Load dependence of microhardness of hard coatings

• Published in: Surface & coatings technology Vol. 36; no. 3-4; pp. 683 - 694
• Main Authors: Jindal, Prem C., Quinto, Dennis T.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 15.12.1988; Elsevier
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Metals, semimetals and alloys; Metals. Metallurgy; Nonmetallic coatings; Physics; Production techniques; Specific materials; Surface treatment; Hardness test; Hafnium nitride; Zirconium nitride; Vickers test; Titanium nitride; Cutting tool; Measurement method; Non metal coatings; Non metal coating; Microhardness; Knoop hardness
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/0257-8972(88)90009-6

Vickers and Knoop microhardness measurements on hard coatings on WC-Co substrates were studied as a function of indentation load. It is shown that the increase in conventional Vickers hardness with decreasing load, i.e. the indentation size effect, can be derived by considering the elastic recovery in indent length on unloading. It further follows that the large increase in microhardness at light loads (up to 100 gf) depends inversely on the elastic modulus of the hard coating. Microhardness numbers based on Vickers or Knoop diagonal measurements are shown to have varying sensitivity to the elastic recovery effect. Depending on coating thickness, the microhardness- load profiles can indicate the existence of gradient residual stresses in the coatings as well as effects due to the coating-substrate interface and the substrate hardness.