Ultrasonic Nanocrystal Surface Modification Technology

Abstract

Ultrasonic nanocrystal surface modification (UNSM) technology is a novel surface modification technology that can improve the mechanical and tribological properties of interacting surfaces in relative motion. UNSM treatment was utilized to improve the wear resistance fatigue strength of slim bearing rings made of SAE52100 bearing steel without damaging the raceway surfaces. In this study, wear and fatigue results that were subjected to different impact loads of the UNSM treatment were investigated and compared with those of the untreated specimen. The microhardness of the UNSM-treated specimens increased by about 20%, higher than that of the untreated specimens. The X-ray diffraction analysis showed that a compressive residual stress of more than 1,000 MPa was induced after the UNSM treatment. Also, electron backscatter diffraction analysis was used to study the surface structure and nanograin refinement. The results showed that the rolling contact fatigue life and the rotary bending fatigue strength of the UNSM-treated specimens increased by about 80% and 31%, respectively, compared to those of the untreated specimen. These results might be attributed to the increased microhardness, the induced compressive residual stress, and the nanocrystal structure modification after the UNSM treatment. In addition, the fracture surface analysis showed that the fish eye crack initiation phenomenon was observed after the UNSM treatment.

Intergranular Corrosion of 316L Stainless Steel by Aging and UNSM (Ultrasonic Nano-crystal Surface Modification) treatment

“…잔류응력을 개선하는 방법 중에서 UNSM 처리는 초음파 진동에너지를 이용한 큰 하중이 부가된 볼로 1 초에 20,000 번 이상 금속 표면을 타격하는 방법인데, 탄성 및 소성을 발생시켜 표면 층의 조직을 나노결정 조직으로 개질시키면 서 아주 크고 깊은 압축잔류응력을 형성시킨다 16) . 지금까 지의 표면처리 기술들은 정적인 하중만 부가하거나 동적인 하중만을 부가하였지만, UNSM 처리는 정적 하중에 동적 19) .…”

Variations in Tribology Factors of SM45C by UNSM Modification

“…(Pyun et al, 2012;Suh et al, 2007). (Pyun et al, 2012;Suh et al, 2007) 3.2 트라이볼러지 시험후의 SEM관찰 결과 3.2.1 SM45C재의 미처리재의 SEM관찰 결과 Fig. 16은 큰 시편의 중앙부를 SEM 관찰 한 것으로, 트라이볼 로지 시험 약 20초 후의 미처리 소재의 표면을 예시한 것이다.…”

Variations in Tribological Characteristics of SM45C by PVD Coating and Thin Films

“…2.1 초음파 나노표면 처리법에 따른 시험편의 분류 (Amanov et al, 2012;Amanov et al, 2014;Lee et al, 2015;Suh et al, 2007).…”

“…소재는 현재 STS 304L(오스테나이트계 스테인레스강) 등이 널리 사용되고 있다 (Chun et al, 2009;Kim et al, 2010;Kim et al, 2011Yu et al, 2013;Suh et al, 2016 (Amanov et al, 2012;Amanov et al, 2014;Gim and Jeong, 2007;Jeon et al, 2014;Lee et al, 2015;Pyun et al, 2012;Suh et al, 2016).…”