Influence of Xe Ion-Bombardment on the Substrate Microstructure and the Residual Stresses of Tin Coatings Deposited by Plasma Reactive Sputtering onto AISI 4140 Steel

Thaís Helena Carvalho Miranda,Pedro Brito,Fernando Alvarez,Jose Luis Garcia,Erika Ochoa Becerra,Sandra Vales,Haroldo Pinto,Roosevelt Droppa

doi:10.4028/www.scientific.net/amr.996.841

Abstract

The seek for sustainability in the global economic scenario has led to the need for developing materials that provide higher productivity, greater speed of operation, extended lifetimes and enhanced surface finishing of engineering parts. To achieve these goals it is essential to modify the metal surface with respect to its behavior in situations of friction, wear and oxidation at high temperatures. In this work, we studied the impact of different surface treatment strategies involving atomic peening with Xe ions and low temperature plasma nitriding on the surface microstructure of AISI 4140steel and the consequences of those surface treatments on the residual stresses of TiN coatings deposited onto the pre-treated substrates. The results show that ion bombardment at 1000 eV leads to mainly sputtering of surface material and no appreciable surface activation could be obtained for the subsequent plasma nitriding treatment. In the sample subjected to simple plasma nitriding, the highest nitride content was found and a Ti-enriched transition zone deposition appears to build up during the coating deposition. Accordingly the residual stresses of the TiN coatings deposited onto the nitrided steel surface were significantly lower in comparison to those encountered in the coatings grown on the non-treated, only bombarded and bombarded followed by nitriding substrates.

Highlights

Coatings of transition metal nitrides have been widely used in engineering tools and dies mainly due to their high hardness, high thermal and chemical stability and corrosion resistance [1]
Residual stresses are typically generated within coated metal-matrix composites owing to the thermal expansion mismatch between the hard coating and the metal substrate that arises during the cooling stage in the manufacturing of tools and dies
The TiN coating in all cases has an average thickness of 400 nm

Summary

Introduction

Coatings of transition metal nitrides have been widely used in engineering tools and dies mainly due to their high hardness, high thermal and chemical stability and corrosion resistance [1]. Residual Stresses IX shown to cause grain refinement within the near-surface region, enhancing the diffusion of nitrogen into the steel surfaces [2,3] This process can be applied to modify the substrate surface at the atomic level, making it harder and increasing the coating adhesion to the pre-treated substrate [4,5]. Residual stresses are typically generated within coated metal-matrix composites owing to the thermal expansion mismatch between the hard coating and the metal substrate that arises during the cooling stage in the manufacturing of tools and dies. The application of surface pre-treatments modifies the phase composition within the metal surfaces This may have a great impact on the thermal mismatch between coating and substrate, contributing to tailor the residual stresses in the final products. All three strategies were accompanied by a final TiN coating deposition according to the so-called duplex coating strategy

Experimental Details Substrate materials

Results and Discussion

Conclusions