Hard-Facing Industry | MSSA

Hard-facing is commonly used to prolong the life of earth-moving equipment as well as being used to repair equipment components. By applying a harder material on top of the parent metal, it extends the life of the component which in turn saves maintenance costs and downtime. The hard-facing process also provides a means to help metals avoid corrosion and rusting, as well as deterioration through wear and tear.

Industries using the hard-facing process include, but are not limited to farming, construction, manufacturing, agriculture and earth-moving.

Drilling tips, No. A74 points, ultra wings, wombat points, post hole digger tips, dart sweeps, feed mixer knives (pictured above), stirrers, agitators, power blades, debarking blades, ploughing equipment, granulating system technology, excavator buckets and ripper boots are just an example of equipment that is subjected to the hard-facing process.

A wide range of our equipment can be used to provide a hard-face to a component: Tungsten Feeding, Arc Spray, Flame Spray, Laser Cladding, Puddle (Powder) Torch, HVOF and HVAF Systems.

Tungsten Grit Hard-Facing

The MSSA Tungsten Feeder (also known as a Pneumatic Tungsten Grit Feeder) is used for Tungsten Hard Facing with Tungsten Carbide. An air driven vibrator consistently feeds the tungsten fragments to your MIG torch. A tungsten grit application can prolong the life of a component by 3 to 5 times (depending on the application) which can make a substantial difference to running costs. 

Ground-engaging equipment is commonly associated with the tungsten hard-facing process. Ground engaging blades and ripper points on dozers and cat trucks are just some of the numerous applications that this process is used on.

When painted components are subject to hard-facing, the application area is often grit-blasted initially in order to provide a better surface for the tungsten to bind to. 

Ground Engaging Blades Grit-Blasted (Left), with Tungsten Application (Right)

For more information on the MSSA Tungsten Feeder, Click Here.

Saint Gobain Tuf-Cote®

When your application calls for a tough coating to protect against extreme process conditions, Tuf-Cote^® ropes provide the ideal brazed hard-facing solution to increase service life & performance of your parts & equipment.

Tuf-Cote^® rope is a brazed hard-facing material that creates tough wear-resistant coatings designed to increase the life of industrial components by 3 to 10 times. These ropes impart coatings that are extremely resistant to abrasion, erosion, corrosion & oxidation at both ambient & high temperatures, making them the ideal hard-facing material for oil & gas, power generation, drilling, mining, waste treatment, steel production & other demanding applications.

For more information regarding industry applications and grading on Saint Gobain Tuf-Cote®, Click Here.

Laser Cladding for Critical Component Repair - Duplex Stainless Steel

Laser cladding, a process that falls into the range of hard-facing solutions, can be used to increase corrosion resistance, wear resistance or impact performance of metallic components, using a method of applying a fully dense, metallurgically bonded and virtually pure coating.

Laser cladding can be used across a diverse range of industries. In this instance it was used to repair an EN8 steel drive shaft from a large CNC boring machine. The steel drive shaft had become worn in two bearing areas and was considered ‘unweldable’ by standard methods. Due to the critical dimensions of the shaft, and its relatively small size, it was crucial that distortion had to be controlled.

The Laser cladding process was an ideal solution for the EN8 steel drive shaft, as it produces a coating with a higher level of purity than other traditional welded hard-facing processes. Also, the very low heat input, associated with a laser, minimises distortion and results in a refined microstructure.

Materials - Main Deposit: Duplex stainless steel

Method

Preparation: Clean the worn bearing areas with alcohol to remove grease.

Equipment: Metallisation MET-CLAD system

Application of Laser Cladding

The two worn surface areas of the EN8 steel drive shaft were laser clad with duplex stainless steel and machined back to their original dimensions, enabling the shaft to be returned to the CNC boring machine. The laser cladding process utilises a precisely focused high power laser beam to create a tightly controlled weld pool into which a metallic powder is applied. The powder is carried by a stream of inert shielding gas, which is blown coaxially through the laser beam. The highly controllable nature of the laser beam allows fully dense cladding with minimal dilution and a perfect metallurgical bond. Due to the high level of accuracy and control, laser cladding enables the cost effective application of high performance alloys to tackle a wide range of engineering issues. Typical deposition rates are between 60 and 100 g/min around 3-6 kilograms per hour, depending on the material being deposited and the geometry of the work piece.

To apply a laser clad coating the cladding head has to be fed with four key things; a laser beam, process gasses, the metallic powder and cooling water. The Metallisation MET-CLAD laser cladding control console provides integration and control of the complex component parts. The MET-CLAD system is a simple to use control system with touch screen HMI and is based on the Metallisation HVOF and Plasma control concept. Using laser cladding to repair the EN8 steel drive shaft was the ideal solution, as the repair had to be of a high strength due to the load bearing pressure placed on the working component. The chemistry of the shaft was unsuitable for a traditional welding process due to its high carbon content and it was crucial there was absolutely no distortion. Finally, the low heat input associated with a laser clad coating, had a minimal effect on the base material strength.

Conclusion

Laser cladding is capable of producing coatings with a combination of excellent toughness and abrasive wear resistance and is ideal for Critical Component Repair work. In this instance, due to the low heat input in the laser cladding process, the duplex stainless steel and the EN8 steel drive shaft remained intact, without distortion. A critical requirement in this type of project.

Laser Cladding for Continuous Caster Rolls

Reason for Use: Increase wear resistance and provide an effective corrosion resistant barrier.

Laser cladding is a cost effective method of applying a relatively thin layer of an expensive, high performance alloy, which increases wear resistance and provides an effective corrosion resistant barrier.

Continuous caster rolls are used in the steel industry to cast continuous solid forms from liquid steel. The rolls are exposed to thermal fatigue, high temperatures, bending stresses, corrosion oxidation and abrasion.

The standard method of protecting caster rolls is by submerged arc welding with a 400 series stainless steel, which can suffer heat affected zone cracking between weld runs. Laser cladding the caster rolls is a cost effective method of applying a thin layer of a high performance alloy, in this case nickel based super alloys, to improve wear and corrosion resistance.

Laser cladding is a process that falls into the range of hard-facing solutions, which can be used to increase corrosion resistance, wear resistance or impact performance of metallic components, using a method of applying a fully dense, metallurgically bonded and virtually pure coating. Rolls that have been laser clad have been proven to last up to five times longer than the standard submerged arc welded rolls.

Materials - Main Deposit: Nickel based super-alloy

Method

Preparation

1. Old or worn rolls may need to be repaired prior to laser cladding using weld repair.
2. The rolls are pre machined to a size about 2mm smaller than the finished diameter.
3. The surface of the rolls must be clean and unoxidised and can be presented straight from the lathe.
4. If the rolls need to be cleaned prior to laser cladding, this can be done through degreasing or blasting.

Equipment: Metallisation MET-CLAD System

Application of Laser Cladding

The surface of the roll is laser clad with a nickel based super-alloy using a fine, accurately controlled laser beam, which results in an extremely strong wear and impact resistant coating.

The rolls are then stress relieved to reduce residual stress and finish machined to the required size. The laser cladding process utilises a precisely focused high power laser beam to create a tightly controlled weld pool into which a metallic powder is applied.

The powder is carried by a stream of inert shielding gas, which is blown coaxially through the laser beam. The highly controllable nature of the laser beam allows fully dense cladding with minimal dilution and a perfect metallurgical bond. The very low heat input, associated with a laser, minimises distortion and results in a refined microstructure. Due to the high level of accuracy and control, laser cladding enables the cost effective application of high performance alloys to tackle a wide range of engineering issues.

Typical deposition rates are between 60 and 100 g/min around 3-6 kilograms per hour, depending on the material being deposited and the geometry of the work piece. To apply a laser clad coating the cladding head has to be fed the appropriate with four key things; a laser beam, process gasses, the metallic powder and cooling water.

The Metallisation MET-CLAD laser cladding control console provides integration and control of the complex component parts. The MET-CLAD system is a simple to use control system with touch screen HMI and is based on the Metallisation HVOF and Plasma control concept.

The control console offers mass-flow control of the laser shielding and powder feed gas for repeatable cladding. The laser can also be housed and controlled within the cladding console up to 3kW or as a separate enclosure for larger laser sizes. The control interface for production operations is simple, but it can be drilled down to a great level of complexity for coating development. Repeatable operations are easily programmed or they can be linked to a barcode system for even simpler programming.

The process gases are mass flow controlled for repeatability of the coating process. Comparison of Coatings The image on the left, shows a laser clad surface after 118 ktonnes. The image in the middle, shows a sub arc welded surface after 63 ktonnes. In the right hand image, the top roll is sub arc welded and the lower roll is laser clad.

Comparison of Coating Processes

The above table gives a broad comparison of coating processes. The data shown is based on typical applications and parameters. There can be exceptions to this data, dependent on the specific applications and parameters, MSSA will be happy to offer advice for specific applications.

Conclusion

Laser cladding is a cost effective method of applying a relatively thin layer of an expensive, high performance alloy, which increases wear resistance and provides an effective corrosion resistant barrier. The minimal heat affected zone removes problems associated with weld decay. This means that laser clad continuous caster rolls can last up to five times longer than traditional submerged arc welded rolls.

Steel Clutch Lever Reclamation Using Flame Spray

Reason for use: Repair of worn pressed steel clutch levers.

The wire flame spray reclamation of clutch and many other automotive components has now become common practice. By using the flame spray process, considerable savings may be made over replacement costs.

Savings of up to 50% are common, where on large components savings of up to 90% may be achieved. The requirement for metal spray may be to repair an obsolete part, correct manufacturing errors or apply hard-facings onto areas prone to excessive wear in use.

Equipment: Metallisation MK 61 Flame Spray System

Materials: Molybdenum Wire

Cleaning

1. Steam clean if equipment available.
2. Degrease by solvent vapour if equipment available.

Preliminary Inspection

Check for cracks or faults taking lever below the manufacturers recommended operating tolerances.

Note: Metal Sprayed deposits do not import any strength to the base material.

Preparation

1. Preliminary Machining - Grinding or linishing may be used to remove any major scoring on level tips, blending in to form a uniform and concentric base.
2. Masking surfaces adjacent to area requiring treatment with a heavy duty masking tape. Thoroughly inspect for contamination prior to blasting.

Blasting

Thoroughly blast area to be metal sprayed with clean n° 30-36 Grade Aluminium Oxide Grit.

Application of Sprayed Coating

Masking

1. Apply No Bond masking fluid using a small brush to all areas adjacent to the area being sprayed. Ensure fluid is not applied to area being metal sprayed. (Small amounts of masking fluid on area to be sprayed can be removed with emery cloth).

2. Check thoroughly that area to be sprayed is free from contamination.

IMPORTANT: Areas to be sprayed should not come into contact with oil, grease, hands or any other form of contamination.

Note: Masking is not always required when spraying clutch release lever tips.

Spraying

Spraying should be as soon as possible after preparation and before any visible sign of deterioration occurs. A multiple of levers should be set in a fixture or laid in line ready for treatment.

1. Bond Coating
   
   A deposit of Molybdenum Wire is applied to a deposit thickness of 0.05mm-0.15mm (0.002”-0.006”) at a range of 75mm (3”). The spray stream should be at 90° to the surface being coated and traversed by hand at a surface speed of not less than 18 metres/minute (60 feet per minute).
   
   
2. Main Deposit
   
   Continue to spray the main deposit of molybdenum using the same spraying parameters as the bond coat but increase spray range to 100mm-150mm (4”-6”). Complete the spraying of the main deposit traversing the spray head to give a uniform coating over the lever tips. The final deposit thickness will depend upon the condition of lever tips prior to spraying and should be adjusted accordingly.

Note: If a hard final deposit is required, oxygen pressure should be increased after bond coat is completed.

Spraying Parameters of Metallisation MK61 for Molybdenum Wire

• Acetylene Pressure: 1.03 bar (15 psi)
• Oxygen Pressure: 1.9 bar (30 psi)
• Air Pressure: 4.5 bar (65 psi)
• Flowmeter Pointer Settings: Gas 5.5, Oxygen 2.25

Finishing

Under normal circumstances, it is possible to use the component in the as sprayed condition without any problems but for cosmetic purposes, a light polish may be required.

HVOF Alternatives to Hard Chrome Plating

Reason for use: To replace Hard Chrome plating particularly where environmental pressures have reduced its use.