A certified reference material for the scratch test

Abstract

Adhesion and other mechanical behaviour of coatings is at present routinely tested in industry and research organisations using the scratch test. The test has been the subject of a European Standard prEN 1071-3:2000 established by the European Standards Committee CEN TC184 WG5. A previous European project on the development and validation of test methods for thin hard coatings-FASTE-revealed that uncertainties in the Rockwell C stylus tip shape represent a major source of error for the scratchtest method. Therefore a follow-up project-REMAST-was started to develop and certify a reference material as a quality control tool for the testing and qualification of scratch-test instruments. In addition, a considerable effort was devoted to improve the scratch stylus manufacturing process. This paper presents the results of the REMAST project. During a feasibility study, two candidate materials-titanium nitride (TiN) and diamond-like carbon (DLC) coatings both on high speed steel substrates-were evaluated. Because of the lower sensitivity to styli tip shape variations and higher data scatter observed for the TiN coating, DLC was chosen as the reference material to be certified. One thousand samples were produced, as well as qualified styli to carry out the certification campaign, including homogeneity and stability testing. Nine independent laboratories were involved in the certification exercise, and the data were statistically analysed to obtain the certified critical load values and their uncertainty ranges. A certified reference material BCR-692 is available for verification purposes. This presents three repeatable failure events at certified critical load intervals and can provide a good indication of overall scratch-test instrument performance, including stylus condition and calibration. It is also useful as a diagnostic tool, providing a means of sensitive monitoring of machine and stylus performance over extended periods. Considerable improvement of the quality of scratch styli was achieved by the strict control of all manufacturing steps.

Synthesis, structural and mechanical characterization of sputtered tungsten oxide coatings

“…The load was increased linearly from 0 up to 50 N using Rockwell C indenter tip with a radius of 200 Am, loading speed of 100 N/min and scratch speed of 10 mm/min. The critical loads (L c ) values corresponding to the different failure mechanisms (adhesive/cohesive) were measured by analyzing the failures events in the scratch track by optical microscopy, for more details see [8].…”

The investigation of adhesion and fatigue properties of TiN/TaN multilayer coatings

“…This method is easy and quick. [35][36][37] To determine fatigue behaviour of coatings, multi-pass scratch test is used. In this method, failure criterion is the number of cycles that causes damage.…”

Influence of Nitrogen Gas Flow Rate on The Microstructural and Mechanical Properties of Tin Deposited Carbon Steel Synthesized by Cae

“…Jacobs et al [25] has identified four main failure events for TiN coatings on HSS coupons: longitudinal cracks at the track edges (Lc1), semicircular coating cracks inside the scratch tracks (Lc2), cohesive chipping at the tracks edges (Lc3), and spallation at the track edges (Lc4). When the normal load applied on the indenter increases, plough-like channels appear in the scratch trace.…”