Ni기 자융성합금 코팅층의 마모거동

Abstract

Recently, it is required that high performance of wear resistance, corrosion resistance and thermal resistance of the materials used in machinery, automobile and aerospace industry. Especially, it is surface of the material that meet with outside environment, many studies about surface modification that give excellent mechanical properties such as wear resistance, corrosion resistance and thermal resistance to surface of the materials are actively performed. One of those techniques, the high-strength Ni-based alloy coating by thermal spray process is applied widely in many industrial areas. Thermal spray process has some advantages such as relatively simple process and low cost of operation but it has defects too, such as low adhesive strength with substrate and existing the pore inside of coating layer. Ni-based self-flux alloy has been developed to remedy such limitations. It includes a fusing process after thermal spray to improve adhesive strength and to remove pores from coating layers. It is known that the Ni-based self-flux alloy coating layer with heat treatment has high hardness and excellent wear resistance. This study aims at investigating the effects of heat treatment conditions on the microstructure, mechanical properties and dry sliding wear behavior and effects of sliding speed and applied load on the dry sliding wear behavior of heat treated at 1000℃ thermally sprayed Ni-base self-flux alloy coating fabricated by flame spray process. First, Ni-base self-flux alloy powders were flame-sprayed onto a carbon steel substrate and then heat-treated at 700, 800, 900 and 1000℃. Their microstructure and hardness were researched and dry sliding wear tests were performed. And then investigated about the effect of sliding speed and applied load on the dry sliding wear behavior of thermally sprayed Ni-base self-flux alloy coating which heat treated at 1000℃. Dry sliding wear tests were performed using sliding speeds of 0.2, 0.4, 0.6 and 0.8 m/s and the applied loads of 5, 10, 15 and 20 N. Wear behavior of Ni-based self-flux alloy coatings which heat treated at 1000℃ was observed and analyzed. The main results obtained are as follows; 1) After heat treatment, pores and boundaries in coating layer are decrease with heat treatment temperature increasing. Especially, treat temperature at 1000℃, The coating layer remolded and recrystallized. 2) According to increase of heat treatment temperature, the hardness does not changed greatly. But distribution of hardness decreases with increasing temperatures. 3) According to increase of heat treatment temperature, splat delamination decrease. And wear behavior is transferred from delamination to abrasion wear. This transfer of wear behavior is reason of increasing of wear resistance with heat treatment temperature increasing. 4) At a constant sliding speed, as applied load increases, the wear behavior transfer from abrasive to adhesive. Also, as applied load increases, adhered lump through adhesive wear increases, thus increasing the wear rate. 5) At a constant applied load, the increase in wear rate causes early transition from abrasive to adhesive so that a layer is formed through adhesive wear, thus decreasing the wear rate.