Adhesion Strength of HVOF Sprayed IN718 Coatings

Abstract

The adhesion strength of high-velocity oxyfuel thermally sprayed coatings is of prime importance when thick coatings are to be sprayed in repair applications. In this study, relationships between process parameters, particle in-flight characteristics, residual stresses, and adhesion strength were explored. The most important process parameters that influence HVOF sprayed IN718 coating adhesion strength on IN718 substrate material were identified. Residual stress distributions were determined using the modified layer removal method, and adhesion strength was measured using an in-house-developed tensile test. Relationships between process parameters, particle in-flight characteristics, coating microstructure, and adhesion strength were established. Particle temperature, particle velocity, substrate preparation, and deposition temperature were identified as critical parameters to attain high adhesion strength. Controlling these parameters can significantly improve the adhesion strength, thus enabling thick coatings to be sprayed for repair applications.

Deposition and characterization of high velocity oxy‐fuel sprayed nickel chrome boron silicium based coatings on stainless steel substrates

“…Whereas, with the increase in spray distance, the inflight residence time also increases with an increase in particle velocity which produces a better interlocking of molten powder particles with steel substrate causing an increase in the adhesion strength. A similar variation in the adhesion strength for high-velocity oxy-fuel sprayed inconel 718 has been observed [26]. With further increase in spray distance above that value the molten particles start vaporizing and break down into fragments due to the high in-flight time.…”

Cold Spray: Over 30 Years of Development Toward a Hot Future

“…Coatings to be used in harsh environments and with high mechanical properties at elevated temperatures are of great importance for the advancement of power generation technologies, such as in pressure tubes in thermal and nuclear power plants, in chemical factories, in the oil gas generation industry, and inside boilers where waste and biomass are used (Ref 331 ). Cost effective and thick coatings of nickel-based superalloys (Ref 332 , 333 ), steel and stainless steel alloys (Ref 334 - 336 ), titanium alloys (Ref 337 , 338 ), tantalum (Ref 339 , 340 ), and niobium (Ref 341 , 342 ) have been produced using several thermal spray processes, such as HVOF, HVAF, APS,WAS, and TWAS (Ref 333 , 334 , 336 , 337 , 343 , 344 ). They are usually characterized by a high-oxide content (Ref 334 , 336 , 339 , 345 ), high porosity levels (Ref 334 , 337 , 340 , 344 - 346 ), and micro-cracks (Ref 343 , 345 , 346 ).…”

Experimental evaluation of interfacial adhesion strength of cold sprayed Ti-6Al-4V thick coatings using an adhesive-free test method

“…For example, CS coated Cu on 316L, Cu, and Al alloy substrates [33,34], CS coated Al-Al2O3 on Al7075 [35], CS coated CP-Ti on mild steel substrate [36], and HVOF sprayed IN718 on IN718 [37].…”