Hardfacing Alloy Classification
The TIG welders, MIG welders, Arc welders and Stick welders are pleased that the American Society for Metals Committee on Hardfacing has organized a hardfacing alloys classification. Thanks to that, the multiprocess welders can recognize five main groups of these alloys, where the division is based on their alloy content. We already presented group 1 – the low-alloy steels with the main alloying element in being chromium and their two subgroups. The multiprocess welders should also recognize the other four groups, namely:
Group 2 – these are the alloyed steels with higher content. The group also has two subgroups. The first one has chromium being the chief alloying element that has total alloy content of 12-25 %. Some of these alloys also contain molybdenum. The second subgroup has molybdenum as the principal alloying element, yet some of them also contain chromium. MIG welders, TIG welders, Stick welders and Arc welders know that the alloyed steels from this second group are more wear resistant, though less shock resistant and are also more expensive that the alloyed steels in Group 1. Since they have high compressive strengths they are also suitable for rebuilding of worn parts. At normal temperatures these alloys have high impact resistance and good abrasion resistance.
There are to other subgroups here as well. The third subgroup includes tungsten and modified high-speed tool steels. These steels are suitable for temperatures up to 590°C. These alloys are used when the multiprocess welders need toughness and good resistance. The fourth subgroup features austenitic manganese steels that contain or molybdenum and nickel. These alloys have high shock resistance, yet limited wear resistance. The alloy content in them is between 12 and 25 %.
Group 3 are the alloys with 25 – 50 % alloy compositions. These are high-chromium alloys, where some of them contain molybdenum, nickel, or both. The multiprocess welders use the alloys in this group when they are searching for good impact and good erosion resistance. These alloys are more expensive than the alloys in groups 1 and 2.
Group 4 are the nonferrous alloys that the MIG welders, TIG welders, Stick welders and Arc welders. They are on a nickel or on a cobalt base and the nonferrous metals content in them varies from 50 to 99%.
Group 5 that the multiprocess welders know about are based on tungsten carbide particles distributed in a metal matrix. The matrix metals have carbon steel, iron, as well as alloys based on copper, cobalt and nickel. They have excellent corrosion and abrasion resistance.