metal based alloy intermetallic or other material exemplary refractory metals are mo nb ta and w these may be obtained as wire or sheet stock and cut and shaped as appropriate a coating system includes a base layer 52 initially deposited atop the substrate although shown discretely for purposes of illustration in an exemplary embodiment the base layer material becomes diffused into the substrate material an intermediate layer 54 is atop the base layer and an outer layer 56 is atop the intermediate layer the exemplary outer and outermost layer 56 may provide a combination of chemical protection mechanical protection and thermal insulation e g acting as a substantial barrier to infiltration of casting metal that might alloy with or otherwise attack the substrate and to oxygen to prevent oxidation exemplary outer layer materials are ceramics e g aluminum oxide alumina mullite silicon dioxide silica and magnesium oxide magnesia built up by deposition e g chemical vapor deposition cvd the exemplary intermediate layer 54 may serve principally as a bonding layer for good adherence of the outer layer 56 the intermediate layer may also provide a backup or additional barrier against oxygen exemplary intermediate layer materials are carbides or nitrides e g titanium carbide built up by deposition e g cvd such materials are advantageously stable at outer layer deposition temperatures in the range of.