, plasma or oxyacetylene, each method has a place in repair and rebuild.

MIG and stick welding are the most commonly used process, and MIG welding has made amazing advances in the past 10 years with improvements in inverters and rectifiers.

Plasma welding is particularly effective in welding nickel and cobalt alloys, especially where tungsten contamination can cause problems and where highly concentrated emery is needed.

The biggest benefits offered by welding technologies is that large amounts of material can be deposited and the processes are fairly simple. The major drawback facing these technologies is that the large amount of heat required frequently causes significant dimensional distortion. Welding is most effective in extreme wear applications where close tolerances are not required.

High-value welding applications include:

Pump impellers and housings that have been highly eroded

Steel crankshafts that are cracked or broken

PLATING

Plating can be a highly effective repair technique in applications where thin (0.001 – 0.010) coatings are needed for either wear or corrosion damage. Thicker coatings (0.030 – 0.050) of nickel can applied for build up and restoration of work parts, but these are usually more costly and time consuming than other processes.

Plating is a preferred approach when the component requires an especially fine surface and when the shape of the part is not conducive to finishing. The biggest drawback of this process is the risks it imposes for people and the environment.

High-value plating applications include:

Mixer bowls and paddles

Small parts with minimally undersized tolerances

OPTIMUM SOLUTIONS

Choosing the best approach for any equipment repair is more than simply comparing the cost to repair. A high-dollar repair technique might double or triple component life in some applications, but prove to be completely worthless in others. The correct choice can help you decrease your line down-time and decrease your operating costs. Talk to your equipment repair specialist about the best technique for the components you need repaired and the application they support.

If you don’t find the options you need, call Doug Gregory at BMR Group 800-468-1645. BMR Group, with facilities in Wolf Lake and Gary, Indiana, specializes in equipment repair for large and unique production equipment for multiple industries throughout the Midwest. Online at http://www.bmrgroup.net .