© 2012 Su-Jin Kim GNU Surface & Metrology Manufacturing Processes 4. Surface & Metrology

© 2012 Su-Jin Kim GNU Surface & Metrology Manufacturing Processes Index Surface roughness Friction, wear Surface treatment & Coating Metrology

© 2012 Su-Jin Kim GNU Surface & Metrology Manufacturing Processes Surface Structure ( 표면 구조 ) Contaminant ( 불순물 ) Oxide ( 산화물 ) Fe 2 O 3, Al 2 O 3, Cu 2 O, CrO Surface structure( 표면구조 ): work-hardened layer( 가공경화층 ), residual stress( 잔류응력 ) Metal substrate( 모재 ) nm Contaminant nm Oxide μm Surface structure Metal substrate stress

© 2012 Su-Jin Kim GNU Surface & Metrology Manufacturing Processes Stylus Surface Roughness ( 표면 거칠기 ) Arithmetic average ( 산술평균 ) Center line average ( 중심선평균 ) Root-mean-square average ( 제곱평균 ) Maximum roughness height ( 최대높이 ) R t y y 1 y 2 … …y n Surface profile data Center line

© 2012 Su-Jin Kim GNU Surface & Metrology Manufacturing Processes Friction ( 마찰 ) Friction is defined as the resistance to relative sliding between two contact bodies under load. Adhesion( 융착 ) theory of friction: Two clean surfaces contact at only small area. Real area of contact, A r N F Normal force, N Friction force, F A r <<A A r <AA r ~A Sliding Bending Sheet forming Forging Drawing Metal cutting

© 2012 Su-Jin Kim GNU Surface & Metrology Manufacturing Processes Wear( 마멸 ) Adhesive ( 융착 ) Abrasive ( 연삭 ) Corrosive ( 부식 ) Fatigue ( 피로 )

© 2012 Su-Jin Kim GNU Surface & Metrology Manufacturing Processes Lubricant ( 윤활 ) Oil Zinc phosphate( 인산아연 ) conversion coating( 전환피복 ) for carbon steel: Chemical reaction with acid generates rough surface that contains lubricant reducing friction at forging and drawing. Oxalate( 수산염 ) conversion coating for stainless steel. How lubricant

© 2012 Su-Jin Kim GNU Surface & Metrology Manufacturing Processes Surface treatment ( 표면처리 ) Shot peening Roller burnishing Impact with high speed metal ball Compressive residual stress Roller Compressive residual stress Burnishing

© 2012 Su-Jin Kim GNU Surface & Metrology Manufacturing Processes Surface Coating ( 표면코팅 ) Physical vapor deposition(PVD, 물리증착 ): deposit vaporized material onto workpiece surface in vacuum and at high temperature. PVD Lab. PVD Tools

© 2012 Su-Jin Kim GNU Surface & Metrology Manufacturing Processes Surface Coating Electroplating( 전기도금 ): Metal ions(+) in a solution are moved by an electric field to coat an cathode(-) electrode. Zn ++ SiO 4 -- Zn ++ SiO 4 -- H+H+ (-) (+) Zn Electroplating

© 2012 Su-Jin Kim GNU Surface & Metrology Manufacturing Processes Surface Coating Anodizing( 양극처리 ): an electrolytic oxidation process used to increase the thickness of the natural oxide layer on the surface of metal parts connected to anode(+). Aluminum alloy are anodized to increase corrosion resistance, surface hardness, and to allow coloring. O2-O2- (-) (+) O2-O2- Al Air bubble Anodizing

© 2012 Su-Jin Kim GNU Surface & Metrology Manufacturing Processes Surface Coating Phosphate conversion coating ( 인산염 피막 ) are used on steel parts for corrosion resistance, lubricity, painting foundation. Phosphoric acid( 인산 ) chemically react with the surface of the part being coated to form a layer of insoluble, crystalline phosphates. Manganese phosphates( 인산망간 ) are used both for corrosion resistance and lubricity. Iron phosphates( 인산철 ) are typically used as a base for further coatings or painting. Zinc phosphates( 인산아연 ) are used for rust proofing (P&O), a lubricant base layer, and as a paint/coating base.