High temperature friction and wear performance of TiB2-50Ni composite coating sprayed by HVOF technique

Abstract

The work aims to study the effect of temperature on friction and wear properties of TiB2-50 mass%Ni coatings. TiB2-50Ni ceramics-metal composite coatings were fabricated on 304 stainless steel substrate by high velocity oxygen flame spraying (HVOF) with “shell and core type” Ni coated TiB2 powder. Microstructure, element map distribution and phase structure of HVOF coatings were characterized by SEM, EDS and XRD, respectively. High temperature friction and wear properties of TiB2-50Ni composite coatings and 304 stainless steel substrates were systematically investigated. Porosity, thickness, average surface roughness, micro-hardness and bond strength of HVOF TiB2-50Ni coating are 2.3%, 300.8 μm, 2.3 μm, 766.1 HV and 22.6 MPa, respectively. Values of nano-indentation hardness (H), Young's modulus (Er), ratio of hardness to elastic modulus (H/Er), yield strength (H3/Er2) and elastic recovery (η) of HVOF coatings are all higher than those of 304 stainless steel matrix. The friction coefficient of 304 stainless steel substrate fluctuates greatly with wear rate being increased sharply during high temperature wear test. However, the friction coefficient of HVOF TiB2-50Ni coating without significant fluctuation from room temperature to 600 °C. The wear rate of HVOF coating at 600 °C is (2.73 ± 0.01) × 10−5 mm3/N·m, which is about a quarter of the wear rate of 304 stainless steel substrate of (11.07 ± 0.01) × 10−5 mm3/N·m. As friction temperatures increasing from room temperature to 150 °C, 300 °C, 450 °C and 600 °C, oxygen contents of worn surfaces of TiB2-50Ni coatings increased from 5.10 mass% to 10.88 mass%, 20.40 mass%, 31.21 mass% and 38.78 mass%, respectively. Abrasive wear, adhesion wear and oxidation wear are the main wear mechanisms of HVOF TiB2-50Ni coatings during high temperature friction test. Comparing to 304 stainless steel matrix, TiB2-50Ni composite coating has more superior high temperature friction and wear properties.