Hi bhellman
A revised list of coating hardness. Memory obviously not quite so good
Hardness values from a few of my old lab reports. The examples may not necessarily be typical of the coating type though
The relationship between cross-sectional microhardness and superficial Rockwell (also effecting conversion to HRC) tends not to be very consistent, particularly between different coating types. Hope this helps.
Plasma sprayed chromium oxide
1800 HV/0.3 96.5 HR15N (79-80 HRC
converted)
1500 HV/0.3 95.5 - 96 HR15N (75-76 HRC converted)
1250 HV/0.3 94.5 - 95 HR15N (71-72 HRC converted)
Chromium oxide, alumina, alumina/titania
1000 HV/0.3 92 - 93 HR15N (64-69 HRC converted)
740-1050 HV/0.3 89.5 HR15N
850 HV/1 88 HR15N
HVOF WC/Co, WC/CoCr
700 HV/0.3 86 HR15N (52 HRC converted from HR15N, 60 HRC from HV)
900 HV/0.3 90 HR15N (55-60 HRC claimed in lit.)
900 HV/0.3 - (63-66 HRC claimed in lit.)
1250 HV/0.3 92 .5 HR15N (66-72 HRC converted)
Plasma WC/12Co
780 HV/0.3 87 HR15N (53 HRC converted from HR15N, 63 HRC converted from HV)
1000 HV/0.3 90 HR15N (60 HRC converted from HR15N, 69 HRC converted from HV)
Chromium carbide/25% nickel chromium alloy
990 HV/0.3 89 HR15N (58 HRC converted from HR15N, 69 HRC converted from HV)
750 HV0.3 - (55 HRC claimed in lit. 62 HRC converted from HV)
Generally as a rough guide (range relative to grade and quality)
Chromium oxide coatings 1000 - 1800 HV (92 - 96.5 HR15N)
Alumina and Alumina/titania 750 - 1250 HV (87 - 92 HR15N)
WC/Co and WC/CoCr 750 - 1450 HV (86 - 93 HR15N)
Chromium carbide/NiCr 600 ? 1100 HV (85 ? 90 HR15N)