Optical Microscope Examinations

of Two A-286 Alloy Collars,

Y-63700-18-1

William C. Ferguson

Material & Process Development

April 8, 2014

Summary of Examinations Two, A-286 alloy P/N Y-63700-18-1 collars were sectioned to allow visual and

optical microscope examination of wear patterns on the 0.877/0.875 inch

diameter cylinders. The collars were gas nitrided at Surface Treating of Ohio to

produce a case depth of 0.003 inch. The collars are believed to have operated

in separate down well environments for an undisclosed period of time.

The received collars, identified as “A” and “B”, were sectioned axially through

the 0.55/0.54 inch diameter center land which separates the two cylinders, and

along a center longitudinal plane to expose the cylinder surfaces for

examination. Figure 1 shows the sectioned pieces of cylinder “A” arranged in

situ, revealing the wear patterns in cylinders identified as A1/A2 and A3/A4.

Cylinder A1/A2 exhibited uniform wear on the center land side face that

presumably contacted the piston. On the cylinder surface there were four

significantly worn cylindrical bands, shown in Figure 2. The condition of the

wear bands were uniform over 360°; wear band widths, in order from the center

land, measured 3.5, 2.5, 3.0, and 2.7 mm. The maximum amount of wear

occurred in the band proximate to the center land, the amount of material loss

evident in the magnified view of the cylinder cross-section edge in Figure 3.

The degree of wear within this band is believed to have completely removed

the nitrided case. Each wear band exhibited a relatively smooth finish with fine

Summary cont.(p.2/4) longitudinal scratch marks; there was no evidence of case crushing by high

radial loads exerted by the mating piston. These wear patterns are consistent

with the abrasive action of fine particles present between the oscillating piston

and cylinder.

Cylinder A3/A4 from collar “A”, shown in Figure 4, displayed nonuniform wear

of the center land side face: Approximately 120° of the center land was

significantly reduced in thickness and exhibited a deformed edge. These

features are clearly shown in the magnified images in Figure 5. The cylinder

surface contained four predominant wear bands with widths that varied

significantly over 360°, features indicative of misalignment of the piston relative

to the cylinder axis. Average wear band width, in order from the center land,

measured 7, 7, 3, and 7 mm. The surface of the cylinder wear bands was

similar in condition to the wear bands of the A1/A2 companion cylinder.

The collar “B” sections are arranged in situ in Figure 6. Wear bands present in

the two cylinders appear more reflective than the wear bands of collar “A”.

Cylinder B1/B2, shown in Figure 7, exhibits uniform wear on the center land.

Several wear bands present on the cylinder surface are uniform in width over

360° indicating alignment of the piston with the cylinder. The largest

Summary cont.(p.3/4) band was 7 mm in width, the smallest 1.5 mm wide. Surveys of the wear

bands at 20 to 50x magnification determined that the surfaces were glazed with

longitudinal scratch marks, a condition that would account for the higher

reflectivity of the surface and suggestive of superficial smearing of the surface

concurrent with abrasion by hard particles. These characteristics are shown in

Figure 8. Examination of the edge of the cylinder cross-section edge revealed

that cylinder B1/B2 exhibited the least amount of wear among the four

cylinders.

Companion cylinder B3/B4 is shown in Figure 9. It also experienced uniform

wear on the center land side face; in addition, the center land edge is deformed

presumably as a result of contact with the piston, the deformation evident in the

bottom-left inset of Figure 10. The cylinder surface contained three major wear

bands measuring, in order from the center land, 4, 4, and 1.5 mm in width. At

20 to 50x magnification these bands were found to have a glazed condition and

longitudinal scratches similar to that observed in the cylinder B1/B2 wear

bands. Wear band width and surface condition was constant over 360°,

evidence that the piston was aligned with the cylinder axis during operation.

The greatest amount of wear occurred in the 4 mm wide band that adjoined the

1.5 mm band, evident in the top-right inset of Figure 10.

Summary cont.(p.4/4) CONCLUSIONS:

1. The cylinder surfaces had experienced significant wear within several

cylindrical bands indicating that the 0.003-inch nitrided case depth was

inadequate to provide satisfactory wear resistance during operation.

Selected locations of the collars will be metallographically prepared for

evaluation of the original nitrided case depth and hardness, and

examination of the wear band surface condition, both the dull and glazed

conditions. To augment wear resistance it is advised to process future part

lots with a 0.008 to 0.010 case depth, commensurate with case depths

specified for gears.

2. One of the four cylinders examined displayed evidence of misalignment

between the piston and the cylinder axis.

3. Wear patterns were characteristic of hard abrasive particles present

between the piston and cylinder wall, but the glazed condition in the collar

“B” cylinders indicates that some superficial deformation of the cylinder wall

had occurred, possibly by metal-to-metal contact.

Figure 1. Longitudinal cross-section of Y-63700-18-1 collar identified as “A”:

A1/A2 cylinder shown on left; A3/A4 cylinder on right.

A1

A2

A3

A4

A1 A1

Figure 2. Longitudinal cross-sections of the A1/A2 cylinder from collar “A”:

Profile views (left); and oblique views (right). Four predominant wear bands

are identified by arrows.

A2

A2

A1

Figure 3. Magnified view of

sectioned edge of A1/A2

cylinder from collar “A”

revealing the amount of wear

experienced (arrows).

Original inset magnification of

20x.

Figure 4. Longitudinal cross-sections of the A3/A4 cylinder from collar “A”:

Profile views (left); and oblique views (right). Green arrows identify thin wall

section of center land; red arrows identify four predominant wear bands.

A3

A3

A4 A4

Figure 5. Magnified view of

sectioned edge of A3/A4 cylinder

from collar “A” revealing a

concentration of wear on one side of

the land side face (above right) and a

deformed edge. Original inset

magnification of 20x.

A3

Figure 6. Longitudinal cross-section of Y-63700-18-1 collar identified as “B”:

B1/B2 cylinder shown on left; B3/B4 cylinder is on right.

B1 B3

B2 B4

Figure 7. Longitudinal cross-sections of the B1/B2 cylinder from collar “B”:

Profile views (left); and oblique views (right).

B1 B1

B2

B2

B1

Figure 8. Magnified view of

sectioned edge of B1/B2 cylinder

from collar “B” revealing glazed

bands with longitudinal striations.

Original inset magnifications of 20x.

Figure 9. Longitudinal cross-sections of the B3/B4 cylinder from collar “B”:

Profile views (left); and oblique views (right).

B3

B3

B4 B4

B3

Figure 10. Magnified views of

sectioned edge of B3/B4 cylinder

from collar “B” showing details of

wear bands and deformed edge of

center land (yellow arrow). Original

inset magnifications of 20x.

4 mm wear band