Microstructural evolution of laser clad Stellite 31 powder on Inconel 713 LC superalloy

Abstract

Nickel-based alloys are one of the major material groups broadly utilized in the aerospace industry. Inconel 713 LC is a nickel-based superalloy designed for structures requiring high strength at high temperatures. The surface characteristics of Inconel 713 LC can be ameliorated by cladding with Stellite 31 powder. In the present study, Inconel 713 LC was clad with Stellite 31 powder by pulsed Nd:YAG laser. The influence of laser parameters ranging from frequency, pulse width, and speed was discussed on the hardness and microstructural features of the clad zones. The results illustrated that the upper zone of the clad consisted of very fine coaxial grains and dendrites grown in different directions. The middle part consisted of a uniform distribution of homogeneous coaxial grains. Columnar and coaxial grains were observed at the interface of coating-substrate. An increase in the heat input induced by raising the pulse width and frequency or reducing laser speed caused the coaxial grains to turn into columnar ones. The cobalt solid solution phase and Cr 7 C 3 , Cr 3 C 2 , W 2 C, and WC x carbides were formed in the cladding zone. An increase in the laser frequency and pulse width and decrease in the laser speed led to an enhancement in the dissolution of the substrate in the cladding zone. As the dilution ratio increases, the hardness decreases approximately linearly. The maximum hardness in the cladding zone was about 482 ± 10 Hv. It was substantially higher than that of the substrate as 355 ± 3 Hv that can be ascribed to the presence of Cr 7 C 3 , Cr 3 C 2 , W 2 C, and WC x carbides in the cladding zone. Besides the cladding zone, intermixing and heat-affected zones were formed at the interface of coating-substrate. The thickness of the intermixing zone depending upon the laser conditions varied between 8 and 20 μm. The hardness of intermixing and heat-affected zones was less than the cladding zone. • The cladding zone consists of γ-Co and Cr 7 C 3 , Cr 3 C 2 , W 2 C, and WC x carbides • The upper zone includes fine coaxial grains and dendrites grown in different directions. • The middle zone consists of a uniform distribution of homogeneous equiaxed grains. • Columnar and coaxial grains are observed at the interface of coating-substrate. • The maximum hardness value of clad zone is approximately 482 ± 10 Hv.