Abstract
This study aimed to improve the bending strength and reliability of ceramics using laser peening (LP). In the experiment, LP without coating (LPwC) and with coating (LPC) were applied to silicon nitride (Si3N4) under various conditions. The surface roughness, residual stress, and bending strength were then measured for the non-LP, LPwC, and LPC specimens. The results show that the LPwC specimen had a greater surface roughness but introduced larger and deeper compressive residual stress when compared with the non-LP and LPC specimens. In addition, the bending strength of the LPwC specimen was higher and scatter in bending strength was less compared with the non-LP and LPC specimens. This may be attributed to the transition of the fracture initiation point from the surface to the interior of the LPwC specimen because of the compressive residual stress introduced near the surface. Thus, it was demonstrated that the application of LP is effective in improving the strength and reliability of ceramics.
Highlights
Ceramics are used in the manufacturing of sliding parts and high-temperature structural parts owing to their excellent heat, wear, and corrosion resistance when compared with metals
Koike et al clarified that the abrasion resistance can be improved by introducing compressive residual stress through shot peening (SP) [7], while Shukla et al reported an improvement in the fracture toughness value of zirconia through fine particle peening [8]
The maximum depth of the fracture origin of the nonLP specimen was approximately 25 μm, whereas the fracture origin of LP without coating (LPwC)-1 was deeper than 60 μm. These results indicate that the compressive residual stress introduced by laser peening (LP) suppressed the crack initiation from the surface and, as a result, the fracture origin shifted to inside of the material in LPwC-1
Summary
Ceramics are used in the manufacturing of sliding parts and high-temperature structural parts owing to their excellent heat, wear, and corrosion resistance when compared with metals. It has previously been reported that shot peening (SP) introduces compressive residual stress and improves apparent fracture toughness [1,2,3]. Moon et al showed that SP can be applied to silicon nitride (Si3N4) to introduce compressive residual stress and improve the apparent fracture toughness [2]. Tanaka et al reported that fine particle peening and ultrasonic peening can be applied to Si3N4 to improve the apparent fracture toughness [3]. Koike et al clarified that the abrasion resistance can be improved by introducing compressive residual stress through SP [7], while Shukla et al reported an improvement in the fracture toughness value of zirconia through fine particle peening [8]
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