Tribological investigation of HVOF sprayed Ni-based coatings on SS 316L in water-cooled nuclear reactor

Abstract

The sodium and water-cooled nuclear reactors play a significant role in energy producing sectors. However, the maintenance of these reactors is more challenging. A 316L austenitic stainless steel are a major construction material used in nuclear reactors due to its high corrosion resistance. However, these components are subjected to wear due to its low hardness. The cobalt-based coatings were employed in some reactors for improving the wear properties. However, it has been observed that these coatings lead to the formation of Co-60 isotopes in the reactor and emits gamma rays, which are harmful to the maintenance personnel. Nickel based coating can be used as a substitute to the Co-based coating on SS 316L to avoid the risk involved. This paper presents the characterization of the HVOF sprayed Ni-based coating over SS 316L substrate and the wear and friction behavior of SS 316L and coating against silicon nitride at nuclear environment condition. The coating properties were obtained and presented. The friction and unidirectional sliding wear tests have been carried out using a pin on disc tribometer. The estimated mass wear rate for the coating has been found as 4.15 × 10-5g/Nm. The coating offers high wear resistance as compared to SS 316L material and hence recommended for the components of the water-cooled nuclear reactor.