Microstructure and Material Properties of Ti-15mass%Nb Alloy after Gas Nitriding and Quenching Process

Yoshikazu Mantani,Naoki Eguchi,Kentaro Shimada

doi:10.3390/cryst10121156

Abstract

The α′ martensite of Ti-15mass%Nb alloy exhibits high internal friction with high damping properties. However, its structure is smoother than the α + β structure. Therefore, a hardened surface layer is required for abrasion resistance. This study fabricated a martensite structure inside the nitriding layer by quenching, after gas nitriding at 1023 and 1223 K. Vickers hardness test, X-ray diffraction, scanning electron microscopy (SEM), and SEM-energy dispersive X-ray (SEM-EDX) measurements from the surface to the inside were made after the heat treatment process. In addition, the Young’s modulus and internal friction were calculated from the damping analysis. The α-TiN0.3 and β phase region was formed at approximately 80 µm from the surface at 1023 and 1223 K, and it was hardened. The internal friction of the gas nitriding and quenching specimens at 1023 and 1223 K was relatively high, though it did not reach that of the as-quenched specimen owing to the influence of the surface structure. From these results, it is considered that these material property values of the alloy can be controlled using the nitriding and quenching processes.

Highlights

Titanium and its alloys have been used as structural materials, various studies have employed its functional properties, such as low Young’s modulus E [1,2,3], shape memory effect [4,5,6], and super elasticity [6,7,8,9]
It is considered that the material property values of the alloy can be controlled by the gas nitriding and quenching process (GNQP) heat treatment
As a result of changing the hardness in the depth direction after GNQP, the region of α-TiN0.3 and β phase was formed at approximately 80 μm at 1023 and 1223 K, and this region was hardened

Summary

Introduction

Titanium and its alloys have been used as structural materials, various studies have employed its functional properties, such as low Young’s modulus E [1,2,3], shape memory effect [4,5,6], and super elasticity [6,7,8,9]. Martensite structure of the Ti-15mass%Nb alloy exhibits high internal friction Q−1 with high damping properties [10,11,12]. A hardened surface layer is required for abrasion resistance. The nitriding is often performed as a typical surface treatment method for hardening a titanium alloy. There are few reports on the nitriding of Ti-Nb alloy systems or the martensite structure of titanium alloys

Methods

Results

Conclusion