Metal parts may seem indestructible, but part failure is a common challenge across dozens of industries. From mining to construction, many of your machinery’s most crucial parts and components fail not because of fracture but because of wear and tear. Weld overlays are a commonly used practice that can help you protect your most valuable assets from the destruction waged by daily corrosion and abrasion. 

What Is A Weld Overlay?

Weld overlays refer to the process of improving the wear resistant properties of base metals in order to make them stronger and more durable. Sometimes referred to as hard surfacing, surface welding, or even cladding, this process is achieved by welding to the base metal through the use of specialized electrodes, powders, or filler rods. Typically, weld overlays are applied as a way to make the original part or piece of equipment more durable and extend its lifespan. Additionally, overlays can increase the component’s ductility, hardness, corrosion resistance, and erosion resistance. The weld material can usually be applied as a solid surface or in a waffle, herringbone, or dot pattern.

What Are the Benefits of a Weld Overlay?

Companies choose to apply weld overlays to their products and parts for a multitude of reasons, including:

• Increased wear and impact resistance: Parts that have had a weld overlay will be stronger and more resistant to abrasion, erosion, and heavy impact. 

• Increased equipment lifespan: Overlaying prolongs equipment life anywhere from 30–300% depending on the specific application, thus avoiding costly replacement. 

• Corrosion protection: Depending on the specific overlay alloy utilized, the component can display increased corrosion resistance.

• Reduced equipment costs: Weld overlays offer substantial savings, as it usually costs 25–75% of the price of a full replacement.

• Reduced downtime and inventory of spare parts: Due to the increased part lifespan, fewer unplanned shutdowns are experienced, and there is less need to keep stockpiles  of spare parts around as worn parts can simply be rebuilt.

What Base Metals Can Have Weld Overlays?

There are a wide range of base metals that can have a weld overlay applied. Typical metals that work well with overlays include but are not limited to nickel-base alloys, stainless steel, manganese steel, and carbon and alloy steel. However, before kickstarting any overlay procedure, it’s important to determine exactly what material the part is made of because this determines the pre-heat and post-heat temperature that should be applied and if there needs to be a PWHT (Post Weld Heat Treat) performed.

What Industries Utilize Weld Overlays Welding?

While weld overlays are incredibly popular in the manufacturing industry due to the high number of parts made from low-alloy and higher-carbon steel, overlays can also be leveraged by many other sectors, especially those that utilize “heavy wear” equipment. 

From farming to construction and more, overlays can be beneficial in fortifying parts that need to resist repeated impacts, corrosion, and abrasion over time:

• Mining and Construction: Earthmoving buckets, blades, and other excavation components like plows and crushing rolls can all be strengthened by overlays.

• Agriculture: Overlays can help repair farm equipment such as rollers and plowshares. 

• Energy: Pieces such as turbine blades and other power generation components can be used longer thanks to overlays.

• Oil and Gas: Several heavily exposed equipment pieces like drill bits, collars, stabilizers, and reamers can be fortified through overlays.

• Pumps: Parts such as impellers, wear rings, bushing, and case rings can all be improved with overlays to help with wear and corrosion.

What Are the Types of Weld Overlays?

A number of overlay welding processes may be employed depending on the part and the specifications of the damage. 

The most commonly employed methods of applying weld overlays utilized by HTS Coatings include:

Tungsten Inert Gas (TIG) Welding

Tungsten inert gas welding (TIG)—also known as gas tungsten arc welding (GTAW)—is a popular overlay method within the arc welding family. It uses non-consumable tungsten electrodes to produce a weld and is commonly employed for alloys, such as Stellite® or Colmonoy, or to weld 316 stainless steel to other stainless components. TIG can be applied to components like sleeves, bushings, augers and screws, wear rings, and print cylinders. 

Metal Inert Gas (MIG) Welding

This type of overlay is characterized by a welding process in which an electric arc forms between a consumable MIG wire electrode and the workpiece metal. During MIG, the intense heat causes the two to melt and join. MIG welding is also sometimes referred to as gas metal arc welding (GMAW) and is typically used for repairing cracks, holes, or pieces damaged by erosion. HTS Coatings typically uses MIG welding and flux core welding to build up heavy wear sections of steel or stainless steel.

Plasma Transferred Arc (PTA Welding)

Also known as an alternative to laser cladding in some applications, plasma transferred arc (PTA) welding uses powder metal alloys to increase surface hardness and durability. Typically, PTA is used for restoring direct-impact cutting tools, repairing valve stems and seats, protecting pump wear rings, rebuilding mud motors, and other component repairs. This process is suitable for stainless steels, cobalt-base alloys, and tungsten carbide.

Brazing

This technique is generally implemented for cast-iron components, where traditional welding is not suitable. Brazing refers to a metal-joining technique that brings components together by heating up the substrate and flowing a filler material into the joint. Unlike welding, brazing does not involve melting the workpieces. This procedure is ideal for two pieces that do not weld together easily. Generally, brazing is used for pump and gear housings as well as glass work deflectors and/or brass or bronze components. 

HTS Coatings Weld Overlay Welding Solutions

Weld overlays may have a reputation as a specific and complicated process. Nevertheless,  when executed correctly, overlays can be an indispensable factor in reducing unplanned downtime and extending the lifespan of your most valuable equipment. From saving thousands of dollars in repairs to increasing wear and corrosion resistance, overlays can provide some much-needed TLC to your most frequently used equipment. With ASME Section IX compliant WPS (Weld Procedure Specifications), PQR (Procedure Qualification Records), and WPQ (Welder Performance Qualification) records, HTS Coatings draws upon decades of in-depth experience and knowledge to provide tailored weld overlay solutions to clients across industries.