Structure And Properties Of Reactive Magnetron Sputtering Al-Cu-N Coating

Doping soft metallic phase into hard phase (nitride, carbide, boride) to form nanocomposite coating is a very important way to improve properties of hard coatings. With metallic doping refinement, propertities including the hardness, toughness, wear resistance, and corrosion resistance could be improved. The A1-Cu-N coating composing of hard AIN phase and soft Cu phase is a typical sample.In this work, the A1-Cu-N nanocomposite coatings with various Cu content (0-25.4at.%) were depositied by two targets reactive magnetron sputtering. The energy-dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS) were used to analyze chemical composition, phase structure, microstructure and and chemical states, respectively. The nanoindentation was used to test the mechnical properties, such as hardness, modulus, and elastic recovery. The indentation test was carried out to analyze the toughness. Overmore, the tribology test was used to analyze the tribology propertity, wear rate and friction coffencient. The main results are shown as following:1. The growth structure evolved from columnar and porous (0-1.7at.%Cu), through column-free and dense (7.3-17.7at.%Cu), to column-free yet porous (25.4at.%Cu). In a wide range of7.3-17.7at.%Cu content, a dense growth structure could be obtained. It is also a grain size refinement processing, the AIN grain size decreases from around35nm to about10nm. For the coating with11.5at.%Cu, the copper phase appeared to exist as isolated globular grains within a hard AIN matrix.2. There is only Cu-Cu bond in1.7at.%Cu coating, the Cu-Al bond could be seen in the coatings with7.3-25.4at.%Cu, also, the Cu-A1percentage rises first and then retains at about25%. The Cu-A1bonding mainly came from the interfacial interaction between the constituent AIN and Cu phases.3. The Cu content affects the mechanical properties, the hardness gradually increases with the increase of Cu content, then decreases due to too much Cu. In the range of7.3-17.7at.%Cu content, the value of hardness retains at a high level 25-40GPa, also with a high elastic recovery R>78%, and high H/E*ratio≥0.1. The maximium harness is40GPa for the coating with11.5at.%Cu. For the coating with17.7at.%Cu, H=27.3GPa, E*=273.8GPa, which shows a good resistance to cracks, the critical load without crack is5N. Moreover, there is also a relationship between R and H/E*ratio, two groups could be divided, Group I (R>78%, H/E*≥0.1) and Group Ⅱ(R<78%, H/E*<0.1).4. For dense coatings with11.5at.%and17.7at.%Cu, at the condition of2N-1000m, the cofficient of friction is0.95±0.05, which is lower and steadilier than M42substrate and the wear rate K<5x10-16m3/Nm. For17.7at.%Cu coating, K=1.3x10-16m3/Nm, which decreases more than60%than M42substrate.