Research On The Preparation And Tribological Properties Of WC-reinforced W-Cu-Ni-based Composites

The guide plate is an important part of the guide device in the steel rolling production line,which requires high-temperature wear resistance and high-temperature fatigue resistance.However,it is difficult for the existing materials to fully meet the requirements.In this dissertation,the copper-coated tungsten composite powder was prepared by electroless plating.The W-Cu-Ni-WC composite materials were successfully prepared by the vacuum hot-pressing sintering process with the hard phase and the copper-coated tungsten composite powder.The friction and wear behaviors were investigated in order to meet the using requirements of guide plates and liners.The main research contents and conclusions are as follows:The copper-coated tungsten composite powder with a good surface structure was successfully prepared by the electroless plating.The copper coating had a hilly morphology with a dense structure.The surface of the coating was deposited by fine metal spherical particles.The phase of composite powder contained W and Cu,and might also contain Cu_0.4W_0.6.When the sintering temperature was 950℃,the sintering pressure was 40 MPa,the holding time was 2 h,the Cu content in the composite powder was 20 wt.%and the amount of WC particles added was 1.5 wt.%,the W-Cu-Ni-WC composite had the highest density（97.3%）with the Vickers hardness of 245.00 HV which was 44.1%higher than the 70W-Cu-Ni composite.In the vacuum environment,compared with the wear rate of 70W-Cu-Ni composite materials,the wear rates of 70W-Cu-Ni-1.5WC composite materials were reduced by 35.2%,67.7%,2.8%,47.9%and 17.6%,respectively at 25℃,300℃,500℃,700℃and 900℃.Both composite materials had good low friction.As the temperature increased（25℃～900℃）,the wear rate of the 70W-Cu-Ni-1.5WC composite materials gradually increased(1.99×10^-5～6.64×10^-4mm³·N^-1·m^-1),and the friction coefficient had the minimum and maximum values at 700℃and900℃（0.197 and 0.348,respectively）.The oxidation products on the wear surfaces of the two composite materials were mainly WO₃and WO₂at 700℃and 900℃.The wear mechanisms were abrasive wear,adhesive wear,fatigue wear and oxidative wear.As the temperature changing,the dominant wear mechanism changed accordingly.In the nitrogen environment,the friction coefficient of 70W-Cu-Ni-1.5WC composite materials fluctuated between 0.235 and 0.368 with the increasing temperature,the wear rate(7.6×10^-5～3.59×10^-3mm³·N^-1·m^-1)gradually increased with the increasing temperature（25℃to 700℃）.At 25℃～500℃,the wear mechanisms were mainly abrasive wear and adhesive wear,supplemented by fatigue wear.At 700℃,the wear mechanisms were mainly abrasive wear,supplemented by adhesive wear,fatigue wear and oxidative wear.At 900℃,the wear rate dropped to4.5×10^-4mm³·N^-1·m^-1because the wear mechanism had changed to abrasive wear and fatigue wear with supplemented adhesive wear and oxidative wear.The oxidation products were WO₂and WO₃.In the argon environment,as the temperature increased（25℃～900℃）,the friction coefficient of 70W-Cu-Ni-1.5WC composite materials fluctuated between0.269 and 0.350,which had the minimum and maximum values at 25℃and 500℃（0.269 and 0.350,respectively）.The wear rate of 70W-Cu-Ni-1.5WC composite materials gradually increased(5.32×10^-5～3.23×10^-3mm³·N^-1·m^-1).At 25℃,the wear mechanisms were mainly abrasive wear and adhesive wear,supplemented by fatigue wear.At 300℃,the wear mechanisms were mainly fatigue wear and adhesive wear,and abrasive wear was supplemented.At 500℃,the wear mechanisms was mainly adhesive wear,supplemented by fatigue wear and abrasive wear.At 700℃,the oxidation products were mainly WO₂and WO₃on the wear surface,the wear mechanisms were mainly fatigue wear and adhesive wear,the abrasive wear and oxidative wear were supplemented.At 900℃,the oxidation product was mainly WO₂on the worn surface,the wear mechanisms were mainly abrasive wear,adhesive wear and fatigue wear,supplemented by oxidative wear.The mechanical mixed friction layers were the most important wear morphologies on the worn surface,and the repeated cyclic deformation was the main form in the wear failure of the70W-Cu-Ni-1.5WC composite in argon at different temperatures.