ABSTRACT

The issue of hardness testing and nickel base alloys has been a contentious topic in the oil and gas community. In this paper we present the uses of hardness testing with respect to nickel base alloys with examples of limitations and applications. As hardness has historically been seen as a factor for predicting environmental cracking resistance of nickel base alloys, a literature assessment of slow strain rate data is presented examining the potential for a relationship between the hardness and the alloy's resistance to environmental cracking. More recent studies tried to access the mechanisms behind the environmental cracking issue and their results are reviewed.

The paper concludes that there is no reliable relationship between hardness and environmental cracking resistance on nickel base alloys and proposes some actions as a result.

INTRODUCTION

This paper addresses the relationship between hardness and environmental cracking resistance in nickel base alloys. The work here builds on the presentation made to AMPP's SC08 Fall 2021 meeting on October 19th.1

We use hardness as a measure of acceptance for a number of material property attributes. Some examples include using hardness values to indicate strength level, stiffness, resistance to scratching or abrasion, wear resistance, weldability, heat treat condition and resistance to environmental cracking. The accuracy or value of hardness to predict or estimate these characteristics lies in the relationship between hardness and the characteristic of interest. Hardness is the resistance to indentation. For some of these predictive characteristics, the relationship is pretty straightforward, for others, much more tenuous.

Hardness testing is universally used as a basic quality assessment tool for materials because of its simplicity of use, speed at which results are obtained and relatively low cost to apply. In addition to the relevance of the test method to assess the attribute of interest, we need to also be cognizant of the test details and the potential sources of variability and error. This is briefly discussed below.

Keywords:
upstream oil & gas, production chemistry, h2s management, hardness, riser corrosion, oilfield chemistry, corrosion management, united states government, pipeline corrosion, metals & mining
Subjects:
Production Chemistry, Metallurgy and Biology, Pipelines, Flowlines and Risers, Materials and corrosion, Corrosion inhibition and management (including H2S and CO2)
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