Pre-, intermediate, and post-treatment of hard coatings to improve their performance for forming and cutting tools

Three coating systems, including single-layer AlCrSiN coatings, two-layer CrSiBN/CrN coatings, and single-layer TiAlN coatings were deposited using an arc evaporation system. The effects of various pre-, intermediate, and post-treatments on the properties and performance of the coatings were studied. The tribological properties of the AlCrSiN and TiAlN coatings were evaluated using ball-on-disc tests. The wear behavior of the AlCrSiN coatings was affected by coating morphology. The wear volume of the counter surface increased with the surface roughness of the coating. Furthermore, material transfer and build up to the coating surface were higher for the surfaces treated by grinding and shot blasting than those treated by other methods. The erosion and corrosion properties of the CrSiBN/CrN coatings were evaluated in molten aluminum and sulfuric acid, respectively. Intermediate treatment of the CrSiBN/CrN coatings improved their erosion and corrosion resistance by preventing formation of localized erosion and corrosion. Post-treatment of the TiAlN coatings decreased the amount of material transfer and wear volume of the counter surface. Meanwhile, drilling tests of the TiAlN coatings showed that post-treatment of the coatings improved the drilling regularity and stabilized the spindle torque, which helped to improve tool wear and cutting performance. Based on these results, mechanical surface pre-treatment by processes like micro-blasting, polishing, and buffing, along with plasma nitriding can improve the tribological properties and adhesion of coating systems. Likewise, intermediate and post-treatment of coating surfaces improve erosion and corrosion resistance and cutting performance. In conclusion, the studied treatment processes gave coatings with good performance that are possible candidates for forming and cutting tools.