15secs.
When 5mN load is applied for 15secs onto the WC-Co having a thickness of 750nm it will resist upto certain extent but due to the difference in the modulus of Film and substrate .Tensile stresses aroused at the interface of the coating and the substrate and interfacial crack can be seen .When we apply load whole of it is taken by the coating itself and no plastic deformation or small of the substrate can be seen.and also as we see the H3/Er2 ratio the ratio will be higher for the WC-Co along with the substrate properties .and a less extent of plasticity index is obtained.
WC-CO-5mN
300secs
Fig4.26:Sectional View of the impacted sample WC-CO with a load of 5mN using FIB for 300sec.
When 5mN load for 300sec is applied onto the WC-Co having the coating thickness upto 750nm it will resist upto certain extent but due to the difference in the modulus of Film and substrate. Tensile stresses aroused at the interface of the coating and the substrate and initially interfacial crack can be seen later brittle fracture of the surface can be seen and as we see in the above picture crack propagating along the thickness can be seen and impact debris is formed here both adhesive and cohesive cracking along with the delamination of the coating were observed . When we apply load whole of it is taken by the coating itself and no or less amount of plastic deformation of the substrate can be seen.and also as we see the resistance to crack propogation is seen in WC-Co under the application of low load and even high load upto certain extent and a less quantity of plasticity index is obtained in WC-CO. when high loads are applied median cracks start generating and due to generation of residual stress by plastic deformation lateral cracks are been formed when the load is applied median cracks are formed and lateral cracks are closed.When the load is unloaded the vise-verse will happen.
HSS-5mN
15secs
Fig4.25:Sectional View of the impacted sample HSS with a load of 5mN using FIB for 15secs.
In the above figure HSS having a film thickness of about 650 nm .When compared to WC-Co HSS is a soft material .In the cross-sectional view of FIB we can observe the plastic deformation underneath the indenter as the thickness of the film is less when compared with film on WC-Co .thinning of the coating along with the plastic deformation can be seen for 15sec duration and even circumferential cracks can be seen This is due to the sliding along the intercolumnar grain boundaries. Here the failure is adhesive failure and fracture has occurred for a short period of time.
HSS-5mN
300secs
Fig4.25:Sectional View of the impacted sample HSS with a load of 5mN using FIB for 300secs.
In the above figure represents the cross-sectional view by FIB on HSS for 300sec impact duration.circumferential cracks can be seen in the picture these are due to sliding along the grain boundaries.As when compared with 15sec duration more amount of thinning and fracture has been seen in the 300sec duration.This HSS when compared WC-CO we haven’t seen any delamination or coating removal from the surface .so we can conclude that when compared to TiN on WC-CO TiN on HSS bears the load by substrate taking the load and some amount of plastic deformation can be visible. we see the H3/Er2 ratio the ratio will be higher for the WC-Co along with the substrate properties .and a less extent of plasticity index is obtained when compared with rest of them.
Inconel718-5mN
15secs
Fig4.25:Sectional View of the impacted sample Inconel718 with a load of 5mN using FIB for 15secs.
In the above figure Inconel718 having a film thickness of about 750 nm .Inconel is a soft material TiN is coated upon it .In the cross-sectional view of FIB we can observe the plastic deformation underneath the indenter .Thinning of the coating along with the plastic deformation can be seen for 15sec duration and even circumferential cracks can be seen.This is due to the sliding along the inter-columnar grain boundaries. Here the failure is adhesive failure and fracture has not occurred. Because due to the presence of modulus diference between the coating and the substrate ,When the load is applied the stiffer material i.e coatings tries to recover faster than the substrate and the substrate being softer recover slowly but the adhesion between them try to provoke the combined arrival because of the repeated impacts the bond will be weaken and the sliding or shearing along the grain boundaries takes place as the load goes on increasing delamination can be occurred. The through thickness cracks can be observed in sample.
Inconel718-5mN
300secs
Fig4.25:Sectional View of the impacted sample Inconel718 with a load of 5mN using FIB for 300secs.
In the above figure Inconel718 having a film thickness of about 750 nm .Inconel is a soft material TiN is coated upon it .In the cross-sectional view of FIB we can observe the plastic deformation underneath the indenter .more amount of Thinning of the coating along with the plastic deformation can be seen for 300sec duration when compared with 15sec duration of impact and even circumferential cracks can be seen.This is due to the sliding along the inter-columnar grain boundaries. Here the failure is adhesive failure and fracture has not occurred. Because due to the presence of modulus diference between the coating and the substrate ,When the load is applied the stiffer material i.e coatings tries to recover faster than the substrate and the substrate being softer recover slowly but the adhesion between them try to provoke the combined arrival because of the repeated impacts the bond will be weaken and the sliding or shearing along the grain boundaries takes place as the load goes on increasing delamination can be occurred. The through thickness cracks can be observed in sample due to the tensile stresses and bending stresses in the coating where the ductile substrate pulls the brittle coating downward[12].
SS Plate 304
15sec:
Fig4.25:Sectional View of the impacted sample SSPlate304 with a load of 5mN using FIB for 15secs.
In the above figure SS Plate304 having a film thickness of about 750 nm .SS plate304 is a soft material TiN is coated upon it .In the cross-sectional view of FIB we can observe the plastic deformation underneath the indenter . Thinning of the coating along with the plastic deformation can be seen for 15sec impact and even circumferential cracks can be seen.This is due to the sliding along the inter-columnar grain boundaries. Here the failure is adhesive failure and fracture has not occurred. Because due to the presence of modulus diference between the coating and the substrate ,When the load is applied the stiffer material i.e coatings tries to recover faster than the substrate and the substrate being softer recover slowly but the adhesion between them try to provoke the combined arrival because of the repeated impacts the bond will be weaken and the sliding or shearing along the grain boundaries takes place as the load goes on increasing delamination can be occurred. Columnar cracks are been seen in the picture.
SS Plate304
300secs
Fig4.25:Sectional View of the impacted sample SSPlate304 with a load of 5mN using FIB for 300secs.
In the above figure SS Plate304 having a film thickness of about 750 nm .SS plate304 is a soft material TiN is coated upon it .In the cross-sectional view of FIB we can observe the plastic deformation underneath the indenter .more amount of Thinning of the coating along with the plastic deformation can be seen for 300sec impact and even circumferential cracks can be seen.This is due to the sliding along the inter-columnar grain boundaries. Here the failure is adhesive failure and fracture has not occurred. Because due to the presence of modulus diference between the coating and the substrate ,When the load is applied the stiffer material i.e coatings tries to recover faster than the substrate and the substrate being softer recover slowly but the adhesion between them try to provoke the combined arrival because of the repeated impacts the bond will be weaken and the sliding or shearing along the grain boundaries takes place as the load goes on increasing delamination can be occurred. Columnar cracks are been seen in the picture.shear steps are formed where sliding along the inter-granular boundaries can be observed.Transgranular cracks are also seen due to the observed in sample due to the tensile stresses and bending stresses in the coating where the ductile substrate pulls the brittle coating downward[12]
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