Enhancement of wear and mechanical properties of thermally sprayed WC-Co coatings by HI Ping post-treatment

摘要

The aim of this investigation was to ascertain the beneficial improvements in tribo-mechanical properties of post-treated thermal spray WC-Co coatings. Thermally sprayed WC-Co coatings which are deposited by the high velocity oxy-fuel (HVOF) process are well known for their excellent wear resistance, and are widely used as machine parts. However, there is an ever-increasing demand to produce coatings which have even higher wear resistance and mechanical strength. One possible method to satisfy these requirements is the hot isostatic pressing (HIPing) post-treatment of thermally sprayed WC-Co coating substrate system. However, the application of HIPing process to WC-Co coating on steel substrates is not easy because of big differences in thermal expansion coefficient between the two materials. In this study, rather low HIPing temperatures (850 ～ 1000°C) and high pressure (150 MPa) were employed. As a result, it was possible to get the hardness of the coating equal to hot pressed WC-Co material. Consequently, due to the improved hardness and other microstructural improvements after the HIPing post-treatment, the wear loss of HIPed coatings reduced to almost half of the as-sprayed WC-Co coatings.