It’s no secret that wear and tear directly impacts a component’s performance.
In most mining applications, major mechanisms of wear include a combination of heat (eg. deformation) and friction (eg. abrasion), as well as various chemical processes (e.g. corrosion), which can result in compromised component geometry as well as rough surfaces that hinder smooth operation and eventually lead to failure.
Over the years various technologies have been invented and implemented in an attempt to reduce wear and increase component life – after all, preventative maintenance is far less costly than purchasing a new component outright. Those technologies generally involve installing a protective barrier between the component and the cause of wear: this can be in the form of hardened physical wear plates, but can also include plating and cladding technologies that apply thin protective layers of material onto the surface of any given part.
Hardchrome Engineering is a Melbourne-based company servicing industry all over Australia with its specialised material surface treatment technologies, including refurbishment for major parts up to 50t, hardchrome plating, laser cladding, vacuum furnace brazed wear plates, electroless nickel coating and many other protective and materials surface technologies.
Hardchrome Plating
Hardchrome plating is an electrolytic method of coating chrome for engineering applications using a chromic acid solution.
Electrolytic cells are a type of electro-chemical cell that use electrical energy to drive a non-spontaneous redox reaction. By connecting the component to be plated to an electricity source, it is turned into a cathode and lowered into a bath of chromic acid to be shared with an anode where the acid is broken down and the resultant chromium is deposited evenly onto the cathode until a desired thickness is reached – anywhere between 0.25 to 1000 micron thick.
It is considered a ‘cold’ process with operating temperatures of 50-60o ensuring there is no detrimental effects to the physical or mechanical properties of the base material.
By selectively covering certain areas of the component with a temporary wax coating, the chromium is deposited onto the targeted areas only while the other areas remain protected.
Once the redox reaction is complete and the desired thickness of material has been deposited onto the component (cathode), the component geometry is then refined with a grinding process before being polished for completion.
The benefits of chrome plating go far beyond the pleasing aesthetic. Electro-deposited chrome is extremely hard with hardness values of 850-1050 HV (“HV” is the Vickers Hardness unit) which is comparably better than hardened steel.
The low coefficient of friction however is approximately half that of steel, which makes it an excellent coating for wear-resistant and abrasion-resistant applications such as molds, dies, bearings, seals, and sliding components.
Due to the hardness and low frictional properties, the hard chrome is also extremely resistant to abrasive and erosive wear, extending the life of components up to ten times in most cases. It is also corrosion- resistant due to being resistant to most oxidising and reducing agents (with the exception of chlorides and halides).
The best part about hard chrome plating is that the hard chrome deposits are designed to be an easily-replaceable sacrificial wear layer. The hard chrome plating is easily removed using appropriate chemical strippers without detriment to the base material, meaning a component can be stripped and re-plated when wear begins to show, prolonging the life of the base component significantly.
Hardchrome Engineering’s Melbourne facility currently services major OEM suppliers all over Australia, and has the capacity to apply hardchrome plating to componentry such as press tools and punches, to hydraulic and pneumatic piston rods and cylinders weighing up to 50t and up to 25m long (for example large Westrac pull-down cylinders commonly found at ports and loading barges).
Laser Cladding
Laser cladding is a process by which a powdered metal or alloy is melted by laser onto the surface of a new or damaged component for the purpose of wear, abrasion or corrosion protection.
With a choice of four high-powered 6Kw and 4kW laser systems, the substrate material is melted and powder is injected into the molten pool which then metallurgically bonds with the surface material. Similar to laser welding, there is no coating to peel off, cracking or defects afterwards but unlike standard hot welding the precision and localized nature of the laser means that the component does not bend or warp due to internal stresses induced by heat.
Various types of materials can be used to coat a component part, including tool steels, stainless steels, tungsten carbide and nickel powders as well as Stellite® powders.
Tungsten carbide is one of the hardest, most durable and wear-resistant materials commonly found on the contact points of mining machinery and plant – bucket teeth, percussion drill bits, wear plates, and barrel teeth on surface miners and terrain levelers.
By laser cladding tungsten Carbide layer onto any component in high-wear environments, the time before failure dramatically improves. The tungsten carbide particles, mixed in with a nickel matrix, bring the hardness value up to 2200 HV and as it can be applied on both outer and inner-diameter surfaces, any part can be made extremely resistant to wear and tear.
The coating created by laser cladding is virtually impenetrable.
Hardchrome Engineering has two 6Kw and two 4kW lasers with various sized cladding heads and multiple six-axis robots, vertical and horizontal positioning equipment, which are fully portable – meaning they can bring the lasers to sites through its subsidiary company Hardwear Laser Surfacing.
This comes in extremely handy for instances where parts are costly to disassemble and transport across borders (for example turbine blades, valve seats, valve chests, etc).
Some major uses of the in-situ laser cladding technology include power stations, mines, steel mills, rail industry, oil and gas industries and four-axis CNC systems.
Applications include ground engaging tools (GETs), wear plates, truck bodies, slurry tubes, mill liners – the works. The technology can even be used to bring parts back to OEM dimensions after episodes of serious wear and tear, and followed up with a round of hardchrome plating to improve the life even further.
Hardchrome Engineering metallurgists are always prepared to discuss clients’ technical needs and offer metallographic reports for laser processed parts. They are also keen on getting involved in R&D projects on laser processing.
| Advantages of Laser Cladding | ||
| Minimal heat input to the part | Little or no distortion of parts | Perfect metallurgical bond between deposit and the substrate |
| Deposit a wide range of different metals on any metal part | Economically competitive process with fast turn around times | No cracks. No porosity. No delamination’s. No defects. |
Hardfuse Wear Plate
A proprietary invention developed in-house, the hardfuse wear plate uses similar metal/alloy powders used in the laser cladding process, but instead is fused inside a vacuum furnace for rapid production.
Even with the localised heat of the laser cladding, with large wear plates occasionally the larger surface are does lead to buckling and bending. By coating the plates using a powdered spray and placing them inside the furnace, the temperature is completely uniform throughout the reaction and so any potential bending or buckling is removed from the equation.
The plates are currently coated with a 3mm thick layer of cladding but can be thickened upon request.
Electroless Nickel Plating
Hardchrome Engineering also offers a chemical plating service known as Electroless Nickel Plating, a non-electrolytic, auto-catalytic, immersion chemical plating method for nickel-phosphorous alloy onto the surface of metal components.
Unlike electro-plating technologies such as chrome plating that requires some machine finishing, this method does not require that an electric current is passed through a chemical bath using anodes and cathodes.
The reduction of the metal solution onto the substrate is achieved through an autocatalytic reduction (ie. the chemicals and metals drive their own reaction) – this type of reaction results in an even layer of nickel being plated onto the substrate, as there are no inherent electrical current differences caused by uneven geometry. The process itself is considered a cold process with temperatures only reaching 85-95o.
Electroless Nickel barriers provide excellent corrosion resistance (only being susceptible to extremely strong oxidising agents) and a low coefficient of friction that makes it suitable for sliding parts. Hardchrome Engineering state that it passes a 1000-hour salt-spray test. Applications include hydraulic and pneumatic components, pumping equipment, valve components, automotive components, and even chemical equipment.
Factory and Service Capacity
Hardchrome Engineering’s 3000m2 Clayton and 21,000m2 Yallourn facilities are equipped to take on any sized task, with a vast array of technology, equipment and processes available to significantly extend the life of expensive equipment.
From small machine components to large mill rolls for the steel and aluminium industries, Hardchrome Engineering specialises in providing customised solutions for any application with every job being specifically tailored to meet the exact specifications of clients.
Company Profile
Established in 1968, Hardchrome Engineering and subsidiary Hardwear Laser Surfacing have an extensive capacity for large scale application of surface material protection technologies.
With a large team of fully trained technicians, metallurgists and chemical engineers at the helm, the company is able to maintain its ISO 9001 quality rating.
Hardchrome Engineering also offers a plethora of related surface reliability engineering solutions, including hydraulic service and cylinder repair, laser welding, electroless nickel coating, ceramic diffusion coating with Sermetel and Alseal, nitrex/nitriding, vacuum heat treatments, vacuum brazing, neo chroming, application of nickel teflon as well as texturing and surfacing. Ancillary service offerings also include classic boiler making and machining services.
Currently servicing major original equipment manufacturers and clients all around Australia, Hardchrome Engineering ensures that the technology it uses is capable of refurbishing parts nearly identical if not better than the way the parts left the OEM factory.
The company has the capacity for anything up to 50t. There is no chrome job or laser cladding job it wouldn’t take on – no job is too big or too hard.
Source:
Ph: +61 (0) 3 9561 9555
E: [email protected]
W: www.hardchrome.com.au
