Experimental Investigation of Single Shot Peening on TiN Coated surfaces

Improvement of the mechanical properties of the coated surfaces was the matter of significant researches for a long time. A lot of physical and chemical operations were applied and examined on the coating surfaces successfully, but the effect of the mechanical treatments was not widely investigated. In this paper, the effect of a surface mechanical treatment on the micro coating layer has been studied and investigated. For this purpose, the necessary conditions have been created for implying impact to the coating surface. A setup of gas gun facility with well-designed and prepared projectiles are used to strike the sample surface with different speeds. A significant number of impacts­ have been inflicted on the test sample of the spade drill insert cutting tool. The consequence of this process is the change in crystal structure of the coating layer, which shows that under the created conditions, the crystal structure was not destroyed and­ instead getting compacted so that the size of the crystal grains has been reduced and considerably refined. ­Subsequent studies using electron microscopy have led to the measurement­ of the average size­ of the crystalline grains before and after impacts. Obviously, a significant effect has been observed and a meaningful trend has been seen for this change in the form of a linear relationship. The main result is that about ۴% reduction in the average grain size happens when the impact speed changes by ۱۰m/s. In this way, the principal basis for the use of this surface treatment in improving the surface properties of the micro coating layers is provided. This leads to the application of such treatments as an industry process for improvement of thin coating mechanical properties.

کلیدواژه ها:

Surface mechanical treatment ، titanium-based coatings ، grain refinement ، improving coating surface properties ، mechanical impact treatments