Abstract
The aim of this experimental study was to comprehend the relative performance and failure modes of WC-NiCrBSi Thermal Spray coatings in As–Sprayed and HIPed (Hot Isostatically Pressed) conditions in rolling/sliding contact. Recently a number of scientific studies have addressed the fatigue performance and durability of Thermal spray coatings in rolling/sliding contact, but as of yet there have been no investigations on Thermal Spray Coatings which have undergone the post treatment HIPing. The understanding of the mechanisms of failure in rolling /sliding contact after HIPing is therefore critical in optimising the parameters associated with this post treatment to achieve superior performance. Coatings were deposited by a JP5000 system and HIPing was carried out at two different furnace temperatures of 1123K and 1473K. At both HIPing temperatures the rate of cooling was kept constant at 8°C/minute. Rolling Contact Fatigue tests were conducted using a modified four ball machine under various tribological conditions of contact stress, configuration and lubrication. Results are discussed in terms of as-sprayed and HIPed surface examination of rolling elements using Scanning Electron Microscope (SEM) and Light Microscope.
