Wear Behavior of a Borided Nickel-Based Self-Fluxing Thermal Spray Coating

Abstract

Increasing the hardness of materials used in machines can lead to a longer useful life while decreasing maintenance downtime. However, high hardness usually results in an increase in brittleness of the material, which can be avoided by surface treatments, such as thermal spray coatings that are largely used to produce coatings with high resistance to wear and corrosion. This method has advantages, such as easy application, relatively inexpensive in comparison with other methods, and does not increase the brittleness of the base material. However, in some applications, the wear resistance may not be sufficient. To further improve the wear resistance of these coatings, a thermochemical boriding treatment can be subsequently applied to produce a duplex coating. In this work, an SAE 1020 steel was used as the substrate for the application of a thermal sprayed surface coating. The alloy applied is nickel based and self-fluxing with composition NiCrBSiC. The boriding treatment was subsequently performed at 850°C for 2 h. Optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Vickers micro-hardness and micro-abrasive wear tests were used to characterize the samples. The flame spray produced coatings of approximately 900 HV, which was increased to 1600 HV after the boriding treatment.