Stress evolution in CrN/Cr coating systems during thermal straining

Cr-N, Cr and CrN/Cr coatings were deposited at 350 degrees C on monocrystalline Si(100) and polycrystalline austenitic stainless steel substrates by magnetron sputtering using Cr targets in Ar + N-2 atmosphere. The stress evolution in the coating systems were characterized using X-ray diffraction and wafer curvature technique in the temperature range of 25-550 degrees C. Both techniques revealed larger stresses in coatings deposited on the steel substrates. The heat treatment reduces the deposition point defect concentration, which is reflected in a decrease of intrinsic stresses in Cr and CrN coatings. Additionally, roughness of the Cr films decreases. The stresses in the individual sublayers of the CrN/Cr bilayer coatings indicate that the constraint imparted by the CrN layer on the buried Cr layer prevents a stress relaxation in Cr since no stress hysteresis is observed during, heating and cooling. The intrinsic stresses of CrN are - 3.4 * 10(9)Pa on the steel substrate and - 1.7 * 10(9)Pa on the Si(100) substrate. For Cr intrinsic stresses of - 1.35 * 10(9)Pa are obtained on steel and - 0.7 * 10(9)Pa on Si(100). The intrinsic stresses of CrN in the CrN/Cr bilayer system remains at - 3.4 * 10(9)Pa on the steel but increases to - 2.8 * 10(9)Pa on the Si(100) substrate. As a result of the annealing cycle, a stress relaxation of approximately 1.3 * 10(9)Pa is obtained for CrN on steel but 3.4 * 10(9)Pa are relaxed for CrN in the CrN/Cr/steel system. (C) 2007 Elsevier B.V. All rights reserved.