플라즈마 용사로 제작한 세라믹 코팅 층의 마모 특성

Abstract

This study is to investigate the wear behaviors of four types of ceramics, Al₂O₃, TiO₂, Cr₂O₃ and ZrO₂, coated by plasma thermal spray method under lubricative environments. The lubricative environments are grease and bearing oil. The wear testing machine used a pin on disk type. Wear characteristics, which were friction force, friction coefficient, wear rate and friction power, according to the lubricative environments were obtained at the four kinds of load, and the sliding velocity, 0.1m/s and 0.2m/s. After the wear experiments, the wear surfaces of the each test specimen were observed by a scanning electronic microscope. The obtained results are as follows. 1. On dry frictional condition in air, the friction coefficient, the sliding velocity of 0.1 m/s with low load, was the least in TiO₂ and the greatest in ZrO₂. In this case, the coefficient ordering is TiO₂ < Al₂O₃ < Cr₂O₃ < ZrO₂, but the coefficient ordering high loads at is TiO₂ < Cr₂O₃ < Al₂O₃ < ZrO₂. At the sliding velocity of 0.2 m/s with low load, the coefficient ordering is Cr₂O₃ < TiO₂ < Al₂O₃ < ZrO₂, but coefficient ordering at high load is TiO₂ < Cr₂O₃ < Al₂O₃ < ZrO₂. Therefore, the friction coefficient at 0.2 m/s is less than that at 0.1 m/s. 2. On wear behaviour of Al₂O₃ under lubricative environment, The friction coefficient under grease, the sliding velocity of 0.1m/s with the load of 300N, was in a range of 0.08 ~ 0.17 and 0.09 ~ 0.12 under bearing oil. And the friction coefficient, the sliding velocity of 0.2 m/s with 900N, was in a range of 0.08 ~ 1.12 under grease and 0.05 ~ 0.07 under bearing oil. Therefore, when the sliding velocity is faster and the loading gets heavier, the bearing oil shows more tribology characteristics than that of grease. 3. On wear behaviour of TiO₂ under lubrication environment, The friction coefficient under grease, the sliding velocity of 0.1m/s with the load 300N, was in a range 0.17 ~ 0.27 and 0.12 ~ 0.21 under bearing oil. And the friction coefficients at the load 900N were approximately 0.14 and 0.11 under bearing oil. The friction coefficient, the sliding velocity of 0.2m/s with the load of 300N, was in a range of 0.07 ~ 0.18 under grease and 0.13 ~ 0.18 under bearing oil. And the friction coefficient, the sliding velocity of 0.2 m/s with 900N, was in the range of 0.12 ~ 0.14 under grease and 0.07 ~ 0.09 under bearing oil. 4. On wear behaviour of Cr₂O₃ under lubricative environment, The friction coefficient the velocity of 0.1 m/s with the load 300N, was in a range of 0.17 ~ 0.26 and under grease 0.13 ~ 0.17 under bearing oil. And the coefficient at the load 900N was in a range of 0.11 ~ 0.12 under grease and 0.11 ~ 0.13 under bearing oil. At the sliding velocity of 0.2m/s at the load of 300N, the friction coefficient was in a range of 0.06 ~ 0.14 under grease and 0.12 ~ 0.16 under bearing oil. At load 900N, the value was in a range of 0.09 ~ 0.11 under grease and 0.13 ~ 0.15 under bearing oil. Therefore, when the sliding velocity is faster, the bearing oil is better tribology characteristics than grease. 5. On wear behaviour of ZrO₂ under lubricative environment, At the velocity of 0.1 m/s and the load 300N the friction coefficient was 0.21 under grease and 0.18 under bearing oil. At sliding velocity 0.2m/s and load 500N, the friction coefficient was in a range of 0.12 ~ 0.16 under grease and 0.08 under bearing oil. The bearing oil is more suitable than grease for lubrication. 6. On the wear rate of 4 ceramics, the rates with load 300N in air were 1.290×10-7 for Al₂O₃, 1.72×10-8 for TiO₂, 3.97×10-7 for Cr₂O₃ and 1.993×10-6 for ZrO₂, respectively. The rates with 900N in grease were 2.16×10-9 for Al₂O₃, 1.00×10-9 for TiO₂, 3.90×10-9 for Cr₂O₃ and 6.91×10-6 for ZrO₂. And, the rates with 900N in bearing oil were 5.22×10-9 for Al₂O₃, 1.40×10-9 for TiO₂, 1.00×10-9 for Cr₂O₃and 9.11×10-8 for ZrO₂, respectively. Therefore, the wear rate under grease is the least for TiO₂ and the greatest for ZrO₂ and the rate under bearing oil is the least for Cr₂O₃ and the greatest for ZrO₂. 7. Frictional power of Al₂O₃, is 9.42Nm/s when load is 100N in the dry friction and 18.27Nm/s when load is 200N. If load is increased, frictional power shapely go up. In the case of TiO₂, although load is increased, frictional power is not increased because of adhesive effect. In case of Cr₂O₃, friction power in the air is 13.20Nm/s with 100N, 21.27Nm/s with 200N, and 22.81Nm/s with 300N. The friction power of ZrO₂ is mild adhesive wear in low load and slowly increased because of low fracture toughness. 8. The wear mechanisms were abrasive wear for Al₂O₃, adhesive wear for TiO₂, adhesive wear for Cr₂O₃ and delamination wear and mild abrasive wear for ZrO₂.