Investigation of shot blasting and thermal stress relieving processes on residual stresses and corrosion behavior of X60 steel gas pipelines

Abstract

Corrosion is one of the most common complications in some industries. Two main factors causing corrosion are tensile stress and a corrosive environment, both of which require careful control. The purpose of this research is to achieve an optimal method of increasing corrosion resistance and also reducing tensile residual stress in API X60 gas pipelines. In the present study, residual stress has been examined in samples which have undergone either shot blast or heat treatment operations or both of them. In this research, 4 samples have been studied including: shot blasted, firstly heat treated then shot blasted, firstly shot blasted then heat treated and heat-treated using API-X60 steel pipe to indicate the best method of resistance to corrosion and stress. To investigate these properties, residual stress of these components has been examined by using the Contour Method and corrosion resistance has been studied through the Cyclic Polarization Resistance method. The results showed that the best corrosion resistance happen by the heat-treated sample (almost twice as much as the other methods) and also the most compressive residual stress observe in the firstly shot blasted and then heat-treated sample.

A novel approach for nondestructive depth-resolved analysis of residual stress and grain interaction in the near-surface zone applied to an austenitic stainless steel sample subjected to mechanical polishing

“…Control of RS is particularly important in surface layer and coating deposition. The advantages of a subsurface stress state, usually of the compressive type, can be achieved by different treatments such as mechanical shot peening [1,8], laser shock peening/ hardening [1,3,9], surface mechanical attrition treatment [2], and shot blasting [10].…”

“…This means that the application of direct stress scanning with a predefined gauge volume is not suitable for measuring stress gradient in the subsurface region up to a few µm [9]. This is a major disadvantage because important stress gradients are often present close to the surface, especially in the case of mechanically treated materials or deposited coatings [1][2][3][8][9][10].…”