Effect of mechanical properties of CrN/CrCN coatings and uncoated 1.402 stainless steel on the evolution of degradation and surface roughness in cavitation erosion

The effect of the mechanical properties of CrN/CrCN multilayer ceramic coatings on cavitation degradation and surface roughness was investigated. Three coatings with comparable thickness and modulus but the different thicknesses of the CrCN layer, and uncoated 1.402 steel were tested. Increasing the thickness of the CrCN layer increased hardness (H) and Young's modulus (E), but decreased the LC1 force at which the first cracks appear. No correlations were found with LC2 force, at which coating is completely removed. The H3/E2 ratio of better correlated with erosion rate and eroded area than the ratio of H/E. The eroded area of CrN/CrCN coatings was related to the erosion rate. For the H3/E2 ratio bigger than 0.1 GPa, the erosion rate increased with increasing this parameter. The failure mechanism influenced the nature of the relationship between roughness and volume loss in cavitation erosion studies. In the case of systems with hard and rigid coatings, the increase in surface roughness was accompanied by a decrease in volume loss. Changing the degradation mechanism during the tests leads to a loss of correlation between roughness and erosion rate.

Automated summary

The mechanical properties of CrN/CrCN multilayer ceramic coatings have been found to affect cavitation degradation and surface roughness. Increasing the thickness of the CrCN layer improves the hardness and Young's modulus of the coatings, but decreases the force at which cracks appear. The H3/E2 ratio is a better indicator of erosion rate and eroded area than the H/E ratio. Surface roughness and erosion rate may not have a consistent correlation due to the influence of degradation mechanisms.