Arc Thermal Spray NiCr20 Alloy Coating: Fabrication, Sealant, Heat Treatment, Wear, and Corrosion Resistances

Van Tuan Nguyen,Quy Le Thu,Quoc Cuong Ly,Ha Pham Thi,Ly Pham Thi,Thanh Dinh Thi Mai,Tuan Anh Nguyen

doi:10.1155/2019/8796958

Abstract

This study presents the effect of heat treatment on porosity, phase composition, microhardness, and wear and corrosion resistances of the thermal sprayed NiCr20 coating after sealing with aluminum phosphate. The annealing temperatures were varied in a range of 400 to 1000°C. The obtained results indicated the porosity of coating decreased with increasing the annealing temperature. After treatment at temperatures in range of 800-1000°C, more than 90% of initial pores in the coating were successfully filled with the sealants. The XRD data revealed not only the formation of new phases of other compounds, but also the interaction between coating and sealant. After heat treatment, wear resistance of coating was 12 times higher than that without heat treatment. The corrosion test in H2SO4 solution indicated that the presence of sealant in coatings increased their corrosion resistance. From these findings, application of these NiCr20 coatings to protect steel against wear and corrosion appears very promising.

Highlights

For the thermal spray coatings in corrosive environments, their intrinsic porosity could facilitate the ingress of corrosive agents, resulting in the initiation of corrosion leading to the coating delamination
There was a lack of information about the effect of heat treatment on property and structure of the aluminum phosphate sealed NiCr20 coatings
We present our research on the effect of heat treatment on porosity, phase composition, microhardness, and wear and corrosion resistances of the thermal sprayed

Summary

Introduction

For the thermal spray coatings in corrosive environments, their intrinsic porosity could facilitate the ingress of corrosive agents, resulting in the initiation of corrosion leading to the coating delamination. The post-heat treatment after spraying process is necessary This posttreatment process could be carried out by using various techniques, such as the laser or electron-beam surface melting, alloying method, hot isostatic pressing (HIP), chemical vapor deposition (CVD), and chemical vapor infiltration (CVI). The influence of temperature on porosity and wear resistance of thermal coating after sealing with aluminum phosphate has been reported [8,9,10]. There was a lack of information about the effect of heat treatment on property and structure of the aluminum phosphate sealed NiCr20 coatings. We present our research on the effect of heat treatment on porosity, phase composition, microhardness, and wear and corrosion resistances of the thermal sprayed.

Experimental

Results and Discussion

Conclusions