Engineering Coatings

While anti-corrosion applications are the most common use for metal spray, the technology is also frequently used in engineering applications to increase wear resistance in the life of components and also to reclaim crucial parts that have worn or have been damaged. The benefits of thermal spraying for metal repair and reclamation are many and varied.  The major driving factor is one of cost. With many individual parts costing thousands of dollars, the ability to repair areas offers a major cost saving. Also, coatings of materials that have different properties than the base material can be used to provide localised increases in wear protection.

Wire stocked can be viewed here.

Waitaki Turbine Shaft

A hydro power station works by harnessing the energy from falling water. The water held above the power station in a lake or reservoir is channeled through pipes or penstocks to the turbine. The turbine extracts the energy from the water, turning it into mechanical energy that spins the generator rotor creating power. This turbine shaft required a 1050mm long bearing surface to be built up. Weighing in at many tons and over 3.3M long this made for a large job under tight deadlines. The shaft was mounted in a lathe, pre machined then with the aid of a mechanical traverse a thermal sprayed bond coat was applied followed by final coat of Iron, Nickel, Chrome, Boron, Silicone alloy, sealed and finished to fine tolerances.

Engine Parts

For either fast turn around, unavailability of new parts or as an alternative to high cost replacements, thermal sprayed coatings are applied to crankshaft journals, cylinder head mating faces, bearing faces, hubs and shafts in the automotive and marine industries.

Caterpillar dump trucks used in a Southland mine have a loading capacity of around 100 tons. The life-span of a rear axle is about 13,000 hours which is equivalent to about 2 1/2 years work. The axles are expensive to replace and difficult to obtain, so the question was - could their life span be increased? A specialist metal spray contractor from Dunedin arc sprayed the rear axle. Due to the nature of the process, the base material of the axle was not placed under any risk of metallurgical change during the process. After surface preparation, a bond coat of Ni - Al - Moly was arc sprayed giving a tensile bond strength of over 7,000 psi. This bond coat was followed by a customised alloy. After the coating was completed, the axle was machined to a fine finish and close tolerance. The first axle was arc sprayed around 20 years ago and many other axles have been repaired to date, at a cost of $1,500 each and a turnaround time of 13 hours. 

Yacht Propeller Shaft

The 52 Metre, 1902 schooner Shenandoah had its propeller shaft reclaimed in Auckland. To resist continuous salt water immersion a stainless steel with boron and silicone was needed for the gland seal area. Quite often the applied material has better performance than the original substrate.