Thermal Spraying
Thermal spraying processes (as classified in the EN 657 and ISO 14917 standards) offer a wide range of applications within modern surface technologies. Components made from a wide range of base materials can be coated with layers of high-melting-point metals or ceramics to protect them against wear and corrosion. Furthermore, thermally conductive or heat-insulating layers can be applied to highly thermally stressed components. Almost all coating materials that can be produced in powder or wire form can be processed in this way.
During thermal spraying, the coating materials are fed into — and melted by — an energetic heat source (fuel gas oxygen flames from combustible gas, arcs or plasmas of noble gases such as argon, hydrogen, nitrogen, helium). The particles, which are either softened or fully molten, are accelerated in the direction of the workpiece and collide with it at high speed (40–600 m/s). Once the heat has been transferred to the base material, the particles solidify and form a coating that consists of multiple layers. The desired thickness is achieved by repeated passes with the burner.

Base Materials Of Thermal Spraying
Almost any base material can be coated, including metals, ceramics, plastics, fiber composites or natural materials such as stone, wood, etc. Thermal spraying offers a great flexibility in terms of the possible material combinations.

Coating Thickness Of Coating
Achieving an optimal coating thickness — which may vary greatly depending on the application — is a prerequisite for good results. Depending on the material and process used, a coating thickness from a few tens of microns to several millimeters can be achieved. In the case of worn parts, for which the total thickness of the coating cannot be freely determined, the coating can be applied after a build-up layer.

Component Temperature During Coating
During the coating process, workpieces are usually heated to a maximum of 150°C and their surface temperature is monitored. Changes in the base material are largely excluded, with the exception of self-flowing alloys, which are subsequently fused at temperatures exceeding 1,000°C.

Pre-And Post-Processing From One Hand
To achieve the required surface quality, efficient finishing of the sprayed layers is just as important as selecting optimum materials of the necessary quality. For this reason, Nova Werke uses state-of-the-art facilities for turning, grinding, lapping, honing and polishing.

Quality Assurance For Materials, Equipment, Measuring Methods (Standards) And Personnel
Far from taking a "spray-and-pray" approach, our thermal spraying processes are based on consistent quality awareness on four M-levels: Material, Machine, Men and Measurement/Inspection. For comprehensive quality control, Nova Werke uses state-of-the-art test equipment for three-dimensional tolerance monitoring as well as a dedicated metallography lab, in which roughness measurements with track profile recording are carried out in addition to microsection analysis, hardness measurements and adhesion strength tests. These QA measures are coordinated with the customer on the basis of the applicable standards when the order is placed.

Thermal Spraying Processes At Nova Swiss:
Flame Spraying, Arc Spraying, High Velocity Flame Spraying (HVOF) And Plasma Spraying (APS)
The process to be used depends on the specific application. Economic considerations always play an important role here.
Gas temperature [°C] | Particle velocity [m/s] | Adhesive pull strength | Porosity [Vol.-%] | |
---|---|---|---|---|
Arc spraying | 4,000 | 100 | 10–15 | 10 |
Flame spraying | 3,100 | 40 | 10 | 10–15 |
High-velocity flame spraying | 3,100 | 800 | > 70 | 1-2 |
Plasma spraying | 15,000 | 200 | > 50 | 2–5 |
Coating Materials For Thermal Spraying And Their Features
Material Groups |
Material | Melting point [°C] |
Vickers Hardness [HV 0.3]* |
Typical Properties | Application Areas |
---|---|---|---|---|---|
Pure Metals |
Aluminum / Al | 660 | 80 | Soft | Corrosion protection for industrial and saltwater environments |
Copper / Cu | 1080 | 120 | Good thermal and electrical conductivity | Conductive layers, e.g. on non-conductors |
|
Molybdenum / Mo | 2600 | 700 | Good sliding and dry-running properties, hard, tough, good abrasion resistance, also suitable as corrosion protection. Extremely dense layers possible, good compressive strength | Sliding surfaces in general. Crankshafts, synchronizer and piston rings, pump parts, guides, diesel engine components, fit and press seats, prevention of fretting corrosion | |
Zinc / Zn | 420 | 30 | Low melting point, good corrosion protection | Corrosion protection such as aluminum (often also as an Al/Zn alloy), in particular for bridge and crane structures as well as containers, etc. | |
Tungsten / W | 3400 | 300 | High-melting-point element | Electrical contacts, electrodes |
Material Groups |
Material | Melting point [°C] |
Vickers Hardness [HV 0.3]* |
Typical Properties | Application Areas |
---|---|---|---|---|---|
Steel | Various alloys | 1325 – 1536 | 160 – 600 | Depending on the alloy: flexible to very hard, high fretting resistance, oxidation and acid-resistant | General repairs of heavily worn parts |
NiCr alloy | 1400 | 350 | Corrosion-resistant, very good adhesion, temperature-resistant. | Base and intermediate layers |
|
MCrAlY M = Ni, Co, Fe, |
1360 – 1410 | 400 – 500 | High melting point, corrosion-resistant | Base and adhesive layers | |
Stellite | up to 1400 | up to 700 | Corrosion-resistant, abrasion-resistant | General wear resistance, steam turbine components | |
Tribaloy (cobalt or nickel-based) |
up to 1600 | up to 650 | Wear and corrosion-resistant. Good hot hardness |
Resistant to fretting with good sliding properties |
Material Groups |
Material | Melting point [°C] |
Vickers Hardness [HV 0.3]* |
Typical Properties | Application Areas |
---|---|---|---|---|---|
Self-flowing alloys | NiCrBSi, NiCoBSi, CoCrNiMoBSi, CoCrNiWBSi |
1000 – 1100 | up to 800 | Hard, tough, dense, high abrasion resistance. Fusing possible. Good hot hardness |
General wear protection, especially for valve plating. Also used as corrosion protection. Fused layers are absolutely impervious |
Material Groups |
Material | Melting point [°C] |
Vickers Hardness [HV 0.3]* |
Typical Properties | Application Areas |
---|---|---|---|---|---|
Non-ferrous alloys |
Aluminum bronze | 1060 | 210 | Hard, tough, pressure-resistant, corrosion-resistant, good dry-running properties | Fretting protection with very good dry-running properties |
Nickel aluminum / NiAl | 1400 | 230 | Very dense with good adhesion and resistance to thermal shock and corrosion | Base or intermediate layers Bearing seats |
Material Groups |
Material | Melting point [°C] |
Vickers Hardness [HV 0.3]* |
Typical Properties | Application Areas |
---|---|---|---|---|---|
Ceramics | Aluminum oxide pure / Al2O3 | 2050 | up to 1000 | Very hard, abrasion-resistant, but relatively brittle, good electrical insulator | Textile machine components, electrical and thermal insulation, highly wear-resistant, e.g. for mixer blades |
Aluminum oxide + titanium dioxide /Al2O3 – TiO2 | 1900 | 850 | The titanium dioxide content improves the density, sliding properties and polishability, and also reduces the brittleness, however lower hardness values are achieved |
Mechanical seals, shaft protection sleeves, textile machine parts, hydraulic parts, pressure rollers | |
Chromium oxide / Cr2O3 | 2435 | 1200 | Excellent corrosion resistance, hard, highly abrasion-resistant, very dense, smooth layers | Pump parts, plungers, shaft protection sleeves, seal seats, textile machine parts | |
Zirconium dioxide / ZrO2 – Y2O3 stab. – MgO stab. – CaO stab. |
up to 2680 | up to 800 | Thermal insulation layer, poorly wettable with molten metal, electrically conductive at high temperatures | Casting machine components, molds, high-temperature nozzles, combustion chambers, high-temperature heating elements (>2,000°C) |
Material Groups |
Material | Melting point [°C] |
Vickers Hardness [HV 0.3]* |
Typical Properties | Application Areas |
---|---|---|---|---|---|
Cermets | Composite materials made from ceramics and metals or metal alloys |
These materials are usually a combination of two or more widely differing components. | Special applications and also suitable as intermediate layers |
||
Tungsten carbide + cobalt / WC-Co |
(up to 1500)* | 1450 | Hard, high fretting resistance, corrosion, erosion and thermal shock-resistant. Very dense layers, very good adhesion | General wear protection against abrasion and erosion | |
Tungsten carbide + cobalt-chromium / WC-CoCr |
(up to 1500)* | 1400 | For properties, see WC-Co coatings | Corrosion-resistant in aqueous solutions | |
Tungsten carbide + nickel / WC-Ni |
(up to 1500)* | 1450 | Like tungsten carbide, highly wear-resistant in corrosive media and at high temperatures | Chemical plant components, linings, hydraulic valves, machines and tool parts of all kinds. Ideal wear protection for aluminum components |
Material Groups |
Material | Melting point [°C] |
Vickers Hardness [HV 0.3]* |
Typical Properties | Application Areas |
---|---|---|---|---|---|
Pseudo alloys | Nickel graphite | (up to 1450)* | 44 | Self-lubricating thanks to free graphite | Plain bearings Also suitable for dry running (depending on the application) |
Ceramic metal Ceramic plastic Metal plastic |
- | - | No longer a homogeneous alloy, but often combines the properties of the two partner materials | Hard, abrasion protection (see "Cermets"), hard, non-wetting (foodstuffs/printing technology), e.g. Al-Si polyester run-in coating |
[ ]* The Vickers hardness values [HV 0.3] are guideline values for thermal spary coatings.
( )* Instead of the melting point, the sintering temperature for the composite materials is given here.
