Alloy 35Mo is a new versatile Ni-alloy which has corrosion and mechanical properties comparable to advanced Ni-base alloys, with the benefit that it can be processed like a stainless steel. The alloy was recently designated UNS N08935 with the composition 35Ni-30Fe-27Cr-6.5Mo-0.28N and has a PREN of 52. This paper presents the mechanical and physical properties of the material and results from corrosion testing. Corrosion results from general corrosion testing in acid environments, together with results from stress corrosion cracking testing in chloride environments and pitting corrosion testing show that UNS N08935 can be used in harsh environments in many applications, e.g. heat exchangers in refinery industry and equipment with seawater cooling. UNS N08935 also has high mechanical strength, and good weldability has been shown using Alloy 59 as filler metal.

INTRODUCTION

Material selection in refinery and chemical industry is often challenging and several aspects needs to be taken into consideration, such as mechanical properties, maximum application temperature, pitting corrosion resistance, acid corrosion resistance, and weldability. Commonly used stainless steels often have limitations in one or more of these areas, and it might be necessary to select advanced and costly Ni-based alloys. Alloy 35Mo, recently designated UNS N08935, is a new versatile Ni-alloy which has corrosion and mechanical properties comparable to advanced Ni-base alloys, with the benefit that it can be processed like a stainless steel. The composition is 35Ni-30Fe-27Cr-6.5Mo-0.28N and the alloy has a PREN of 52, calculated with the formula; PREN = %Cr + 3.3 × (%Mo + 0.5%W) + 16%N. The nickel content is high enough to ensure good structure stability; however, considerably lower than in many advanced Ni-base alloys. UNS N08935 will be sold under the trade name Sanicro® 35†.

Some data has been presented for UNS N08935 (Alloy 35Mo) seamless tubing including excellent pitting resistance with a critical pitting temperature (CPT) above 100°C in 3 M MgCl2, tested in delivery condition. High mechanical strength has been demonstrated as examples from heat exchanger tubes with yield strengths above 470 MPa. Good weldability has also been demonstrated with Alloy 59 as filler material; however, to be able to consider a new material additional information is required.1,2

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