Mechanical and microstructural properties of NiCrFeSiBC/Cr₃C₂ composite coatings – part I

Abstract

NiCrFeSiBC/Cr₃C₂ composite coatings were developed on to GrA1 boiler steel by high velocity oxy fuel spray process. The aim was to develop the novel composite coating by finding optimum concentration of Cr₃C₂ in NiCrFeSiBC matrix, which further possesses the superior solid particle erosion resistance. The mechanical and microstructural properties of the developed coatings were critically examined. The as sprayed coatings were characterised by X-ray diffraction, SEM/energy dispersive spectroscopy analyses. The coatings exhibited characteristic splat-like morphology with the presence of micropores, unmelted and semimelted particles and inclusions. The adhesion strength of the developed coatings was also determined. The physical properties like surface roughness, porosity and microhardness of the as sprayed coatings have also been reported. The blending resulted into the formation of composite-like coatings where, the Cr₃C₂ phase was nearly uniformly distributed into the NiCrFeSiBC matrix. The results have been discussed with respect to the existing literature.

Keywords:

• Boiler steels
• Coatings
• Microsturcture
• HVOF spray
• NiCrFeSiBC coating
• Cr₃C₂

Acknowledgements

The authors would like to thank the Deen Bandhu Chhotu Ram Thermal Power Plant located at Yamuna Nagar in Haryana (India) for providing the boiler steel material. The authors wish to thank MECPL Jodhpur (India) for development of HVOF thermal spray coatings on the selected boiler steel material. Moreover, the authors owe special thanks to Dr H. Singh for extending the necessary facilities and support in conducting the detailed analysis at Indian Institute of Technology Ropar, Roopnagar, Punjab, and Dr S. Parkash at Indian Institute of Technology Roorkee, Roorkee.