Structure and properties of lanthanum doped AlCrN coatings

AlCr(La)N coatings were grown through mid-frequency reactive magnetron sputtering on cemented carbide (YG8) and single-crystal silicon (111) wafer. The composition, microstructure and mechanical properties of the coatings deposited under different La target currents were evaluated. The concentration of La changed from 0 at.% to 7.73 at.% displaying a low rate of back-scattering compared to Al and Cr. La partly acted as a partial solid solution in the AlCrN lattice, whereas an increased amount of La was likely to be intergranular gathered, resulting in segregation at the grain boundaries and a grain size decrease. During this phenomenon, nc-AlCrLaN crystalline grains combined with a-La2O3/a-LaN were formed. The multilayer morphology appeared as the La target current increased. The friction coefficient of the AlCrLaN coating decreased due to the solid lubrication of La2O3. The AlCrLaN coating under the La target current of 1 A (La concentration 1.39 at.%) obtained the highest H/E ratio, H3/E⁎2 ratio, abrasive resistance and adhesion strength.