©
COPYRIGHT 2000 THE ESAB GROUP, INC. LESSON
VIII
HARDSURFACING
ELECTRODES 8.1 INTRODUCTION
Hardfacing, or
hard surfacing*, has been used as a method of reclaiming
industrial parts and
equipment since the early 1920’s. At that time, it was found that a
hard alloy deposit, properly
applied to the surface of oil drilling bits, extended the life of those bits by
more than ten
times. Since then, hardfacing has become universally accepted as an economical
and practical means of restoring plant
and field equipment subjected to destructive wear. 8.1.1
Definition
and Purpose
- Hardfacing may be defined as the application of a
hard, wear resistant alloy to the surface
of a softer metal to restore it dimensionally and reduce
wear caused by abrasion, impact, erosion, corrosion and heat.
8.1.1.1 Lubrication
of machine parts is an effective method of preventing abrasive wear;
however, in applications such as the
external parts of farm and earth moving equipment, oil drilling
tools, engine valves, etc., lubrication is not possible. In these applications,
hardfacing has proven to be an effective
means of extending part life by three to eight times.
8.1.1.2 In
many cases, new parts which are destined for destructive wear, are hardfaced
before being put into service initially.
Savings are effected by reclaiming worn parts, reduc-
ing maintenance and replacement costs,
and permitting the use of relatively inexpensive base
metals. 8.1.1.3
Shops specializing in hardfacing are
set up for automatic operation in many cases.
Jigs, fixtures, and rotating devices are often used for economical surfacing
of large numbers
of parts. Parts which are large and costly to disassemble, such as power
shovel buckets,
can be hardsurfaced on site without dismantling the equipment, using semiauto-
matic or manual arc welding.
8.1.1.4 Various
hardfacing and build-up alloys have been designed to perform specific
functions with predictable results.
The selection of the proper hardfacing alloys requires a
knowledge of:
1. The wear factors under which
it must operate. 2.
The function of the part or equipment. 3.
The base metal to which it must be applied. (Note:
Hardfacing and hard surfacing are synonymous terms.)
