Mechanical strength of ground WC-Co cemented carbides after coating depositionShow others and affiliations
2017 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 689, p. 72-77Article in journal (Refereed) Published
Abstract [en]
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.
Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA , 2017. Vol. 689, p. 72-77
Keywords [en]
Cemented carbides; Grinding; Coating; Ion etching; Surface integrity; Transverse rupture strength
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:liu:diva-136581DOI: 10.1016/j.msea.2017.02.034ISI: 000397698600010OAI: oai:DiVA.org:liu-136581DiVA, id: diva2:1090001
Note
Funding Agencies|MINECO/FEDER [MAT 2015-70780-C4-3-P]; Erasmus Mundus joint European Doctoral Programme DocMASE
2017-04-212017-04-212018-03-19