Effects of TIG surface melting and chromium surface alloying on microstructure, hardness and wear resistance of ADI
Microhardness and wear resistance of different microstructures formed by TIG (tungsten inert gas) surface melting and chromium surface alloying (using ferrochromium) of ADI (austempered ductile iron) were studied. Surface melting resulted in the formation of a ledeburitic structure in the melted zone, and this structure has a hardness up to 896 HV as compared to 360 HV in that of ADI. Moreover, chromium surface alloying resulted in the formation of different structures including: (1) a hypereutectic structure consisting of primary (Fe,Cr)7C3 carbides and a eutectic matrix of transformed austenite (into martensite and retained austenite) , as also (Fe,Cr)7C3 carbides, with a hardness of 1078 HV; (2) a hypoeutectic structure consisting of the same eutectic along with transformed primary austenite, with a hardness of 755 HV; and (3) a ledeburitic structure with an acicular morphology and a hardness of 896 HV. The results also indicated that surface melting reduced the wear rate of the ADI by approximately 37%. Also, chromium surface alloying yielded a superior wear behavior and reduced the wear rate of the treated specimens by about 38% and 70%, depending on the structures formed.
Key wordsductile iron surface alloying surface melting chromium wear resistance
Unable to display preview. Download preview PDF.
- 1.Hayrynen K L, Brandenberg K R, Keough J R. Austempered Gears and Shafts: Tough Solutions [J]. Gear Technology, 2001, 18 (2): 42.Google Scholar
- 3.Nagai T, Fujioka J, Hattori H, et al. Iron Casting With Mo-Alloyed and W-Alloyed for Wear Resistance and Laser Surface Modification-Laser Surface Modification of Cast Iron Aimed at Refining the Wear Resistance [J]. Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society, 2004, 22 (1): 132 (in Japanese).Google Scholar
- 8.Hiraoka T, Nakamora Y, Tanaka Y. Mechanical Properties of Cast Iron Surface-Hardened by TIG Arc Remelting [J]. Transactions of the American Foundrymen’s Society, 1995, (102): 603.Google Scholar
- 9.Wladyslaw A, Orlowicz, Trytek A. Susceptibility of Iron Castings to Heat Absorption From an Electric Arc and to Hardened-Layer Shaping [J]. Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, 2003, 34A (12): 2973.Google Scholar
- 17.Hutchings I M. Tribology: Friction and Wear of Engineering Materials [J]. Cambridge: Edward Arnold, 1992.Google Scholar