Mechanical strength of ground WC-Co cemented carbides after coating deposition

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:689

Article

Yang, J.^1,2,6  Oden, M.²  Johansson-Joesaar, M. P.^2,3  Esteve, J.⁴  Llanes, L.^1,5 

[1] Univ Politecn Cataluna, CIEFMA, Dept Ciencia Mat & Engn Metaburgica, Campus Diagonal Besos EEBE, Barcelona 08019, Spain

[2] Linkoping Univ, Dept Phys Chem & Biol IFM, Nanostruct Mat, S-58183 Linkoping, Sweden

[3] SECO Tools AB, S-73782 Fagersta, Sweden

[4] Univ Barcelona, Dept Fis Aplicada & Opt, Barcelona 08028, Spain

[5] Univ Politecn Cataluna, CRnE Ctr Res Nanoengn, Campus Diagonal Besos EEBE, Barcelona 08019, Spain

[6] Pol Ind Les Fallulles, AMES Sintered Met Components, Cami Can Ubach,8 Sant Vicenc Horts, Barcelona 08620, Spain

关键词: Cemented carbides;    Grinding;    Coating;    Ion etching;    Surface integrity;    Transverse rupture strength;   

DOI  :  10.1016/j.msea.2017.02.034

来源: Elsevier

【 摘 要 】

Manufacturing of hardmetal tools often involves surface grinding, ion etching and final coating. Each stage throughout the manufacturing chain introduces surface integrity changes which may be critical for defining the final mechanical behavior of the coated tools. Within this context, an experimental test program has been developed to assess the influence of a coating (TiN) deposition on surface integrity and transverse rupture strength of a previously ground fine-grained WC-Co grade substrate. Four different substrate surface finish conditions (prior to ion etching and coating) were evaluated: as sintered (AS), ground (G), polished (P), and ground plus high temperature annealing (GTO. Surface integrity and fracture resistance characterization, complemented with a detailed fractographic analysis, were performed on both uncoated and coated samples. Results show that the surface integrity after grinding has been partly modified during the ion etching and film deposition processes, particularly in terms of a reduced compressive residual stress state at the substrate surface level. Consequently, the grinding induced strength enhancement in hardmetals is reduced for coated specimens. Main reason behind it is the change of nature, location and stress state acting on critical flaw: from processing defects existing at the subsurface (uncoated G specimens) to grinding-induced microcracks located close to the interface between coating and substrate, but within the subsurface of the latter (coated G specimens). This is not the case for AS and P conditions, where flexural strength does not change a result of ion etching and coating. Finally, fracture resistance increases slightly for GTT specimens after coating process, possibly caused by a beneficial effect of the deposited film on the residual stress state at the surface.

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