Using an acetylene-oxygen flame at a temperature of approx. 3000-3200°C, the spray material in powder form is accurately metered, melted and atomized. Followed by a heat treatment at about 1050-1150ºC, where the fusing takes place.
The aim of fusing is to obtain optimal adhesion between the individual spray particles, the top layer and the substrate. The result is a metallurgical compound with a diffusion zone of several tens of microns. The typical characteristic microporous lamellar structure of the cold spray process is no longer present. With autogenous powderspray the coatings have a homogeneous structure. These hot sprayed layers are well resistant to line, point and impact loads.
Features of autogenous powderspray coatings
- Microporous lamellar structure
- Relatively high degree of oxidation in the coating
- Moderate tensile strength
- Good compressive strength
- Low stretch properties
- Versatile and a choice of many materials
Materials autogenous powderspraying
Materials such as the so-called self-smoothing alloys or carbides. These hardfacing materials are comparable to stellites and welded carbides. The layers are made on the basis of Nickel, Chrome or Cobalt. Optionally with additives of tungsten carbides. The hardness ranges from Rc 30 to Rc 75.
- Melting alloys NiCrBSi (Fuses, Fusing, Self-fluxing)
- Nickel based alloys
- Various stainless steel alloys
- Cermets, carbides
- Ceramic coatings (oxides)
- Easy wearing coatings (abradables such as Nickel graphite, AlSi-polyester )
Applications of autogenous powderspraying
Against running into the seals.
To improve abrasion resistance and chemical protection.
Boiler walls or incinerators
Against high temperature erosion and chemical degradation.
Repairs or size corrections
From run-in journal or bearing seats with nickel-based alloys.
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More flame spray
Flame spray is a unique and practical technique to apply a coating to almost any kind of metal and non-metal surfaces. This coating improves the basic material properties such as hardness, abrasion, scratch and corrosion resistance.
HVOF flamespray forms a coating with a high density and a high bonding value. The HVOF flamespray principle is based on a transfer of thermal and, in particular, kinetic energy from the spray particles of the substrate.
The high heat level and conductivity of the plasma flame, in combination with the very high gas- and transport velocity of the molten particles result in optimal condtions for very strong adhesion, uniformity and purity of the sprayed layer.
Electric wire spraying is a form of thermal spraying where two consumable metal wires are fed independently into the spray gun. With electrical wire spraying, coatings can be applied quickly and at low cost.
For corrosion protection, repairs or size corrections. The spray layers applied in this way are more or less impact or shock resistant. The structure of the layer is always micro-porous. This gives the ability to hold oil and thus self-lubricating properties are obtained.