Numerous Base and Coating Material Combinations

Thermal Spray Processes
In recent years, thermal spraying has become increasingly important, both in the manufacturing of new parts and in the repair of existing parts.
Thermal spraying is a surface coating technology which combines a variety of positive characteristics.

Numerous base and coating material combinations
High grade materials coating onto lower cost base materials
Repair instead of replace expensive components
Many thermal and mechanical energy process combinations for just the right effect.

Two types of energy are required to spray on a coating: thermal and kinetic. Both of these energies are generated trough gases.
The move towards dense layers has resulted in equipment where the kinetic energy rises in line with reduced thermal input. The evolution of high-velocity thermal spray methods has led to Cold Gas Spraying where the surface material is propelled and plasticized as it hits the substrate, thus combining with the basic material. This procedure is similar to explosion welding.
Spraying is a real money saver and easy to carry out. For an exact surface finish, all you need is a flame, an electric arc/plasma or laser and the right coating material. It improves resistance to wear, corrosion and heat. You can even use this process to increase or decrease friction or change the electrical properties of the surface. Damaged surfaces can be repaired and faulty parts can be redimensioned. In most cases, the surface can easily be post –treated.
Flame Spray & HVOF
In flame spraying the coating material does not come into direct contact with the oxyacetylene flame. The material is therefore not melted directly by the flame, but by heater air and radiation heat.
Alternatively, high velocity oxy-fuel (HVOF) involves a continuous gas combustion under high pressure in a combustion chamber. The spray material, in powder form, is fed into the central axis of the chamber. The high pressure of the oxy-fuel gas mixture produced in the combustion chamber- and the expansion nozzle - in turn produces the desired high flow velocity in the gas jet. The fuel gases which can be used are propane, propylene, ethene, acetylene, and hydrogen.
Applications include sliding surfaces, roller, machine parts and all anti-wear protection parts
Plasma & Wire Arc Spraying
In plasma spraying, the spray material, in powder form, is melted by a plasma jet in or outside the spray gun and propelled onto the work piece surface. The plasma is produced by an arc which is constricted and burns in argon, helium, nitrogen, hydrogen or their mixtures

In the plasma transferred arc (PTA) process, the surface of the work piece is surface melted. A high density plasma arc serves as the heat source and the metal powder as the surfacing material. The arc is formed between a non-consumable electrode and the work piece. The plasma is generated in the plasma gas, between the central tungsten electrode and the water-cooled anode. The entire process takes place in the atmosphere of a shroud gas

Cold Spray
In cold spraying, the kinetic energy (particle velocity) is increased and the thermal energy reduced. In this way it is possible to produce spray coatings which are virtually free of oxides.
Laboratory investigations show that cold spray coating have extremely high bond strengths and are exceptionally dense. In cold spray processes the powder requires a temperature of only a few hundred degrees. Coated substrates reveal no material changes due to thermal influence.
Applications are still being developed. Current uses are found in the automobile industry, anti-corrosion protections and electronics, for example

Supply System for Cold Spray Applications, DESY® 300/100
In this system, the nitrogen is compressed up to 4000psi (275 bar) in the liquid state. After the DESY® 300/100, the liquid nitrogen is evaporated in a high pressure evaporator.
For pressure requirements over 4000psi, an additional booster operated with very low energy consumption can be used.
Main advantages of the system are:

Very low energy requirements due to cost-effective liquid compression
The DESY® 300/100 pumps exactly the quantity of nitrogen which is required by the user, even when strong fluctuations in demand occur
Unchangingly high quality of the injection moulded parts because of the very pure and oil-free nitrogen

Why is thermal metal spraying hazardous?

The high temperatures, velocity, and projectile distance of the spraying process create a unique set of health and safety hazards for the operator and those nearby.

Where is thermal metal spraying used?

Thermal metal spraying may be used to build up worn parts, apply a corrosion-resistant layer or to apply soldering or brazing filler metals. The process has found wide application in several industries, including:
?Aerospace / ?Machine shops / ?Power plants
?Agriculture / ?Marine / ?Pulp and paper
?Automotive / ?Medical / ?Steel mills
?Computers / ?Military / ?Textile
?Electronics / ?Oil and gas exploration and refining