Research Areas

Detonation Spray Coating Technology

D. Srinivasa Rao, G. Siva Kumar, D. Sen

DSC is a unique variant in the family of versatile thermal spraying which contributes reputation among the exhaust surface modification technologies. The development of Detonation spray coating technology at ARCI is aimed to transfer the total technology, along with equipment and know-how of the coating process to the Indian entrepreneurs and also to the other countries.

Process: A method of coating, where an explosive high temperature flux of gas mixtures is used as a source for heating, accelerating and spraying the particles

Salient Features

	Excellent Adhesion		Low Oxide Content
	< 1% Porosity		Good Tribological Properties
	High Microhardness		High Coating Thickness
	Low Thermal Degradation		Good Powder Efficiency

Advantages

	Low Substrate Temperature		Less Electrical Consumption
	Low Cost of Operation		Less Down Time
	Less Gas Consumption		Less Work Scrap
	Less Water Consumption

Process Capabilities

	Thickness Buildup: 5-25 μm/shot		Particle Velocity: 500 to 1000 m/s
	Coating Thickness		Particle Temperature: up to 4000oC
	Carbides/Cermets: 20-500 μm		Deposition Efficiency: 30 to 60%
	Ceramics: 50-1,000 μm		Porosity: 0.1 to 1.0%
	Metals & Alloys: up to few mm		Bond strength: >75 MPa
	Coating Coverage: 0.5 to 1.0 m2/hr		Coating hardness: WC-Co-1,300 HvCr3 C2-NiCr-1,000 Hv

Type of Powders Sprayed

Metals, Oxides & Cermets, Carbides and Alloys

Substrate Materials

Metals, Alloys, Superalloys, Dielectric substrates, Plastics, Glass and Ceramics (Any substrate having hardness < 65 HRC can be coated by DSC)

Examples of Powders Sprayed

Al2O3, Al2O3-TiO2, Cr3C2-NiCr, WC-Co, WC-Co-Cr, WC-17Co-8FEP, WC-10.5Co, WC-10.5Ni, Ni-20Cr, CoCrAlY & NiCrAlY, SS316-Martensitic, Austenitic, Cr2O3, Aluminum bronze, NiCr-5Al, Stellite-6, Cr2O3-20 Al2O3, Ti(C,N)-38%(Ni, Co), Ti(C,N)- 38%(Ni, Co, Mo), Fly ash, AlN (from SHS), Fe-Al (with Al2O3, Cr2O3), Cr3C2-NiCr- TiB2, Fe-SiC, Al65Fe20Cu15, Fe, Ni, Cu and many pure metals.

DSC vs APS

	Higher bond strength (> 10000 psi)		Controlled residual compressive stress
	Denser microstructure (< 1% porosity)		Very thick coatings can be produced without delamination
	Reduced thermal degradation		Very high melting point materials like Zirconia can not be sprayed
	Smoother as-coated surface finish (1-4μm Ra)

DSC vs HVOF

	Coating properties nearly similar		HVOF has higher productivity
	HVOF CANNOT SPRAY OXIDES		DSC operating costs are much lower
	DSC fully indigenous – spares/servicing issues much simpler