دانلود رایگان ترجمه مقاله آنالیز روش اندازه گیری میکرو سختی برای توصیف پوشش های سخت (نشریه الزویر 2003)

تحلیل رویکرد اندازه گیری میکروسختی برای مشخصات روکش های سخت

The analysis of microhardness measurement approach for characterization of hard coatings

Abstract

The analysis of problems concerning thin film (1–5 μ) microhardness measurement by means of different techniques is conducted in case of diamond-like carbon coatings. It is shown experimentally that the extrapolation of the lg(Hm−Hs) vs. d dependence to zero d values, where Hs is microhardness of the film substrate, Hm is formal microhardness of the substrate with coating and d is Berkovich pyramid depth, leads to reliable coating microhardness values Hf independent on substrate properties and characterizing the properties of the coating itself. This approach is used to obtain the average Hf values of multilayer coatings. It is found that the surface roughness of the coatings impedes the correct determination of the coating microhardness by means of nano-indentor techniques. The coating surface smoothening (mechanical or by ion etching) provides the conditions for correct microhardness measurement. It is concluded that the real Hf values of diamond-like carbon coatings obtained by pulse arc graphite sputtering exceeds 100 GPa.

1 Introduction

Microhardness is often used to characterize the strength of solid materials and strengthening coatings, since it is the property which is easy to measure. However, a common way of microhardness (H) measurement (by measuring the imprint size of diamond pyramid at loads commonly exceeding 200 mN) in the case of thin (approx.1–5 mm) hard coatings usually gives only an effective value Hm w1x, which differs from the microhardness of coating (Hf) itself, because at such loads the coating during measurement is deformed together with the underlying substrate material.This leads to the dependence of the effective value Hm on the load (Fig.1) w2x.In this case, the dependence of the indentor depth (d) upon load (P) can be used for determining the actual value of Hf.The recent progress in nano-techniques w3x, allows significantly reducing the load values (F20 mN) and thus the ability of direct microhardness measurement for hard coatings.In the present paper, a comparison of both approaches (common and nano-) for the determination of Hf values in case of diamond-like carbon coatings (DLC) and multilayer Ti–C films has been performed in three runs and discussed.